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X86 if conversion + tail merging issues from PR6032.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93372 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2010-01-13 23:28:40 +00:00
parent 22f3b9faac
commit 689339c50f
1 changed files with 20 additions and 0 deletions
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lib/Target/X86/README.txt
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@ -1868,3 +1868,23 @@ carried over to machine instructions. Asm printer (or JIT) can use this
information to add the "lock" prefix.
//===---------------------------------------------------------------------===//
The X86 backend should be able to if-convert SSE comparisons like "ucomisd" to
"cmpsd". For example, this code:
double d1(double x) { return x == x ? x : x + x; }
Compiles into:
_d1:
ucomisd %xmm0, %xmm0
jnp LBB1_2
addsd %xmm0, %xmm0
ret
LBB1_2:
ret
Also, the 'ret's should be shared. This is PR6032.
//===---------------------------------------------------------------------===//