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teach sext optimization to handle truncs from types that are not 

the dest of the sext.

llvm-svn: 93128
This commit is contained in:
Chris Lattner 2010-01-10 20:30:41 +00:00
parent 39d2daa94c
commit 7dd540ee24
2 changed files with 30 additions and 3 deletions
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7
llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
View File

@ -799,6 +799,10 @@ static bool CanEvaluateSExtd(Value *V, const Type *Ty, TargetData *TD) {
if (!I->hasOneUse()) return false; if (!I->hasOneUse()) return false;
switch (I->getOpcode()) { switch (I->getOpcode()) {
case Instruction::SExt: // sext(sext(x)) -> sext(x)
case Instruction::ZExt: // sext(zext(x)) -> zext(x)
case Instruction::Trunc: // sext(trunc(x)) -> trunc(x) or sext(x)
return true;
case Instruction::And: case Instruction::And:
case Instruction::Or: case Instruction::Or:
case Instruction::Xor: case Instruction::Xor:
@ -813,9 +817,6 @@ static bool CanEvaluateSExtd(Value *V, const Type *Ty, TargetData *TD) {
//case Instruction::LShr: TODO //case Instruction::LShr: TODO
//case Instruction::Trunc: TODO //case Instruction::Trunc: TODO
case Instruction::SExt: // sext(sext(x)) -> sext(x)
case Instruction::ZExt: // sext(zext(x)) -> zext(x)
return true;
case Instruction::Select: case Instruction::Select:
return CanEvaluateSExtd(I->getOperand(1), Ty, TD) && return CanEvaluateSExtd(I->getOperand(1), Ty, TD) &&
CanEvaluateSExtd(I->getOperand(2), Ty, TD); CanEvaluateSExtd(I->getOperand(2), Ty, TD);

26
llvm/test/Transforms/InstCombine/cast.ll
View File

@ -523,3 +523,29 @@ define i64 @test53(i32 %A) {
; CHECK-NEXT: %D = and i64 %C, 40186 ; CHECK-NEXT: %D = and i64 %C, 40186
; CHECK-NEXT: ret i64 %D ; CHECK-NEXT: ret i64 %D
} }
define i32 @test54(i64 %A) {
%B = trunc i64 %A to i16
%C = or i16 %B, -32574
%D = and i16 %C, -25350
%E = sext i16 %D to i32
ret i32 %E
; CHECK: @test54
; CHECK-NEXT: %B = trunc i64 %A to i32
; CHECK-NEXT: %C = or i32 %B, -32574
; CHECK-NEXT: %D = and i32 %C, -25350
; CHECK-NEXT: ret i32 %D
}
define i64 @test55(i32 %A) {
%B = trunc i32 %A to i16
%C = or i16 %B, -32574
%D = and i16 %C, -25350
%E = sext i16 %D to i64
ret i64 %E
; CHECK: @test55
; CHECK-NEXT: %B = zext i32 %A to i64
; CHECK-NEXT: %C = or i64 %B, -32574
; CHECK-NEXT: %D = and i64 %C, -25350
; CHECK-NEXT: ret i64 %D
}