Cim*_*ali 10 c assembly intel performancecounter cpu-registers
我想在XeonE5 Sandy Bridge上使用基于精确事件的采样(PEBS)来记录特定事件的所有地址(例如缓存未命中).
但是,Core TM i7处理器和Intel®XeonTM5500处理器性能分析指南(第24页)包含以下警告:
由于PEBS机制在指令完成时捕获寄存器的值,因此无法重建以下类型的加载指令(Intel asm约定)的解除引用的地址.
MOV RAX, [RAX+const]
这种指令主要与指针追逐相关联.
mystruc = mystruc->next;
这是捕获存储器指令地址的这种方法的重大缺点.
根据objdump,我在程序中有许多该表单的加载指令.有什么办法可以避免吗？
由于这是一个特定于英特尔的问题,解决方案不必以任何方式移植,它只需要工作.我的代码是用C语言编写的,我理想地寻找编译器级解决方案(gcc或icc),但欢迎任何建议.
一些例子:
mov 0x18(%rdi),%rdi
mov (%rcx,%rax,8),%rax
在这两种情况下,该指令退役之后(因此当我看到的寄存器值来找出我装到/从)的地址(分别的值%rdi + 18和%rcx + 8 * %rax这些实施例中)通过的结果重写mov.
您想要做的是转换表单的所有指令：
mov (%rcx,%rax,8),%rax
进入：
mov (%rcx,%rax,8),%r11
mov %r11,%rax
通过修改编译器生成的汇编源代码，可以更轻松地完成此操作。下面是一个perl脚本，它将通过读取和修改.s文件来执行所有必要的转换。
只需更改构建以生成.s文件而不是.o文件，应用脚本，然后.o使用as或生成gcc
这是实际的脚本。我已经按照下面评论中的构建过程在我自己的一些来源上对其进行了测试。
该脚本具有以下特点：
%r11在尝试使用被调用者保存的寄存器之前尝试使用未使用的临时寄存器（例如或未使用的参数寄存器）push到函数序言和pop函数 [多个]ret语句.s文件#!/usr/bin/perl
# pebsfix/pebsfixup -- fix assembler source for PEBS usage
#
# command line options:
# "-a" -- use only full 64 bit targets
# "-l" -- do _not_ use lea
# "-D[diff-file]" -- show differences (default output: "./DIFF")
# "-n10" -- do _not_ use register %r10 for temporary (default is use it)
# "-o" -- overwrite input files (can be multiple)
# "-O<outfile>" -- output file (only one .s input allowed)
# "-q" -- suppress warnings
# "-T[lvl]" -- debug trace
#
# "-o" and "-O" are mutually exclusive
#
# command line script test options:
# "-N[TPA]" -- disable temp register types [for testing]
# "-P" -- force push/pop on all functions
#
# command line arguments:
# 1-- list of .s files to process [or directory to search]
# for a given file "foo.s", output is to "foo.TMP"
# if (-o is given, "foo.TMP" is renamed to "foo.s")
#
# suggested usage:
# change build to produce .s files
# FROM:
# cc [options] -c foo.c
# TO:
# cc [options] -c -S foo.c
# pebsfixup -o foo.s
# cc -c foo.s
#
# suggested compiler options:
# [probably only really needed if push/pop required. use -NP to verify]
# (1) use either of
# -O2 -fno-optimize-sibling-calls
# -O1
# (2) use -mno-omit-leaf-frame-pointer
# (3) use -mno-red-zone [probably not required in any case]
#
# NOTES:
# (1) red zones are only really useful for leaf functions (i.e. if fncA calls
# fncB, fncA's red zone would be clobbered)
# (2) pushing onto the stack isn't a problem if there is a formal stack frame
# (3) the push is okay if the function has no more than six arguments (i.e.
# does _not_ use positive offsets from %rsp to access them)
#pragma pgmlns
use strict qw(vars subs);
our $pgmtail;
our $opt_a;
our $opt_T;
our $opt_D;
our $opt_l;
our $opt_n10;
our $opt_N;
our $opt_P;
our $opt_q;
our $opt_o;
our $opt_O;
our $opt_s;
our @reguse;
our %reguse_tobase;
our %reguse_isbase;
our $regusergx;
our @regtmplist;
our %regtmp_type;
our $diff;
our $sepflg;
our $fatal;
our @cmtprt;
master(@ARGV);
exit(0);
# master -- master control
sub master
{
my(@argv) = @_;
my($xfsrc);
my($file,@files);
my($bf);
$pgmtail = "pebsfixup";
optget(\@argv);
# define all known/usable registers
regusejoin();
# define all registers that we may use as a temporary
regtmpall();
if (defined($opt_D)) {
unlink($opt_D);
}
# show usage
if (@argv <= 0) {
$file = $0;
open($xfsrc,"<$file") ||
sysfault("$pgmtail: unable to open '%s' -- $!\n",$file);
while ($bf = <$xfsrc>) {
chomp($bf);
next if ($bf =~ /^#!/);
last unless ($bf =~ s/^#//);
$bf =~ s/^# ?//;
print($bf,"\n");
}
close($xfsrc);
exit(1);
}
foreach $file (@argv) {
if (-d $file) {
dodir(\@files,$file);
}
else {
push(@files,$file);
}
}
if (defined($opt_O)) {
sysfault("$pgmtail: -O may have only one input file\n")
if (@files != 1);
sysfault("$pgmtail: -O and -o are mutually exclusive\n")
if ($opt_o);
}
foreach $file (@files) {
dofile($file);
}
if (defined($opt_D)) {
exec("less",$opt_D);
}
}
# dodir -- process directory
sub dodir
{
my($files,$dir) = @_;
my($file,@files);
@files = (`find $dir -type f -name '*.s'`);
foreach $file (@files) {
chomp($file);
push(@$files,$file);
}
}
# dofile -- process file
sub dofile
{
my($file) = @_;
my($ofile);
my($xfsrc);
my($xfdst);
my($bf,$lno,$outoff);
my($fixoff);
my($lhs,$rhs);
my($xop,$arg);
my($ix);
my($sym,$val,$typ);
my(%sym_type);
my($fnc,$fnx,%fnx_lookup,@fnxlist);
my($retlist);
my($uselook,@uselist,%avail);
my($fixreg,$fixrtyp);
my($sixlist);
my($fix,$fixlist);
my($fixtot);
my(@fix);
my(@outlist);
my($relaxflg);
my($cmtchr);
undef($fatal);
undef(@cmtprt);
msgprt("\n")
if ($sepflg);
$sepflg = 1;
msgprt("$pgmtail: processing %s ...\n",$file);
$cmtchr = "#";
cmtprt("%s\n","-" x 78);
cmtprt("FILE: %s\n",$file);
# get the output file
$ofile = $file;
sysfault("$pgmtail: bad suffix -- file='%s'\n",$file)
unless ($ofile =~ s/[.]s$//);
$ofile .= ".TMP";
# use explicit output file
if (defined($opt_O)) {
$ofile = $opt_O;
sysfault("$pgmtail: output file may not be input file -- use -o instead\n")
if ($ofile eq $file);
}
open($xfsrc,"<$file") ||
sysfault("$pgmtail: unable to open '%s' -- $!\n",$file);
$lno = 0;
while ($bf = <$xfsrc>) {
chomp($bf);
$bf =~ s/\s+$//;
$outoff = $lno;
++$lno;
push(@outlist,$bf);
# clang adds comments
$ix = index($bf,"#");
if ($ix >= 0) {
$bf = substr($bf,0,$ix);
$bf =~ s/\s+$//;
}
# look for ".type blah, @function"
# NOTE: this always comes before the actual label line [we hope ;-)]
if ($bf =~ /^\s+[.]type\s+([^,]+),\s*(\S+)/) {
($sym,$val) = ($1,$2);
$val =~ s/^\@//;
$sym_type{$sym} = $val;
cmtprt("\n");
cmtprt("TYPE: %s --> %s\n",$sym,$val);
next;
}
# look for "label:"
if ($bf =~ /^([a-z_A-Z][a-z_A-Z0-9]*):$/) {
$sym = $1;
next if ($sym_type{$sym} ne "function");
$fnc = $sym;
cmtprt("FUNCTION: %s\n",$fnc);
$fnx = {};
$fnx_lookup{$sym} = $fnx;
push(@fnxlist,$fnx);
$fnx->{fnx_fnc} = $fnc;
$fnx->{fnx_outoff} = $outoff;
$uselook = {};
$fnx->{fnx_used} = $uselook;
$retlist = [];
$fnx->{fnx_retlist} = $retlist;
$fixlist = [];
$fnx->{fnx_fixlist} = $fixlist;
$sixlist = [];
$fnx->{fnx_sixlist} = $sixlist;
next;
}
# remember all registers used by function:
while ($bf =~ /($regusergx)/gpo) {
$sym = ${^MATCH};
$val = $reguse_tobase{$sym};
dbgprt(3,"dofile: REGUSE sym='%s' val='%s'\n",$sym,$val);
$uselook->{$sym} += 1;
$uselook->{$val} += 1
if ($val ne $sym);
}
# handle returns
if ($bf =~ /^\s+ret/) {
push(@$retlist,$outoff);
next;
}
if ($bf =~ /^\s+rep[a-z]*\s+ret/) {
push(@$retlist,$outoff);
next;
}
# split up "movq 16(%rax),%rax" ...
$ix = rindex($bf,",");
next if ($ix < 0);
# ... into "movq 16(%rax)"
$lhs = substr($bf,0,$ix);
$lhs =~ s/\s+$//;
# check for "movq 16(%rsp)" -- this means that the function has/uses
# more than six arguments (i.e. we may _not_ push/pop because it
# wreaks havoc with positive offsets)
# FIXME/CAE -- we'd have to adjust them by 8 which we don't do
(undef,$rhs) = split(" ",$lhs);
if ($rhs =~ /^(\d+)[(]%rsp[)]$/) {
push(@$sixlist,$outoff);
cmtprt("SIXARG: %s (line %d)\n",$rhs,$lno);
}
# ... and "%rax"
$rhs = substr($bf,$ix + 1);
$rhs =~ s/^\s+//;
# target must be a [simple] register [or source scan will blow up]
# (e.g. we actually had "cmp %ebp,(%rax,%r14)")
next if ($rhs =~ /[)]/);
# ensure we have the "%" prefix
next unless ($rhs =~ /^%/);
# we only want the full 64 bit reg as target
# (e.g. "mov (%rbx),%al" doesn't count)
$val = $reguse_tobase{$rhs};
if ($opt_a) {
next if ($val ne $rhs);
}
else {
next unless (defined($val));
}
# source operand must contain target [base] register
next unless ($lhs =~ /$val/);
###cmtprt("1: %s,%s\n",$lhs,$rhs);
# source operand must be of the "right" type
# FIXME/CAE -- we may need to revise this
next unless ($lhs =~ /[(]/);
cmtprt("NEEDFIX: %s,%s (line %d)\n",$lhs,$rhs,$lno);
# remember the place we need to fix for later
$fix = {};
push(@$fixlist,$fix);
$fix->{fix_outoff} = $outoff;
$fix->{fix_lhs} = $lhs;
$fix->{fix_rhs} = $rhs;
}
close($xfsrc);
# get total number of fixups
foreach $fnx (@fnxlist) {
$fixlist = $fnx->{fnx_fixlist};
$fixtot += @$fixlist;
}
msgprt("$pgmtail: needs %d fixups\n",$fixtot)
if ($fixtot > 0);
# fix each function
foreach $fnx (@fnxlist) {
cmtprt("\n");
cmtprt("FNC: %s\n",$fnx->{fnx_fnc});
$fixlist = $fnx->{fnx_fixlist};
# get the fixup register
($fixreg,$fixrtyp) = regtmploc($fnx,$fixlist);
# show number of return points
{
$retlist = $fnx->{fnx_retlist};
cmtprt(" RET: %d\n",scalar(@$retlist));
last if (@$retlist >= 1);
# NOTE: we display this warning because we may not be able to
# handle all situations
$relaxflg = (@$fixlist <= 0) || ($fixrtyp ne "P");
last if ($relaxflg && $opt_q);
errprt("$pgmtail: in file '%s'\n",$file);
errprt("$pgmtail: function '%s' has no return points\n",
$fnx->{fnx_fnc});
errprt("$pgmtail: suggest recompile with correct options\n");
if (@$fixlist <= 0) {
errprt("$pgmtail: working around because function needs no fixups\n");
last;
}
if ($fixrtyp ne "P") {
errprt("$pgmtail: working around because fixup reg does not need to be saved\n");
last;
}
}
# show stats on register usage in function
$uselook = $fnx->{fnx_used};
@uselist = sort(keys(%$uselook));
cmtprt(" USED:\n");
%avail = %reguse_isbase;
foreach $sym (@uselist) {
$val = $uselook->{$sym};
$typ = $regtmp_type{$sym};
$typ = sprintf(" (TYPE: %s)",$typ)
if (defined($typ));
cmtprt(" %s used %d%s\n",$sym,$val,$typ);
$val = $reguse_tobase{$sym};
delete($avail{$val});
}
# show function's available [unused] registers
@uselist = keys(%avail);
@uselist = sort(regusesort @uselist);
if (@uselist > 0) {
cmtprt(" AVAIL:\n");
foreach $sym (@uselist) {
$typ = $regtmp_type{$sym};
$typ = sprintf(" (TYPE: %s)",$typ)
if (defined($typ));
cmtprt(" %s%s\n",$sym,$typ);
}
}
# skip over any functions that don't need fixing _and_ have a temp
# register
if (@$fixlist <= 0 && (! $opt_P)) {
next if (defined($fixreg));
}
msgprt("$pgmtail: function %s\n",$fnx->{fnx_fnc});
# skip function because we don't have a fixup register but report it
# here
unless (defined($fixreg)) {
$bf = (@$fixlist > 0) ? "FATAL" : "can be ignored -- no fixups needed";
msgprt("$pgmtail: FIXNOREG (%s)\n",$bf);
cmtprt(" FIXNOREG (%s)\n",$bf);
next;
}
msgprt("$pgmtail: FIXREG --> %s (TYPE: %s)\n",$fixreg,$fixrtyp);
cmtprt(" FIXREG --> %s (TYPE: %s)\n",$fixreg,$fixrtyp);
foreach $fix (@$fixlist) {
$outoff = $fix->{fix_outoff};
undef(@fix);
cmtprt(" FIXOLD %s\n",$outlist[$outoff]);
# original
if ($opt_l) {
$bf = sprintf("%s,%s",$fix->{fix_lhs},$fixreg);
push(@fix,$bf);
$bf = sprintf("\tmov\t%s,%s",$fixreg,$fix->{fix_rhs});
push(@fix,$bf);
}
# use lea
else {
($xop,$arg) = split(" ",$fix->{fix_lhs});
$bf = sprintf("\tlea\t\t%s,%s",$arg,$fixreg);
push(@fix,$bf);
$bf = sprintf("\t%s\t(%s),%s",$xop,$fixreg,$fix->{fix_rhs});
push(@fix,$bf);
}
foreach $bf (@fix) {
cmtprt(" FIXNEW %s\n",$bf);
}
$outlist[$outoff] = [@fix];
}
unless ($opt_P) {
next if ($fixrtyp ne "P");
}
# fix the function prolog
$outoff = $fnx->{fnx_outoff};
$lhs = $outlist[$outoff];
$rhs = sprintf("\tpush\t%s",$fixreg);
$bf = [$lhs,$rhs,""];
$outlist[$outoff] = $bf;
# fix the function return points
$retlist = $fnx->{fnx_retlist};
foreach $outoff (@$retlist) {
$rhs = $outlist[$outoff];
$lhs = sprintf("\tpop\t%s",$fixreg);
$bf = ["",$lhs,$rhs];
$outlist[$outoff] = $bf;
}
}
open($xfdst,">$ofile") ||
sysfault("$pgmtail: unable to open '%s' -- $!\n",$ofile);
# output all the assembler text
foreach $bf (@outlist) {
# ordinary line
unless (ref($bf)) {
print($xfdst $bf,"\n");
next;
}
# apply a fixup
foreach $rhs (@$bf) {
print($xfdst $rhs,"\n");
}
}
# output all our reasoning as comments at the bottom
foreach $bf (@cmtprt) {
if ($bf eq "") {
print($xfdst $cmtchr,$bf,"\n");
}
else {
print($xfdst $cmtchr," ",$bf,"\n");
}
}
close($xfdst);
# get difference
if (defined($opt_D)) {
system("diff -u $file $ofile >> $opt_D");
}
# install fixed/modified file
{
last unless ($opt_o || defined($opt_O));
last if ($fatal);
msgprt("$pgmtail: installing ...\n");
rename($ofile,$file);
}
}
# regtmpall -- define all temporary register candidates
sub regtmpall
{
dbgprt(1,"regtmpall: ENTER\n");
regtmpdef("%r11","T");
# NOTES:
# (1) see notes on %r10 in ABI at bottom -- should we use it?
# (2) a web search on "shared chain" and "x86" only produces 28 results
# (3) some gcc code uses it as an ordinary register
# (4) so, use it unless told not to
regtmpdef("%r10","T")
unless ($opt_n10);
# argument registers (a6-a1)
regtmpdef("%r9","A6");
regtmpdef("%r8","A5");
regtmpdef("%rcx","A4");
regtmpdef("%rdx","A3");
regtmpdef("%rsi","A2");
regtmpdef("%rdi","A1");
# callee preserved registers
regtmpdef("%r15","P");
regtmpdef("%r14","P");
regtmpdef("%r13","P");
regtmpdef("%r12","P");
dbgprt(1,"regtmpall: EXIT\n");
}
# regtmpdef -- define usable temp registers
sub regtmpdef
{
my($sym,$typ) = @_;
dbgprt(1,"regtmpdef: SYM sym='%s' typ='%s'\n",$sym,$typ);
push(@regtmplist,$sym);
$regtmp_type{$sym} = $typ;
}
# regtmploc -- locate temp register to fix problem
sub regtmploc
{
my($fnx,$fixlist) = @_;
my($sixlist);
my($uselook);
my($regrhs);
my($fixcnt);
my($coretyp);
my($reglhs,$regtyp);
dbgprt(2,"regtmploc: ENTER fnx_fnc='%s'\n",$fnx->{fnx_fnc});
$sixlist = $fnx->{fnx_sixlist};
$fixcnt = @$fixlist;
$fixcnt = 1
if ($opt_P);
$uselook = $fnx->{fnx_used};
foreach $regrhs (@regtmplist) {
dbgprt(2,"regtmploc: TRYREG regrhs='%s' uselook=%d\n",
$regrhs,$uselook->{$regrhs});
unless ($uselook->{$regrhs}) {
$regtyp = $regtmp_type{$regrhs};
$coretyp = $regtyp;
$coretyp =~ s/\d+$//;
# function uses stack arguments -- we can't push/pop
if (($coretyp eq "P") && (@$sixlist > 0)) {
dbgprt(2,"regtmploc: SIXREJ\n");
next;
}
if (defined($opt_N)) {
dbgprt(2,"regtmploc: TRYREJ opt_N='%s' regtyp='%s'\n",
$opt_N,$regtyp);
next if ($opt_N =~ /$coretyp/);
}
$reglhs = $regrhs;
last;
}
}
{
last if (defined($reglhs));
errprt("regtmploc: unable to locate usable fixup register for function '%s'\n",
$fnx->{fnx_fnc});
last if ($fixcnt <= 0);
$fatal = 1;
}
dbgprt(2,"regtmploc: EXIT reglhs='%s' regtyp='%s'\n",$reglhs,$regtyp);
($reglhs,$regtyp);
}
# regusejoin -- get regex for all registers
sub regusejoin
{
my($reg);
dbgprt(1,"regusejoin: ENTER\n");
# rax
foreach $reg (qw(a b c d)) {
regusedef($reg,"r_x","e_x","_l","_h");
}
# rdi/rsi
foreach $reg (qw(d s)) {
regusedef($reg,"r_i","e_i","_i","_il");
}
# rsp/rbp
foreach $reg (qw(b s)) {
regusedef($reg,"r_p","e_p");
}
foreach $reg (8,9,10,11,12,13,14,15) {
regusedef($reg,"r_","r_d","r_w","r_b");
}
$regusergx = join("|",reverse(sort(@reguse)));
dbgprt(1,"regusejoin: EXIT regusergx='%s'\n",$regusergx);
}
# regusedef -- define all registers
sub regusedef
{
my(@argv) = @_;
my($mid);
my($pat);
my($base);
$mid = shift(@argv);
dbgprt(1,"regusedef: ENTER mid='%s'\n",$mid);
foreach $pat (@argv) {
$pat = "%" . $pat;
$pat =~ s/_/$mid/;
$base //= $pat;
dbgprt(1,"regusedef: PAT pat='%s' base='%s'\n",$pat,$base);
push(@reguse,$pat);
$reguse_tobase{$pat} = $base;
}
$reguse_isbase{$base} = 1;
dbgprt(1,"regusedef: EXIT\n");
}
# regusesort -- sort base register names
sub regusesort
{
my($symlhs,$numlhs);
my($symrhs,$numrhs);
my($cmpflg);
{
($symlhs,$numlhs) = _regusesort($a);
($symrhs,$numrhs) = _regusesort($b);
$cmpflg = $symlhs cmp $symrhs;
last if ($cmpflg);
$cmpflg = $numlhs <=> $numrhs;
}
$cmpflg;
}
# _regusesort -- split up base register name
sub _regusesort
{
my($sym) = @_;
my($num);
if ($sym =~ s/(\d+)$//) {
$num = $1;
$num += 0;
$sym =~ s/[^%]/z/g;
}
($sym,$num);
}
# optget -- get options
sub optget
{
my($argv) = @_;
my($bf);
my($sym,$val);
my($dft,%dft);
foreach $sym (qw(a l n10 P q o s T)) {
$dft{$sym} = 1;
}
$dft{"N"} = "T";
$dft{"D"} = "DIFF";
while (1) {
$bf = $argv->[0];
$sym = $bf;
last unless ($sym =~ s/^-//);
last if ($sym eq "-");
shift(@$argv);
{
if ($sym =~ /([^=]+)=(.+)$/) {
($sym,$val) = ($1,$2);
last;
}