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add a missed optimization

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@25786 91177308-0d34-0410-b5e6-96231b3b80d8
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Chris Lattner 2006-01-29 09:08:15 +00:00
parent 68a17febc7
commit b638cd89db
1 changed files with 10 additions and 0 deletions
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10
lib/Target/X86/README.txt
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@ -204,3 +204,13 @@ There are two ways to fix this:
disambiguate the pointers.
Number 1 is the preferred solution.
//===---------------------------------------------------------------------===//
The instruction selector sometimes misses folding a load into a compare. The
pattern is written as (cmp reg, (load p)). Because the compare isn't
commutative, it is not matched with the load on both sides. The dag combiner
should be made smart enough to cannonicalize the load into the RHS of a compare
when it can invert the result of the compare for free.