move a trunc-specific xform out of commonIntCastTransforms into visitTrunc
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@92768 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 103630e..e2bb3fb 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -28,19 +28,25 @@
Offset = CI->getZExtValue();
Scale = 0;
return ConstantInt::get(Type::getInt32Ty(Val->getContext()), 0);
- } else if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
+ }
+
+ if (BinaryOperator *I = dyn_cast<BinaryOperator>(Val)) {
if (ConstantInt *RHS = dyn_cast<ConstantInt>(I->getOperand(1))) {
if (I->getOpcode() == Instruction::Shl) {
// This is a value scaled by '1 << the shift amt'.
Scale = 1U << RHS->getZExtValue();
Offset = 0;
return I->getOperand(0);
- } else if (I->getOpcode() == Instruction::Mul) {
+ }
+
+ if (I->getOpcode() == Instruction::Mul) {
// This value is scaled by 'RHS'.
Scale = RHS->getZExtValue();
Offset = 0;
return I->getOperand(0);
- } else if (I->getOpcode() == Instruction::Add) {
+ }
+
+ if (I->getOpcode() == Instruction::Add) {
// We have X+C. Check to see if we really have (X*C2)+C1,
// where C1 is divisible by C2.
unsigned SubScale;
@@ -650,18 +656,6 @@
ConstantInt::get(CI.getType(), 1));
}
break;
-
- case Instruction::Shl: {
- // Canonicalize trunc inside shl, if we can.
- ConstantInt *CI = dyn_cast<ConstantInt>(Op1);
- if (CI && DestBitSize < SrcBitSize &&
- CI->getLimitedValue(DestBitSize) < DestBitSize) {
- Value *Op0c = Builder->CreateTrunc(Op0, DestTy, Op0->getName());
- Value *Op1c = Builder->CreateTrunc(Op1, DestTy, Op1->getName());
- return BinaryOperator::CreateShl(Op0c, Op1c);
- }
- break;
- }
}
return 0;
}
@@ -684,7 +678,7 @@
return new ICmpInst(ICmpInst::ICMP_NE, Src, Zero);
}
- // Optimize trunc(lshr(), c) to pull the shift through the truncate.
+ // Optimize trunc(lshr(x, c)) to pull the shift through the truncate.
ConstantInt *ShAmtV = 0;
Value *ShiftOp = 0;
if (Src->hasOneUse() &&
@@ -704,6 +698,21 @@
return BinaryOperator::CreateLShr(V1, V2);
}
}
+
+ // Transform trunc(shl(X, C)) -> shl(trunc(X), C)
+ if (Src->hasOneUse() &&
+ match(Src, m_Shl(m_Value(ShiftOp), m_ConstantInt(ShAmtV)))) {
+ uint32_t ShAmt = ShAmtV->getLimitedValue(SrcBitWidth);
+ if (ShAmt >= DestBitWidth) // All zeros.
+ return ReplaceInstUsesWith(CI, Constant::getNullValue(Ty));
+
+ // Okay, we can shrink this. Truncate the input, then return a new
+ // shift.
+ Value *V1 = Builder->CreateTrunc(ShiftOp, Ty, ShiftOp->getName());
+ Value *V2 = ConstantExpr::getTrunc(ShAmtV, Ty);
+ return BinaryOperator::CreateShl(V1, V2);
+ }
+
return 0;
}