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It is OK to remove extra cast if operation is EQ/NE even though source 

and destination sign may not match but other conditions are met.

llvm-svn: 31056
This commit is contained in:
Devang Patel 2006-10-19 20:59:13 +00:00
parent 88afd00d1d
commit 5d6df959e3
2 changed files with 12 additions and 2 deletions
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5
llvm/lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -4795,8 +4795,9 @@ Instruction *InstCombiner::visitSetCondInstWithCastAndCast(SetCondInst &SCI) {
// %B = setgt short %X, 1330
//
// because %A may have negative value.
// However, it is OK if SrcTy is bool. See cast-set.ll testcase.
if (isSignSrc == isSignDest || SrcTy == Type::BoolTy)
// However, it is OK if SrcTy is bool (See cast-set.ll testcase)
// OR operation is EQ/NE.
if (isSignSrc == isSignDest || SrcTy == Type::BoolTy || SCI.isEquality())
RHSCIOp = Res;
else
return 0;

9
llvm/test/Regression/Transforms/InstCombine/2006-10-19-SignedToUnsignedCastAndConst-2.ll Normal file
View File

@ -0,0 +1,9 @@
; The optimizer should be able to remove cast operation here.
; RUN: llvm-as %s -o - | opt -instcombine | llvm-dis | not grep 'cast.*int'
bool %eq_signed_to_small_unsigned(sbyte %SB) {
%Y = cast sbyte %SB to uint ; <uint> [#uses=1]
%C = seteq uint %Y, 17 ; <bool> [#uses=1]
ret bool %C
}