[llvm-commits] [llvm] r122960 - /llvm/trunk/lib/Target/README.txt

[Duncan Sands]

Hi Benjamin,

> EarlyCSE does this now (and GVN always did it).

yes, but the issue with the original example (posted on the mailing list) was
that this CSE opportunity was created by an optimization pass that ran *after*
GVN, so wasn't caught by GVN.  Since EarlyCSE runs before GVN, it won't catch
it either.  Unfortunately the README item didn't note this or the original C
code, and I don't seem to have kept a copy of the original email - maybe someone
else did.

Ciao, Duncan.

>
> Modified:
>      llvm/trunk/lib/Target/README.txt
>
> Modified: llvm/trunk/lib/Target/README.txt
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/README.txt?rev=122960&r1=122959&r2=122960&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/README.txt (original)
> +++ llvm/trunk/lib/Target/README.txt Thu Jan  6 07:19:46 2011
> @@ -2009,17 +2009,6 @@
>
>   //===---------------------------------------------------------------------===//
>
> -This compare could fold to false:
> -
> -define i1 @g(i32 a) nounwind readnone {
> -       %add = shl i32 %a, 1
> -       %mul = shl i32 %a, 1
> -       %cmp = icmp ugt i32 %add, %mul
> -       ret i1 %cmp
> -}
> -
> -//===---------------------------------------------------------------------===//
> -
>   This code (from Benchmarks/Dhrystone/dry.c):
>
>   define i32 @Func1(i32, i32) nounwind readnone optsize ssp {
>
>
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