Date: Sun, 25 Nov 2007 13:54:22 -0800 (PST) From: Luoqi Chen <luoqi@luoqi.homeunix.org> To: current@freebsd.org Subject: gprof's broken in 7-CURRENT Message-ID: <200711252154.lAPLsMXb003966@luoqi.homeunix.org>
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Has anyone else noticed that gprof no longer works with gcc 4.2
compiled code? It has something to do with forced stack alignment.
Here's the cc -O -S output of this piece of code:
int main(int argc, char **argv)
{
if (argc < 2)
exit(1);
}
.globl main
.type main, @function
main:
leal 4(%esp), %ecx
andl $-16, %esp
pushl -4(%ecx)
pushl %ebp
movl %esp, %ebp
subl $56, %esp
movl %ecx, -16(%ebp)
movl %ebx, -12(%ebp)
movl %esi, -8(%ebp)
movl %edi, -4(%ebp)
call .mcount
movl 4(%ecx), %edi
cmpl $2, (%ecx)
jg .L83
movl $1, (%esp)
call exit
.p2align 4,,7
.L83:
Register %ecx becomes the new ap after the forced stack alignment,
however it is not preserved by .mcount. We can work around this
problem by preserving ecx in mcount, but a better solution would
be to fix gcc instead.
-lq
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