On 5/8/05, Steven Bosscher <[EMAIL PROTECTED]> wrote:
> Hi,
Hello,
> I have looked at the GCSE CPROP passes with CSE path following
> disabled ("-O1 -fgcse --param max-cse-path-length=1"). The input
> code are the cc1-i files from 20040726 (with checking enabled).
While that discussion flies way above my head, it seems to be about
gcse and i have enough grievance about it to jump in.
I've just pinged PR19680 (because it's still there) and just for the
sake of it i've tried the newly reported PR21463 with -fno-gcse and
it's quite interesting.
as reported, with gcse:
0000000000400610 <foo_t<float>::bar_ref(float, float)>:
400610: ucomiss 0x4(%rdi),%xmm1
400614: lea 0x4(%rdi),%rax
400618: lea 0xfffffffffffffff8(%rsp),%rdx
40061d: movss %xmm0,0xfffffffffffffffc(%rsp)
400623: movss %xmm1,0xfffffffffffffff8(%rsp)
400629: movaps %xmm1,%xmm2
40062c: cmova %rdx,%rax
400630: movss (%rax),%xmm1
400634: ucomiss %xmm1,%xmm0
400637: ja 400641 <foo_t<float>::bar_ref(float, float)+0x31>
400639: lea 0xfffffffffffffffc(%rsp),%rax
40063e: movaps %xmm0,%xmm1
400641: ucomiss (%rdi),%xmm2
400644: cmova %rdi,%rdx
400648: movss (%rdx),%xmm0
40064c: ucomiss %xmm0,%xmm1
40064f: jbe 400655 <foo_t<float>::bar_ref(float, float)+0x45>
400651: movss (%rax),%xmm0
400655: repz retq
without:
0000000000400610 <foo_t<float>::bar_ref(float, float)>:
400610: movss %xmm0,0xfffffffffffffffc(%rsp)
400616: lea 0xfffffffffffffff8(%rsp),%rcx
40061b: lea 0x4(%rdi),%rax
40061f: movss %xmm1,0xfffffffffffffff8(%rsp)
400625: lea 0xfffffffffffffffc(%rsp),%rdx
40062a: ucomiss 0x4(%rdi),%xmm1
40062e: cmova %rcx,%rax
400632: ucomiss (%rax),%xmm0
400635: cmovbe %rdx,%rax
400639: ucomiss (%rdi),%xmm1
40063c: movss (%rax),%xmm0
400640: cmovbe %rcx,%rdi
400644: ucomiss (%rdi),%xmm0
400647: cmova %rax,%rdi
40064b: movss (%rdi),%xmm0
40064f: retq
Again, sorry for hijacking that thread, but gcse is a convenient
scapegoat for most of my performance/codegen problems and i'd like to
know if there's mid-term hope.
Regards,
Thierry.
