X-Git-Url: https://git.openssl.org/gitweb/?p=openssl.git;a=blobdiff_plain;f=crypto%2Fperlasm%2Fx86_64-xlate.pl;h=885690507ecf53e6279ea17a105aec9a706e6768;hp=b158f72971a1678be7dd3cb0f1f51ff76f100e7a;hb=4e3d2866b6e8e7a700ea22e05840a093bfd7a4b1;hpb=6a3a7f3076354a4c2414b16f7fa1b76d5e4174d2

diff --git a/crypto/perlasm/x86_64-xlate.pl b/crypto/perlasm/x86_64-xlate.pl
index b158f72971..885690507e 100755
--- a/crypto/perlasm/x86_64-xlate.pl
+++ b/crypto/perlasm/x86_64-xlate.pl
@@ -1,6 +1,13 @@
-#!/usr/bin/env perl
+#! /usr/bin/env perl
+# Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the OpenSSL license (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
 
-# Ascetic x86_64 AT&T to MASM assembler translator by <appro>.
+# Ascetic x86_64 AT&T to MASM/NASM assembler translator by <appro>.
 #
 # Why AT&T to MASM and not vice versa? Several reasons. Because AT&T
 # format is way easier to parse. Because it's simpler to "gear" from
@@ -20,12 +27,11 @@
 # Currently recognized limitations:
 #
 # - can't use multiple ops per line;
-# - indirect calls and jumps are not supported;
 #
 # Dual-ABI styling rules.
 #
-# 1. Adhere to Unix register and stack layout [see the end for
-#    explanation].
+# 1. Adhere to Unix register and stack layout [see cross-reference
+#    ABI "card" at the end for explanation].
 # 2. Forget about "red zone," stick to more traditional blended
 #    stack frame allocation. If volatile storage is actually required
 #    that is. If not, just leave the stack as is.
@@ -42,44 +48,93 @@
 # 6. Don't use [or hand-code with .byte] "rep ret." "ret" mnemonic is
 #    required to identify the spots, where to inject Win64 epilogue!
 #    But on the pros, it's then prefixed with rep automatically:-)
-# 7. Due to MASM limitations [and certain general counter-intuitivity
-#    of ip-relative addressing] generation of position-independent
-#    code is assisted by synthetic directive, .picmeup, which puts
-#    address of the *next* instruction into target register.
+# 7. Stick to explicit ip-relative addressing. If you have to use
+#    GOTPCREL addressing, stick to mov symbol@GOTPCREL(%rip),%r??.
+#    Both are recognized and translated to proper Win64 addressing
+#    modes. To support legacy code a synthetic directive, .picmeup,
+#    is implemented. It puts address of the *next* instruction into
+#    target register, e.g.:
 #
-#    Example 1:
 #		.picmeup	%rax
 #		lea		.Label-.(%rax),%rax
-#    Example 2:
-#		.picmeup	%rcx
-#	.Lpic_point:
-#		...
-#		lea		.Label-.Lpic_point(%rcx),%rbp
+#
+# 8. In order to provide for structured exception handling unified
+#    Win64 prologue copies %rsp value to %rax. For further details
+#    see SEH paragraph at the end.
+# 9. .init segment is allowed to contain calls to functions only.
+# a. If function accepts more than 4 arguments *and* >4th argument
+#    is declared as non 64-bit value, do clear its upper part.
+
+
+use strict;
+
+my $flavour = shift;
+my $output  = shift;
+if ($flavour =~ /\./) { $output = $flavour; undef $flavour; }
 
-my $output = shift;
-open STDOUT,">$output" || die "can't open $output: $!";
+open STDOUT,">$output" || die "can't open $output: $!"
+	if (defined($output));
 
-my $masm=1 if ($output =~ /\.asm/);
+my $gas=1;	$gas=0 if ($output =~ /\.asm$/);
+my $elf=1;	$elf=0 if (!$gas);
+my $win64=0;
+my $prefix="";
+my $decor=".L";
+
+my $masmref=8 + 50727*2**-32;	# 8.00.50727 shipped with VS2005
+my $masm=0;
+my $PTR=" PTR";
+
+my $nasmref=2.03;
+my $nasm=0;
+
+if    ($flavour eq "mingw64")	{ $gas=1; $elf=0; $win64=1;
+				  $prefix=`echo __USER_LABEL_PREFIX__ | $ENV{CC} -E -P -`;
+				  $prefix =~ s|\R$||; # Better chomp
+				}
+elsif ($flavour eq "macosx")	{ $gas=1; $elf=0; $prefix="_"; $decor="L\$"; }
+elsif ($flavour eq "masm")	{ $gas=0; $elf=0; $masm=$masmref; $win64=1; $decor="\$L\$"; }
+elsif ($flavour eq "nasm")	{ $gas=0; $elf=0; $nasm=$nasmref; $win64=1; $decor="\$L\$"; $PTR=""; }
+elsif (!$gas)
+{   if ($ENV{ASM} =~ m/nasm/ && `nasm -v` =~ m/version ([0-9]+)\.([0-9]+)/i)
+    {	$nasm = $1 + $2*0.01; $PTR="";  }
+    elsif (`ml64 2>&1` =~ m/Version ([0-9]+)\.([0-9]+)(\.([0-9]+))?/)
+    {	$masm = $1 + $2*2**-16 + $4*2**-32;   }
+    die "no assembler found on %PATH" if (!($nasm || $masm));
+    $win64=1;
+    $elf=0;
+    $decor="\$L\$";
+}
 
 my $current_segment;
 my $current_function;
+my %globals;
 
 { package opcode;	# pick up opcodes
     sub re {
-	my	$self = shift;	# single instance in enough...
-	local	*line = shift;
-	undef	$ret;
+	my	($class, $line) = @_;
+	my	$self = {};
+	my	$ret;
 
-	if ($line =~ /^([a-z]+)/i) {
+	if ($$line =~ /^([a-z][a-z0-9]*)/i) {
+	    bless $self,$class;
 	    $self->{op} = $1;
 	    $ret = $self;
-	    $line = substr($line,@+[0]); $line =~ s/^\s+//;
+	    $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 
 	    undef $self->{sz};
-	    if ($self->{op} =~ /(movz)b.*/) {	# movz is pain...
+	    if ($self->{op} =~ /^(movz)x?([bw]).*/) {	# movz is pain...
 		$self->{op} = $1;
-		$self->{sz} = "b";
-	    } elsif ($self->{op} =~ /([a-z]{3,})([qlwb])/) {
+		$self->{sz} = $2;
+	    } elsif ($self->{op} =~ /call|jmp/) {
+		$self->{sz} = "";
+	    } elsif ($self->{op} =~ /^p/ && $' !~ /^(ush|op|insrw)/) { # SSEn
+		$self->{sz} = "";
+	    } elsif ($self->{op} =~ /^v/) { # VEX
+		$self->{sz} = "";
+	    } elsif ($self->{op} =~ /mov[dq]/ && $$line =~ /%xmm/) {
+		$self->{sz} = "";
+	    } elsif ($self->{op} =~ /([a-z]{3,})([qlwb])$/) {
 		$self->{op} = $1;
 		$self->{sz} = $2;
 	    }
@@ -87,85 +142,117 @@ my $current_function;
 	$ret;
     }
     sub size {
-	my $self = shift;
-	my $sz   = shift;
+	my ($self, $sz) = @_;
 	$self->{sz} = $sz if (defined($sz) && !defined($self->{sz}));
 	$self->{sz};
     }
     sub out {
 	my $self = shift;
-	if (!$masm) {
-	    if ($self->{op} eq "movz") {	# movz in pain...
+	if ($gas) {
+	    if ($self->{op} eq "movz") {	# movz is pain...
 		sprintf "%s%s%s",$self->{op},$self->{sz},shift;
+	    } elsif ($self->{op} =~ /^set/) { 
+		"$self->{op}";
 	    } elsif ($self->{op} eq "ret") {
-	    	".byte	0xf3,0xc3";
+		my $epilogue = "";
+		if ($win64 && $current_function->{abi} eq "svr4") {
+		    $epilogue = "movq	8(%rsp),%rdi\n\t" .
+				"movq	16(%rsp),%rsi\n\t";
+		}
+	    	$epilogue . ".byte	0xf3,0xc3";
+	    } elsif ($self->{op} eq "call" && !$elf && $current_segment eq ".init") {
+		".p2align\t3\n\t.quad";
 	    } else {
 		"$self->{op}$self->{sz}";
 	    }
 	} else {
-	    $self->{op} =~ s/movz/movzx/;
+	    $self->{op} =~ s/^movz/movzx/;
 	    if ($self->{op} eq "ret") {
 		$self->{op} = "";
-		if ($current_function->{abi} eq "svr4") {
-		    $self->{op} = "mov	rdi,QWORD PTR 8[rsp]\t;WIN64 epilogue\n\t".
-				  "mov	rsi,QWORD PTR 16[rsp]\n\t";
+		if ($win64 && $current_function->{abi} eq "svr4") {
+		    $self->{op} = "mov	rdi,QWORD${PTR}[8+rsp]\t;WIN64 epilogue\n\t".
+				  "mov	rsi,QWORD${PTR}[16+rsp]\n\t";
 	    	}
 		$self->{op} .= "DB\t0F3h,0C3h\t\t;repret";
-	    }
+	    } elsif ($self->{op} =~ /^(pop|push)f/) {
+		$self->{op} .= $self->{sz};
+	    } elsif ($self->{op} eq "call" && $current_segment eq ".CRT\$XCU") {
+		$self->{op} = "\tDQ";
+	    } 
 	    $self->{op};
 	}
     }
+    sub mnemonic {
+	my ($self, $op) = @_;
+	$self->{op}=$op if (defined($op));
+	$self->{op};
+    }
 }
 { package const;	# pick up constants, which start with $
     sub re {
-	my	$self = shift;	# single instance in enough...
-	local	*line = shift;
-	undef	$ret;
+	my	($class, $line) = @_;
+	my	$self = {};
+	my	$ret;
 
-	if ($line =~ /^\$([^,]+)/) {
+	if ($$line =~ /^\$([^,]+)/) {
+	    bless $self, $class;
 	    $self->{value} = $1;
 	    $ret = $self;
-	    $line = substr($line,@+[0]); $line =~ s/^\s+//;
+	    $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 	}
 	$ret;
     }
     sub out {
     	my $self = shift;
 
-	if (!$masm) {
+	$self->{value} =~ s/\b(0b[0-1]+)/oct($1)/eig;
+	if ($gas) {
 	    # Solaris /usr/ccs/bin/as can't handle multiplications
 	    # in $self->{value}
-	    $self->{value} =~ s/(?<![0-9a-f])(0[x0-9a-f]+)/oct($1)/egi;
-	    $self->{value} =~ s/([0-9]+\s*[\*\/\%]\s*[0-9]+)/eval($1)/eg;
+	    my $value = $self->{value};
+	    $value =~ s/(?<![\w\$\.])(0x?[0-9a-f]+)/oct($1)/egi;
+	    if ($value =~ s/([0-9]+\s*[\*\/\%]\s*[0-9]+)/eval($1)/eg) {
+		$self->{value} = $value;
+	    }
 	    sprintf "\$%s",$self->{value};
 	} else {
-	    $self->{value} =~ s/0x([0-9a-f]+)/0$1h/ig;
+	    $self->{value} =~ s/0x([0-9a-f]+)/0$1h/ig if ($masm);
 	    sprintf "%s",$self->{value};
 	}
     }
 }
 { package ea;		# pick up effective addresses: expr(%reg,%reg,scale)
     sub re {
-	my	$self = shift;	# single instance in enough...
-	local	*line = shift;
-	undef	$ret;
+	my	($class, $line, $opcode) = @_;
+	my	$self = {};
+	my	$ret;
 
-	if ($line =~ /^([^\(,]*)\(([%\w,]+)\)/) {
-	    $self->{label} = $1;
-	    ($self->{base},$self->{index},$self->{scale})=split(/,/,$2);
+	# optional * ---vvv--- appears in indirect jmp/call
+	if ($$line =~ /^(\*?)([^\(,]*)\(([%\w,]+)\)/) {
+	    bless $self, $class;
+	    $self->{asterisk} = $1;
+	    $self->{label} = $2;
+	    ($self->{base},$self->{index},$self->{scale})=split(/,/,$3);
 	    $self->{scale} = 1 if (!defined($self->{scale}));
 	    $ret = $self;
-	    $line = substr($line,@+[0]); $line =~ s/^\s+//;
+	    $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 
+	    if ($win64 && $self->{label} =~ s/\@GOTPCREL//) {
+		die if ($opcode->mnemonic() ne "mov");
+		$opcode->mnemonic("lea");
+	    }
 	    $self->{base}  =~ s/^%//;
 	    $self->{index} =~ s/^%// if (defined($self->{index}));
+	    $self->{opcode} = $opcode;
 	}
 	$ret;
     }
     sub size {}
     sub out {
-    	my $self = shift;
-	my $sz = shift;
+	my ($self, $sz) = @_;
+
+	$self->{label} =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
+	$self->{label} =~ s/\.L/$decor/g;
 
 	# Silently convert all EAs to 64-bit. This is required for
 	# elder GNU assembler and results in more compact code,
@@ -173,56 +260,81 @@ my $current_function;
 	$self->{index} =~ s/^[er](.?[0-9xpi])[d]?$/r\1/;
 	$self->{base}  =~ s/^[er](.?[0-9xpi])[d]?$/r\1/;
 
-	if (!$masm) {
-	    # Solaris /usr/ccs/bin/as can't handle multiplications
-	    # in $self->{label}
-	    $self->{label} =~ s/(?<![0-9a-f])(0[x0-9a-f]+)/oct($1)/egi;
-	    $self->{label} =~ s/([0-9]+\s*[\*\/\%]\s*[0-9]+)/eval($1)/eg;
+	# Solaris /usr/ccs/bin/as can't handle multiplications
+	# in $self->{label}, new gas requires sign extension...
+	use integer;
+	$self->{label} =~ s/(?<![\w\$\.])(0x?[0-9a-f]+)/oct($1)/egi;
+	$self->{label} =~ s/\b([0-9]+\s*[\*\/\%]\s*[0-9]+)\b/eval($1)/eg;
+	$self->{label} =~ s/\b([0-9]+)\b/$1<<32>>32/eg;
+
+	if (!$self->{label} && $self->{index} && $self->{scale}==1 &&
+	    $self->{base} =~ /(rbp|r13)/) {
+		$self->{base} = $self->{index}; $self->{index} = $1;
+	}
+
+	if ($gas) {
+	    $self->{label} =~ s/^___imp_/__imp__/   if ($flavour eq "mingw64");
 
 	    if (defined($self->{index})) {
-		sprintf "%s(%%%s,%%%s,%d)",
-					$self->{label},$self->{base},
+		sprintf "%s%s(%s,%%%s,%d)",$self->{asterisk},
+					$self->{label},
+					$self->{base}?"%$self->{base}":"",
 					$self->{index},$self->{scale};
 	    } else {
-		sprintf "%s(%%%s)",	$self->{label},$self->{base};
+		sprintf "%s%s(%%%s)",	$self->{asterisk},$self->{label},$self->{base};
 	    }
 	} else {
-	    %szmap = ( b=>"BYTE", w=>"WORD", l=>"DWORD", q=>"QWORD" );
+	    my %szmap = (	b=>"BYTE$PTR",  w=>"WORD$PTR",
+			l=>"DWORD$PTR", d=>"DWORD$PTR",
+	    		q=>"QWORD$PTR", o=>"OWORD$PTR",
+			x=>"XMMWORD$PTR", y=>"YMMWORD$PTR", z=>"ZMMWORD$PTR" );
 
 	    $self->{label} =~ s/\./\$/g;
-	    $self->{label} =~ s/0x([0-9a-f]+)/0$1h/ig;
+	    $self->{label} =~ s/(?<![\w\$\.])0x([0-9a-f]+)/0$1h/ig;
 	    $self->{label} = "($self->{label})" if ($self->{label} =~ /[\*\+\-\/]/);
 
+	    my $mnemonic = $self->{opcode}->mnemonic();
+	    ($self->{asterisk})				&& ($sz="q") ||
+	    ($mnemonic =~ /^v?mov([qd])$/)		&& ($sz=$1)  ||
+	    ($mnemonic =~ /^v?pinsr([qdwb])$/)		&& ($sz=$1)  ||
+	    ($mnemonic =~ /^vpbroadcast([qdwb])$/)	&& ($sz=$1)  ||
+	    ($mnemonic =~ /^v(?!perm)[a-z]+[fi]128$/)	&& ($sz="x");
+
 	    if (defined($self->{index})) {
-		sprintf "%s PTR %s[%s*%d+%s]",$szmap{$sz},
-					$self->{label},
+		sprintf "%s[%s%s*%d%s]",$szmap{$sz},
+					$self->{label}?"$self->{label}+":"",
 					$self->{index},$self->{scale},
-					$self->{base};
+					$self->{base}?"+$self->{base}":"";
+	    } elsif ($self->{base} eq "rip") {
+		sprintf "%s[%s]",$szmap{$sz},$self->{label};
 	    } else {
-		sprintf "%s PTR %s[%s]",$szmap{$sz},
-					$self->{label},$self->{base};
+		sprintf "%s[%s%s]",$szmap{$sz},
+					$self->{label}?"$self->{label}+":"",
+					$self->{base};
 	    }
 	}
     }
 }
 { package register;	# pick up registers, which start with %.
     sub re {
-	my	$class = shift;	# muliple instances...
+	my	($class, $line, $opcode) = @_;
 	my	$self = {};
-	local	*line = shift;
-	undef	$ret;
+	my	$ret;
 
-	if ($line =~ /^%(\w+)/) {
+	# optional * ----vvv--- appears in indirect jmp/call
+	if ($$line =~ /^(\*?)%(\w+)/) {
 	    bless $self,$class;
-	    $self->{value} = $1;
+	    $self->{asterisk} = $1;
+	    $self->{value} = $2;
+	    $opcode->size($self->size());
 	    $ret = $self;
-	    $line = substr($line,@+[0]); $line =~ s/^\s+//;
+	    $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 	}
 	$ret;
     }
     sub size {
 	my	$self = shift;
-	undef	$ret;
+	my	$ret;
 
 	if    ($self->{value} =~ /^r[\d]+b$/i)	{ $ret="b"; }
 	elsif ($self->{value} =~ /^r[\d]+w$/i)	{ $ret="w"; }
@@ -237,74 +349,111 @@ my $current_function;
     }
     sub out {
     	my $self = shift;
-	sprintf $masm?"%s":"%%%s",$self->{value};
+	if ($gas)	{ sprintf "%s%%%s",$self->{asterisk},$self->{value}; }
+	else		{ $self->{value}; }
     }
 }
 { package label;	# pick up labels, which end with :
     sub re {
-	my	$self = shift;	# single instance is enough...
-	local	*line = shift;
-	undef	$ret;
+	my	($class, $line) = @_;
+	my	$self = {};
+	my	$ret;
 
-	if ($line =~ /(^[\.\w]+\:)/) {
+	if ($$line =~ /(^[\.\w]+)\:/) {
+	    bless $self,$class;
 	    $self->{value} = $1;
 	    $ret = $self;
-	    $line = substr($line,@+[0]); $line =~ s/^\s+//;
+	    $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 
-	    $self->{value} =~ s/\.L/\$L/ if ($masm);
+	    $self->{value} =~ s/^\.L/$decor/;
 	}
 	$ret;
     }
     sub out {
 	my $self = shift;
 
-	if (!$masm) {
-	    $self->{value};
-	} elsif ($self->{value} ne "$current_function->{name}:") {
-	    $self->{value};
-	} elsif ($current_function->{abi} eq "svr4") {
-	    my $func =	"$current_function->{name}	PROC\n".
-			"	mov	QWORD PTR 8[rsp],rdi\t;WIN64 prologue\n".
-			"	mov	QWORD PTR 16[rsp],rsi\n";
+	if ($gas) {
+	    my $func = ($globals{$self->{value}} or $self->{value}) . ":";
+	    if ($win64	&&
+			$current_function->{name} eq $self->{value} &&
+			$current_function->{abi} eq "svr4") {
+		$func .= "\n";
+		$func .= "	movq	%rdi,8(%rsp)\n";
+		$func .= "	movq	%rsi,16(%rsp)\n";
+		$func .= "	movq	%rsp,%rax\n";
+		$func .= "${decor}SEH_begin_$current_function->{name}:\n";
+		my $narg = $current_function->{narg};
+		$narg=6 if (!defined($narg));
+		$func .= "	movq	%rcx,%rdi\n" if ($narg>0);
+		$func .= "	movq	%rdx,%rsi\n" if ($narg>1);
+		$func .= "	movq	%r8,%rdx\n"  if ($narg>2);
+		$func .= "	movq	%r9,%rcx\n"  if ($narg>3);
+		$func .= "	movq	40(%rsp),%r8\n" if ($narg>4);
+		$func .= "	movq	48(%rsp),%r9\n" if ($narg>5);
+	    }
+	    $func;
+	} elsif ($self->{value} ne "$current_function->{name}") {
+	    # Make all labels in masm global.
+	    $self->{value} .= ":" if ($masm);
+	    $self->{value} . ":";
+	} elsif ($win64 && $current_function->{abi} eq "svr4") {
+	    my $func =	"$current_function->{name}" .
+			($nasm ? ":" : "\tPROC $current_function->{scope}") .
+			"\n";
+	    $func .= "	mov	QWORD${PTR}[8+rsp],rdi\t;WIN64 prologue\n";
+	    $func .= "	mov	QWORD${PTR}[16+rsp],rsi\n";
+	    $func .= "	mov	rax,rsp\n";
+	    $func .= "${decor}SEH_begin_$current_function->{name}:";
+	    $func .= ":" if ($masm);
+	    $func .= "\n";
 	    my $narg = $current_function->{narg};
 	    $narg=6 if (!defined($narg));
 	    $func .= "	mov	rdi,rcx\n" if ($narg>0);
 	    $func .= "	mov	rsi,rdx\n" if ($narg>1);
 	    $func .= "	mov	rdx,r8\n"  if ($narg>2);
 	    $func .= "	mov	rcx,r9\n"  if ($narg>3);
-	    $func .= "	mov	r8,QWORD PTR 40[rsp]\n" if ($narg>4);
-	    $func .= "	mov	r9,QWORD PTR 48[rsp]\n" if ($narg>5);
+	    $func .= "	mov	r8,QWORD${PTR}[40+rsp]\n" if ($narg>4);
+	    $func .= "	mov	r9,QWORD${PTR}[48+rsp]\n" if ($narg>5);
 	    $func .= "\n";
 	} else {
-	   "$current_function->{name}	PROC";
+	   "$current_function->{name}".
+			($nasm ? ":" : "\tPROC $current_function->{scope}");
 	}
     }
 }
 { package expr;		# pick up expressioins
     sub re {
-	my	$self = shift;	# single instance is enough...
-	local	*line = shift;
-	undef	$ret;
+	my	($class, $line, $opcode) = @_;
+	my	$self = {};
+	my	$ret;
 
-	if ($line =~ /(^[^,]+)/) {
+	if ($$line =~ /(^[^,]+)/) {
+	    bless $self,$class;
 	    $self->{value} = $1;
 	    $ret = $self;
-	    $line = substr($line,@+[0]); $line =~ s/^\s+//;
+	    $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 
-	    $self->{value} =~ s/\.L/\$L/g if ($masm);
+	    $self->{value} =~ s/\@PLT// if (!$elf);
+	    $self->{value} =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
+	    $self->{value} =~ s/\.L/$decor/g;
+	    $self->{opcode} = $opcode;
 	}
 	$ret;
     }
     sub out {
 	my $self = shift;
-	$self->{value};
+	if ($nasm && $self->{opcode}->mnemonic()=~m/^j(?![re]cxz)/) {
+	    "NEAR ".$self->{value};
+	} else {
+	    $self->{value};
+	}
     }
 }
 { package directive;	# pick up directives, which start with .
     sub re {
-	my	$self = shift;	# single instance is enough...
-	local	*line = shift;
-	undef	$ret;
+	my	($class, $line) = @_;
+	my	$self = {};
+	my	$ret;
 	my	$dir;
 	my	%opcode =	# lea 2f-1f(%rip),%dst; 1: nop; 2:
 		(	"%rax"=>0x01058d48,	"%rcx"=>0x010d8d48,
@@ -316,70 +465,214 @@ my $current_function;
 			"%r12"=>0x01258d4c,	"%r13"=>0x012d8d4c,
 			"%r14"=>0x01358d4c,	"%r15"=>0x013d8d4c	);
 
-	if ($line =~ /^\s*(\.\w+)/) {
-	    if (!$masm) {
-		$self->{value} = $1;
-		$line =~ s/\@abi\-omnipotent/\@function/;
-		$line =~ s/\@function.*/\@function/;
-		if ($line =~ /\.picmeup\s+(%r[\w]+)/i) {
-		    $self->{value} = sprintf "\t.long\t0x%x,0x90000000",$opcode{$1};
-		} else {
-		    $self->{value} = $line;
-		}
-		$line = "";
-		return $self;
-	    }
-
+	if ($$line =~ /^\s*(\.\w+)/) {
+	    bless $self,$class;
 	    $dir = $1;
 	    $ret = $self;
 	    undef $self->{value};
-	    $line = substr($line,@+[0]); $line =~ s/^\s+//;
+	    $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
+
 	    SWITCH: for ($dir) {
-		/\.(text)/
-			    && do { my $v=undef;
-				    $v="$current_segment\tENDS\n" if ($current_segment);
-				    $current_segment = "_$1\$";
-				    $current_segment =~ tr/[a-z]/[A-Z]/;
-				    $v.="$current_segment\tSEGMENT ALIGN(64) 'CODE'";
-				    $self->{value} = $v;
+		/\.picmeup/ && do { if ($$line =~ /(%r[\w]+)/i) {
+			    		$dir="\t.long";
+					$$line=sprintf "0x%x,0x90000000",$opcode{$1};
+				    }
+				    last;
+				  };
+		/\.global|\.globl|\.extern/
+			    && do { $globals{$$line} = $prefix . $$line;
+				    $$line = $globals{$$line} if ($prefix);
 				    last;
 				  };
-		/\.globl/   && do { $self->{value} = "PUBLIC\t".$line; last; };
-		/\.type/    && do { ($sym,$type,$narg) = split(',',$line);
+		/\.type/    && do { my ($sym,$type,$narg) = split(',',$$line);
 				    if ($type eq "\@function") {
 					undef $current_function;
 					$current_function->{name} = $sym;
 					$current_function->{abi}  = "svr4";
 					$current_function->{narg} = $narg;
+					$current_function->{scope} = defined($globals{$sym})?"PUBLIC":"PRIVATE";
 				    } elsif ($type eq "\@abi-omnipotent") {
 					undef $current_function;
 					$current_function->{name} = $sym;
+					$current_function->{scope} = defined($globals{$sym})?"PUBLIC":"PRIVATE";
+				    }
+				    $$line =~ s/\@abi\-omnipotent/\@function/;
+				    $$line =~ s/\@function.*/\@function/;
+				    last;
+				  };
+		/\.asciz/   && do { if ($$line =~ /^"(.*)"$/) {
+					$dir  = ".byte";
+					$$line = join(",",unpack("C*",$1),0);
+				    }
+				    last;
+				  };
+		/\.rva|\.long|\.quad/
+			    && do { $$line =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
+				    $$line =~ s/\.L/$decor/g;
+				    last;
+				  };
+	    }
+
+	    if ($gas) {
+		$self->{value} = $dir . "\t" . $$line;
+
+		if ($dir =~ /\.extern/) {
+		    $self->{value} = ""; # swallow extern
+		} elsif (!$elf && $dir =~ /\.type/) {
+		    $self->{value} = "";
+		    $self->{value} = ".def\t" . ($globals{$1} or $1) . ";\t" .
+				(defined($globals{$1})?".scl 2;":".scl 3;") .
+				"\t.type 32;\t.endef"
+				if ($win64 && $$line =~ /([^,]+),\@function/);
+		} elsif (!$elf && $dir =~ /\.size/) {
+		    $self->{value} = "";
+		    if (defined($current_function)) {
+			$self->{value} .= "${decor}SEH_end_$current_function->{name}:"
+				if ($win64 && $current_function->{abi} eq "svr4");
+			undef $current_function;
+		    }
+		} elsif (!$elf && $dir =~ /\.align/) {
+		    $self->{value} = ".p2align\t" . (log($$line)/log(2));
+		} elsif ($dir eq ".section") {
+		    $current_segment=$$line;
+		    if (!$elf && $current_segment eq ".init") {
+			if	($flavour eq "macosx")	{ $self->{value} = ".mod_init_func"; }
+			elsif	($flavour eq "mingw64")	{ $self->{value} = ".section\t.ctors"; }
+		    }
+		} elsif ($dir =~ /\.(text|data)/) {
+		    $current_segment=".$1";
+		} elsif ($dir =~ /\.hidden/) {
+		    if    ($flavour eq "macosx")  { $self->{value} = ".private_extern\t$prefix$$line"; }
+		    elsif ($flavour eq "mingw64") { $self->{value} = ""; }
+		} elsif ($dir =~ /\.comm/) {
+		    $self->{value} = "$dir\t$prefix$$line";
+		    $self->{value} =~ s|,([0-9]+),([0-9]+)$|",$1,".log($2)/log(2)|e if ($flavour eq "macosx");
+		}
+		$$line = "";
+		return $self;
+	    }
+
+	    # non-gas case or nasm/masm
+	    SWITCH: for ($dir) {
+		/\.text/    && do { my $v=undef;
+				    if ($nasm) {
+					$v="section	.text code align=64\n";
+				    } else {
+					$v="$current_segment\tENDS\n" if ($current_segment);
+					$current_segment = ".text\$";
+					$v.="$current_segment\tSEGMENT ";
+					$v.=$masm>=$masmref ? "ALIGN(256)" : "PAGE";
+					$v.=" 'CODE'";
+				    }
+				    $self->{value} = $v;
+				    last;
+				  };
+		/\.data/    && do { my $v=undef;
+				    if ($nasm) {
+					$v="section	.data data align=8\n";
+				    } else {
+					$v="$current_segment\tENDS\n" if ($current_segment);
+					$current_segment = "_DATA";
+					$v.="$current_segment\tSEGMENT";
 				    }
+				    $self->{value} = $v;
+				    last;
+				  };
+		/\.section/ && do { my $v=undef;
+				    $$line =~ s/([^,]*).*/$1/;
+				    $$line = ".CRT\$XCU" if ($$line eq ".init");
+				    if ($nasm) {
+					$v="section	$$line";
+					if ($$line=~/\.([px])data/) {
+					    $v.=" rdata align=";
+					    $v.=$1 eq "p"? 4 : 8;
+					} elsif ($$line=~/\.CRT\$/i) {
+					    $v.=" rdata align=8";
+					}
+				    } else {
+					$v="$current_segment\tENDS\n" if ($current_segment);
+					$v.="$$line\tSEGMENT";
+					if ($$line=~/\.([px])data/) {
+					    $v.=" READONLY";
+					    $v.=" ALIGN(".($1 eq "p" ? 4 : 8).")" if ($masm>=$masmref);
+					} elsif ($$line=~/\.CRT\$/i) {
+					    $v.=" READONLY ";
+					    $v.=$masm>=$masmref ? "ALIGN(8)" : "DWORD";
+					}
+				    }
+				    $current_segment = $$line;
+				    $self->{value} = $v;
+				    last;
+				  };
+		/\.extern/  && do { $self->{value}  = "EXTERN\t".$$line;
+				    $self->{value} .= ":NEAR" if ($masm);
+				    last;
+				  };
+		/\.globl|.global/
+			    && do { $self->{value}  = $masm?"PUBLIC":"global";
+				    $self->{value} .= "\t".$$line;
 				    last;
 				  };
 		/\.size/    && do { if (defined($current_function)) {
-					$self->{value}="$current_function->{name}\tENDP";
+					undef $self->{value};
+					if ($current_function->{abi} eq "svr4") {
+					    $self->{value}="${decor}SEH_end_$current_function->{name}:";
+					    $self->{value}.=":\n" if($masm);
+					}
+					$self->{value}.="$current_function->{name}\tENDP" if($masm && $current_function->{name});
 					undef $current_function;
 				    }
 				    last;
 				  };
-		/\.align/   && do { $self->{value} = "ALIGN\t".$line; last; };
-		/\.(byte|value|long|quad)/
-			    && do { my @arr = split(',',$line);
-				    my $sz  = substr($1,0,1);
+		/\.align/   && do { my $max = ($masm && $masm>=$masmref) ? 256 : 4096;
+				    $self->{value} = "ALIGN\t".($$line>$max?$max:$$line);
+				    last;
+				  };
+		/\.(value|long|rva|quad)/
+			    && do { my $sz  = substr($1,0,1);
+				    my @arr = split(/,\s*/,$$line);
 				    my $last = pop(@arr);
+				    my $conv = sub  {	my $var=shift;
+							$var=~s/^(0b[0-1]+)/oct($1)/eig;
+							$var=~s/^0x([0-9a-f]+)/0$1h/ig if ($masm);
+							if ($sz eq "D" && ($current_segment=~/.[px]data/ || $dir eq ".rva"))
+							{ $var=~s/([_a-z\$\@][_a-z0-9\$\@]*)/$nasm?"$1 wrt ..imagebase":"imagerel $1"/egi; }
+							$var;
+						    };  
 
-				    $sz =~ tr/bvlq/BWDQ/;
+				    $sz =~ tr/bvlrq/BWDDQ/;
 				    $self->{value} = "\tD$sz\t";
-				    for (@arr) { $self->{value} .= sprintf"0%Xh,",oct; }
-				    $self->{value} .= sprintf"0%Xh",oct($last);
+				    for (@arr) { $self->{value} .= &$conv($_).","; }
+				    $self->{value} .= &$conv($last);
 				    last;
 				  };
-		/\.picmeup/ && do { $self->{value} = sprintf"\tDD\t 0%Xh,090000000h",$opcode{$line};
+		/\.byte/    && do { my @str=split(/,\s*/,$$line);
+				    map(s/(0b[0-1]+)/oct($1)/eig,@str);
+				    map(s/0x([0-9a-f]+)/0$1h/ig,@str) if ($masm);	
+				    while ($#str>15) {
+					$self->{value}.="DB\t"
+						.join(",",@str[0..15])."\n";
+					foreach (0..15) { shift @str; }
+				    }
+				    $self->{value}.="DB\t"
+						.join(",",@str) if (@str);
+				    last;
+				  };
+		/\.comm/    && do { my @str=split(/,\s*/,$$line);
+				    my $v=undef;
+				    if ($nasm) {
+					$v.="common	$prefix@str[0] @str[1]";
+				    } else {
+					$v="$current_segment\tENDS\n" if ($current_segment);
+					$current_segment = "_DATA";
+					$v.="$current_segment\tSEGMENT\n";
+					$v.="COMM	@str[0]:DWORD:".@str[1]/4;
+				    }
+				    $self->{value} = $v;
 				    last;
 				  };
 	    }
-	    $line = "";
+	    $$line = "";
 	}
 
 	$ret;
@@ -390,53 +683,263 @@ my $current_function;
     }
 }
 
-while($line=<>) {
+sub rex {
+ my $opcode=shift;
+ my ($dst,$src,$rex)=@_;
+
+   $rex|=0x04 if($dst>=8);
+   $rex|=0x01 if($src>=8);
+   push @$opcode,($rex|0x40) if ($rex);
+}
+
+# Upon initial x86_64 introduction SSE>2 extensions were not introduced
+# yet. In order not to be bothered by tracing exact assembler versions,
+# but at the same time to provide a bare security minimum of AES-NI, we
+# hard-code some instructions. Extensions past AES-NI on the other hand
+# are traced by examining assembler version in individual perlasm
+# modules...
+
+my %regrm = (	"%eax"=>0, "%ecx"=>1, "%edx"=>2, "%ebx"=>3,
+		"%esp"=>4, "%ebp"=>5, "%esi"=>6, "%edi"=>7	);
+
+my $movq = sub {	# elderly gas can't handle inter-register movq
+  my $arg = shift;
+  my @opcode=(0x66);
+    if ($arg =~ /%xmm([0-9]+),\s*%r(\w+)/) {
+	my ($src,$dst)=($1,$2);
+	if ($dst !~ /[0-9]+/)	{ $dst = $regrm{"%e$dst"}; }
+	rex(\@opcode,$src,$dst,0x8);
+	push @opcode,0x0f,0x7e;
+	push @opcode,0xc0|(($src&7)<<3)|($dst&7);	# ModR/M
+	@opcode;
+    } elsif ($arg =~ /%r(\w+),\s*%xmm([0-9]+)/) {
+	my ($src,$dst)=($2,$1);
+	if ($dst !~ /[0-9]+/)	{ $dst = $regrm{"%e$dst"}; }
+	rex(\@opcode,$src,$dst,0x8);
+	push @opcode,0x0f,0x6e;
+	push @opcode,0xc0|(($src&7)<<3)|($dst&7);	# ModR/M
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $pextrd = sub {
+    if (shift =~ /\$([0-9]+),\s*%xmm([0-9]+),\s*(%\w+)/) {
+      my @opcode=(0x66);
+	my $imm=$1;
+	my $src=$2;
+	my $dst=$3;
+	if ($dst =~ /%r([0-9]+)d/)	{ $dst = $1; }
+	elsif ($dst =~ /%e/)		{ $dst = $regrm{$dst}; }
+	rex(\@opcode,$src,$dst);
+	push @opcode,0x0f,0x3a,0x16;
+	push @opcode,0xc0|(($src&7)<<3)|($dst&7);	# ModR/M
+	push @opcode,$imm;
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $pinsrd = sub {
+    if (shift =~ /\$([0-9]+),\s*(%\w+),\s*%xmm([0-9]+)/) {
+      my @opcode=(0x66);
+	my $imm=$1;
+	my $src=$2;
+	my $dst=$3;
+	if ($src =~ /%r([0-9]+)/)	{ $src = $1; }
+	elsif ($src =~ /%e/)		{ $src = $regrm{$src}; }
+	rex(\@opcode,$dst,$src);
+	push @opcode,0x0f,0x3a,0x22;
+	push @opcode,0xc0|(($dst&7)<<3)|($src&7);	# ModR/M
+	push @opcode,$imm;
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $pshufb = sub {
+    if (shift =~ /%xmm([0-9]+),\s*%xmm([0-9]+)/) {
+      my @opcode=(0x66);
+	rex(\@opcode,$2,$1);
+	push @opcode,0x0f,0x38,0x00;
+	push @opcode,0xc0|($1&7)|(($2&7)<<3);		# ModR/M
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $palignr = sub {
+    if (shift =~ /\$([0-9]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
+      my @opcode=(0x66);
+	rex(\@opcode,$3,$2);
+	push @opcode,0x0f,0x3a,0x0f;
+	push @opcode,0xc0|($2&7)|(($3&7)<<3);		# ModR/M
+	push @opcode,$1;
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $pclmulqdq = sub {
+    if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
+      my @opcode=(0x66);
+	rex(\@opcode,$3,$2);
+	push @opcode,0x0f,0x3a,0x44;
+	push @opcode,0xc0|($2&7)|(($3&7)<<3);		# ModR/M
+	my $c=$1;
+	push @opcode,$c=~/^0/?oct($c):$c;
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $rdrand = sub {
+    if (shift =~ /%[er](\w+)/) {
+      my @opcode=();
+      my $dst=$1;
+	if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
+	rex(\@opcode,0,$1,8);
+	push @opcode,0x0f,0xc7,0xf0|($dst&7);
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $rdseed = sub {
+    if (shift =~ /%[er](\w+)/) {
+      my @opcode=();
+      my $dst=$1;
+	if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
+	rex(\@opcode,0,$1,8);
+	push @opcode,0x0f,0xc7,0xf8|($dst&7);
+	@opcode;
+    } else {
+	();
+    }
+};
+
+sub rxb {
+ my $opcode=shift;
+ my ($dst,$src1,$src2,$rxb)=@_;
+
+   $rxb|=0x7<<5;
+   $rxb&=~(0x04<<5) if($dst>=8);
+   $rxb&=~(0x01<<5) if($src1>=8);
+   $rxb&=~(0x02<<5) if($src2>=8);
+   push @$opcode,$rxb;
+}
+
+my $vprotd = sub {
+    if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
+      my @opcode=(0x8f);
+	rxb(\@opcode,$3,$2,-1,0x08);
+	push @opcode,0x78,0xc2;
+	push @opcode,0xc0|($2&7)|(($3&7)<<3);		# ModR/M
+	my $c=$1;
+	push @opcode,$c=~/^0/?oct($c):$c;
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $vprotq = sub {
+    if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
+      my @opcode=(0x8f);
+	rxb(\@opcode,$3,$2,-1,0x08);
+	push @opcode,0x78,0xc3;
+	push @opcode,0xc0|($2&7)|(($3&7)<<3);		# ModR/M
+	my $c=$1;
+	push @opcode,$c=~/^0/?oct($c):$c;
+	@opcode;
+    } else {
+	();
+    }
+};
+
+my $endbranch = sub {
+    (0xf3,0x0f,0x1e,0xfa);
+};
 
-    chomp($line);
+if ($nasm) {
+    print <<___;
+default	rel
+%define XMMWORD
+%define YMMWORD
+%define ZMMWORD
+___
+} elsif ($masm) {
+    print <<___;
+OPTION	DOTNAME
+___
+}
+while(defined(my $line=<>)) {
+
+    $line =~ s|\R$||;           # Better chomp
 
     $line =~ s|[#!].*$||;	# get rid of asm-style comments...
     $line =~ s|/\*.*\*/||;	# ... and C-style comments...
     $line =~ s|^\s+||;		# ... and skip white spaces in beginning
+    $line =~ s|\s+$||;		# ... and at the end
 
-    undef $label;
-    undef $opcode;
-    undef $dst;
-    undef $src;
-    undef $sz;
-
-    if ($label=label->re(\$line))	{ print $label->out(); }
+    if (my $label=label->re(\$line))	{ print $label->out(); }
 
-    if (directive->re(\$line)) {
-	printf "%s",directive->out();
-    } elsif ($opcode=opcode->re(\$line)) { ARGUMENT: {
+    if (my $directive=directive->re(\$line)) {
+	printf "%s",$directive->out();
+    } elsif (my $opcode=opcode->re(\$line)) {
+	my $asm = eval("\$".$opcode->mnemonic());
+	
+	if ((ref($asm) eq 'CODE') && scalar(my @bytes=&$asm($line))) {
+	    print $gas?".byte\t":"DB\t",join(',',@bytes),"\n";
+	    next;
+	}
 
-	if ($src=register->re(\$line))	{ opcode->size($src->size()); }
-	elsif ($src=const->re(\$line))	{ }
-	elsif ($src=ea->re(\$line))	{ }
-	elsif ($src=expr->re(\$line))	{ }
+	my @args;
+	ARGUMENT: while (1) {
+	    my $arg;
 
-	last ARGUMENT if ($line !~ /^,/);
+	    ($arg=register->re(\$line, $opcode))||
+	    ($arg=const->re(\$line))		||
+	    ($arg=ea->re(\$line, $opcode))	||
+	    ($arg=expr->re(\$line, $opcode))	||
+	    last ARGUMENT;
 
-	$line = substr($line,1); $line =~ s/^\s+//;
+	    push @args,$arg;
 
-	if ($dst=register->re(\$line))	{ opcode->size($dst->size()); }
-	elsif ($dst=const->re(\$line))	{ }
-	elsif ($dst=ea->re(\$line))	{ }
+	    last ARGUMENT if ($line !~ /^,/);
 
+	    $line =~ s/^,\s*//;
 	} # ARGUMENT:
 
-	$sz=opcode->size();
+	if ($#args>=0) {
+	    my $insn;
+	    my $sz=$opcode->size();
 
-	if (defined($dst)) {
-	    if (!$masm) {
-		printf "\t%s\t%s,%s",	$opcode->out($dst->size()),
-					$src->out($sz),$dst->out($sz);
+	    if ($gas) {
+		$insn = $opcode->out($#args>=1?$args[$#args]->size():$sz);
+		@args = map($_->out($sz),@args);
+		printf "\t%s\t%s",$insn,join(",",@args);
 	    } else {
-		printf "\t%s\t%s,%s",	$opcode->out(),
-					$dst->out($sz),$src->out($sz);
+		$insn = $opcode->out();
+		foreach (@args) {
+		    my $arg = $_->out();
+		    # $insn.=$sz compensates for movq, pinsrw, ...
+		    if ($arg =~ /^xmm[0-9]+$/) { $insn.=$sz; $sz="x" if(!$sz); last; }
+		    if ($arg =~ /^ymm[0-9]+$/) { $insn.=$sz; $sz="y" if(!$sz); last; }
+		    if ($arg =~ /^zmm[0-9]+$/) { $insn.=$sz; $sz="z" if(!$sz); last; }
+		    if ($arg =~ /^mm[0-9]+$/)  { $insn.=$sz; $sz="q" if(!$sz); last; }
+		}
+		@args = reverse(@args);
+		undef $sz if ($nasm && $opcode->mnemonic() eq "lea");
+		printf "\t%s\t%s",$insn,join(",",map($_->out($sz),@args));
 	    }
-	} elsif (defined($src)) {
-	    printf "\t%s\t%s",$opcode->out(),$src->out($sz);
 	} else {
 	    printf "\t%s",$opcode->out();
 	}
@@ -445,11 +948,12 @@ while($line=<>) {
     print $line,"\n";
 }
 
-print "\n$current_segment\tENDS\nEND\n" if ($masm);
+print "\n$current_segment\tENDS\n"	if ($current_segment && $masm);
+print "END\n"				if ($masm);
 
 close STDOUT;
 
-#################################################
+#################################################
 # Cross-reference x86_64 ABI "card"
 #
 # 		Unix		Win64
@@ -475,7 +979,7 @@ close STDOUT;
 # (#)	Nth argument, volatile
 #
 # In Unix terms top of stack is argument transfer area for arguments
-# which could not be accomodated in registers. Or in other words 7th
+# which could not be accommodated in registers. Or in other words 7th
 # [integer] argument resides at 8(%rsp) upon function entry point.
 # 128 bytes above %rsp constitute a "red zone" which is not touched
 # by signal handlers and can be used as temporal storage without
@@ -513,3 +1017,161 @@ close STDOUT;
 #	movq	16(%rsp),%rsi
 # endif
 #	ret
+#
+#################################################
+# Win64 SEH, Structured Exception Handling.
+#
+# Unlike on Unix systems(*) lack of Win64 stack unwinding information
+# has undesired side-effect at run-time: if an exception is raised in
+# assembler subroutine such as those in question (basically we're
+# referring to segmentation violations caused by malformed input
+# parameters), the application is briskly terminated without invoking
+# any exception handlers, most notably without generating memory dump
+# or any user notification whatsoever. This poses a problem. It's
+# possible to address it by registering custom language-specific
+# handler that would restore processor context to the state at
+# subroutine entry point and return "exception is not handled, keep
+# unwinding" code. Writing such handler can be a challenge... But it's
+# doable, though requires certain coding convention. Consider following
+# snippet:
+#
+# .type	function,@function
+# function:
+#	movq	%rsp,%rax	# copy rsp to volatile register
+#	pushq	%r15		# save non-volatile registers
+#	pushq	%rbx
+#	pushq	%rbp
+#	movq	%rsp,%r11
+#	subq	%rdi,%r11	# prepare [variable] stack frame
+#	andq	$-64,%r11
+#	movq	%rax,0(%r11)	# check for exceptions
+#	movq	%r11,%rsp	# allocate [variable] stack frame
+#	movq	%rax,0(%rsp)	# save original rsp value
+# magic_point:
+#	...
+#	movq	0(%rsp),%rcx	# pull original rsp value
+#	movq	-24(%rcx),%rbp	# restore non-volatile registers
+#	movq	-16(%rcx),%rbx
+#	movq	-8(%rcx),%r15
+#	movq	%rcx,%rsp	# restore original rsp
+#	ret
+# .size function,.-function
+#
+# The key is that up to magic_point copy of original rsp value remains
+# in chosen volatile register and no non-volatile register, except for
+# rsp, is modified. While past magic_point rsp remains constant till
+# the very end of the function. In this case custom language-specific
+# exception handler would look like this:
+#
+# EXCEPTION_DISPOSITION handler (EXCEPTION_RECORD *rec,ULONG64 frame,
+#		CONTEXT *context,DISPATCHER_CONTEXT *disp)
+# {	ULONG64 *rsp = (ULONG64 *)context->Rax;
+#	if (context->Rip >= magic_point)
+#	{   rsp = ((ULONG64 **)context->Rsp)[0];
+#	    context->Rbp = rsp[-3];
+#	    context->Rbx = rsp[-2];
+#	    context->R15 = rsp[-1];
+#	}
+#	context->Rsp = (ULONG64)rsp;
+#	context->Rdi = rsp[1];
+#	context->Rsi = rsp[2];
+#
+#	memcpy (disp->ContextRecord,context,sizeof(CONTEXT));
+#	RtlVirtualUnwind(UNW_FLAG_NHANDLER,disp->ImageBase,
+#		dips->ControlPc,disp->FunctionEntry,disp->ContextRecord,
+#		&disp->HandlerData,&disp->EstablisherFrame,NULL);
+#	return ExceptionContinueSearch;
+# }
+#
+# It's appropriate to implement this handler in assembler, directly in
+# function's module. In order to do that one has to know members'
+# offsets in CONTEXT and DISPATCHER_CONTEXT structures and some constant
+# values. Here they are:
+#
+#	CONTEXT.Rax				120
+#	CONTEXT.Rcx				128
+#	CONTEXT.Rdx				136
+#	CONTEXT.Rbx				144
+#	CONTEXT.Rsp				152
+#	CONTEXT.Rbp				160
+#	CONTEXT.Rsi				168
+#	CONTEXT.Rdi				176
+#	CONTEXT.R8				184
+#	CONTEXT.R9				192
+#	CONTEXT.R10				200
+#	CONTEXT.R11				208
+#	CONTEXT.R12				216
+#	CONTEXT.R13				224
+#	CONTEXT.R14				232
+#	CONTEXT.R15				240
+#	CONTEXT.Rip				248
+#	CONTEXT.Xmm6				512
+#	sizeof(CONTEXT)				1232
+#	DISPATCHER_CONTEXT.ControlPc		0
+#	DISPATCHER_CONTEXT.ImageBase		8
+#	DISPATCHER_CONTEXT.FunctionEntry	16
+#	DISPATCHER_CONTEXT.EstablisherFrame	24
+#	DISPATCHER_CONTEXT.TargetIp		32
+#	DISPATCHER_CONTEXT.ContextRecord	40
+#	DISPATCHER_CONTEXT.LanguageHandler	48
+#	DISPATCHER_CONTEXT.HandlerData		56
+#	UNW_FLAG_NHANDLER			0
+#	ExceptionContinueSearch			1
+#
+# In order to tie the handler to the function one has to compose
+# couple of structures: one for .xdata segment and one for .pdata.
+#
+# UNWIND_INFO structure for .xdata segment would be
+#
+# function_unwind_info:
+#	.byte	9,0,0,0
+#	.rva	handler
+#
+# This structure designates exception handler for a function with
+# zero-length prologue, no stack frame or frame register.
+#
+# To facilitate composing of .pdata structures, auto-generated "gear"
+# prologue copies rsp value to rax and denotes next instruction with
+# .LSEH_begin_{function_name} label. This essentially defines the SEH
+# styling rule mentioned in the beginning. Position of this label is
+# chosen in such manner that possible exceptions raised in the "gear"
+# prologue would be accounted to caller and unwound from latter's frame.
+# End of function is marked with respective .LSEH_end_{function_name}
+# label. To summarize, .pdata segment would contain
+#
+#	.rva	.LSEH_begin_function
+#	.rva	.LSEH_end_function
+#	.rva	function_unwind_info
+#
+# Reference to function_unwind_info from .xdata segment is the anchor.
+# In case you wonder why references are 32-bit .rvas and not 64-bit
+# .quads. References put into these two segments are required to be
+# *relative* to the base address of the current binary module, a.k.a.
+# image base. No Win64 module, be it .exe or .dll, can be larger than
+# 2GB and thus such relative references can be and are accommodated in
+# 32 bits.
+#
+# Having reviewed the example function code, one can argue that "movq
+# %rsp,%rax" above is redundant. It is not! Keep in mind that on Unix
+# rax would contain an undefined value. If this "offends" you, use
+# another register and refrain from modifying rax till magic_point is
+# reached, i.e. as if it was a non-volatile register. If more registers
+# are required prior [variable] frame setup is completed, note that
+# nobody says that you can have only one "magic point." You can
+# "liberate" non-volatile registers by denoting last stack off-load
+# instruction and reflecting it in finer grade unwind logic in handler.
+# After all, isn't it why it's called *language-specific* handler...
+#
+# Attentive reader can notice that exceptions would be mishandled in
+# auto-generated "gear" epilogue. Well, exception effectively can't
+# occur there, because if memory area used by it was subject to
+# segmentation violation, then it would be raised upon call to the
+# function (and as already mentioned be accounted to caller, which is
+# not a problem). If you're still not comfortable, then define tail
+# "magic point" just prior ret instruction and have handler treat it...
+#
+# (*)	Note that we're talking about run-time, not debug-time. Lack of
+#	unwind information makes debugging hard on both Windows and
+#	Unix. "Unlike" referes to the fact that on Unix signal handler
+#	will always be invoked, core dumped and appropriate exit code
+#	returned to parent (for user notification).