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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@27786 91177308-0d34-0410-b5e6-96231b3b80d8
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Evan Cheng
2006-04-18 01:22:57 +00:00
parent 309db81c10
commit 74e955d931
1 changed files with 35 additions and 0 deletions
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35
lib/Target/X86/README.txt
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@@ -961,3 +961,38 @@ selector should select pshufd or The register allocator can made the two-address
to three-address transformation. to three-address transformation.
It also exposes some other problems. See MOV32ri -3 and the spills. It also exposes some other problems. See MOV32ri -3 and the spills.
//===---------------------------------------------------------------------===//
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25500
LLVM is producing bad code.
LBB_main_4: # cond_true44
addps %xmm1, %xmm2
subps %xmm3, %xmm2
movaps (%ecx), %xmm4
movaps %xmm2, %xmm1
addps %xmm4, %xmm1
addl $16, %ecx
incl %edx
cmpl $262144, %edx
movaps %xmm3, %xmm2
movaps %xmm4, %xmm3
jne LBB_main_4 # cond_true44
There are two problems. 1) No need to two loop induction variables. We can
compare against 262144 * 16. 2) Poor register allocation decisions. We should
be able eliminate one of the movaps:
addps %xmm1, %xmm2
subps %xmm3, %xmm2
movaps (%ecx), %xmm4
movaps %xmm2, %xmm2 <=== Eliminate!
addps %xmm4, %xmm2
addl $16, %ecx
incl %edx
cmpl $262144, %edx
movaps %xmm3, %xmm1
movaps %xmm4, %xmm3
jne LBB_main_4 # cond_true44