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Another micro-opt.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@42554 91177308-0d34-0410-b5e6-96231b3b80d8
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Bill Wendling 2007-10-02 21:49:31 +00:00
parent 2bb6d459e6
commit 7687bd0b2b
1 changed files with 16 additions and 0 deletions
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16
lib/Target/X86/README.txt
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@ -1306,3 +1306,19 @@ However, ICC caches this information before the loop and produces this:
movl 88(%esp), %eax #481.12
//===---------------------------------------------------------------------===//
This code:
%tmp659 = icmp slt i16 %tmp654, 0 ; <i1> [#uses=1]
br i1 %tmp659, label %cond_true662, label %cond_next715
produces this:
testw %cx, %cx
movswl %cx, %esi
jns LBB4_109 # cond_next715
Shark tells us that using %cx in the testw instruction is sub-optimal. It
suggests using the 32-bit register (which is what ICC uses).
//===---------------------------------------------------------------------===//