enhance CanEvaluateZExtd to handle shift left and sext, allowing
more expressions to be promoted and casts eliminated.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93096 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index a6833b8..3ad786b 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -643,17 +643,31 @@
if (Tmp1 == -1) return -1;
Tmp2 = CanEvaluateZExtd(I->getOperand(1), Ty, NumCastsRemoved, TD);
if (Tmp2 == -1) return -1;
+ return 0; // TODO: Could be improved.
+
+ case Instruction::Shl:
+ Tmp1 = CanEvaluateZExtd(I->getOperand(0), Ty, NumCastsRemoved, TD);
+ if (Tmp1 == -1) return -1;
+
+ if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1)))
+ return Tmp1 - CI->getZExtValue();
+
+ // Variable shift, no known zext bits.
+ Tmp2 = CanEvaluateZExtd(I->getOperand(1), Ty, NumCastsRemoved, TD);
+ if (Tmp2 == -1) return -1;
return 0;
- //case Instruction::Shl:
//case Instruction::LShr:
case Instruction::ZExt:
// zext(zext(x)) -> zext(x). Since we're replacing it, it isn't eliminated.
Tmp1 = Ty->getScalarSizeInBits()-OrigTy->getScalarSizeInBits();
return GetLeadingZeros(I, TD)+Tmp1;
- //case Instruction::SExt: zext(sext(x)) -> sext(x) with no upper bits known.
- //case Instruction::Trunc:
+ case Instruction::SExt:
+ // zext(sext(x)) -> sext(x) with no upper bits known.
+ return 0;
+ //case Instruction::Trunc: -> Could turn into AND.
+
case Instruction::Select:
Tmp1 = CanEvaluateZExtd(I->getOperand(1), Ty, NumCastsRemoved, TD);
if (Tmp1 == -1) return -1;