[llvm-commits] [llvm] r112291 - /llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp
Chris Lattner
sabre at nondot.org
Fri Aug 27 14:04:34 PDT 2010
Author: lattner
Date: Fri Aug 27 16:04:34 2010
New Revision: 112291
URL: http://llvm.org/viewvc/llvm-project?rev=112291&view=rev
Log:
remove some special shift cases that have been subsumed into the
more general simplify demanded bits logic.
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp?rev=112291&r1=112290&r2=112291&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineShifts.cpp Fri Aug 27 16:04:34 2010
@@ -59,7 +59,7 @@
Instruction *InstCombiner::FoldShiftByConstant(Value *Op0, ConstantInt *Op1,
BinaryOperator &I) {
bool isLeftShift = I.getOpcode() == Instruction::Shl;
-
+
// See if we can simplify any instructions used by the instruction whose sole
// purpose is to compute bits we don't care about.
uint32_t TypeBits = Op0->getType()->getScalarSizeInBits();
@@ -288,39 +288,17 @@
ConstantInt::get(Ty, AmtSum));
}
- if (ShiftOp->getOpcode() == Instruction::LShr &&
- I.getOpcode() == Instruction::AShr) {
- if (AmtSum >= TypeBits)
- return ReplaceInstUsesWith(I, Constant::getNullValue(I.getType()));
-
- // ((X >>u C1) >>s C2) -> (X >>u (C1+C2)) since C1 != 0.
- return BinaryOperator::CreateLShr(X, ConstantInt::get(Ty, AmtSum));
- }
-
- if (ShiftOp->getOpcode() == Instruction::AShr &&
- I.getOpcode() == Instruction::LShr) {
- // ((X >>s C1) >>u C2) -> ((X >>s (C1+C2)) & mask) since C1 != 0.
- if (AmtSum >= TypeBits)
- AmtSum = TypeBits-1;
-
- Value *Shift = Builder->CreateAShr(X, ConstantInt::get(Ty, AmtSum));
-
- APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
- return BinaryOperator::CreateAnd(Shift,
- ConstantInt::get(I.getContext(), Mask));
- }
-
- // Okay, if we get here, one shift must be left, and the other shift must be
- // right. See if the amounts are equal.
if (ShiftAmt1 == ShiftAmt2) {
// If we have ((X >>? C) << C), turn this into X & (-1 << C).
- if (I.getOpcode() == Instruction::Shl) {
+ if (I.getOpcode() == Instruction::Shl &&
+ ShiftOp->getOpcode() != Instruction::Shl) {
APInt Mask(APInt::getHighBitsSet(TypeBits, TypeBits - ShiftAmt1));
return BinaryOperator::CreateAnd(X,
ConstantInt::get(I.getContext(),Mask));
}
// If we have ((X << C) >>u C), turn this into X & (-1 >>u C).
- if (I.getOpcode() == Instruction::LShr) {
+ if (I.getOpcode() == Instruction::LShr &&
+ ShiftOp->getOpcode() == Instruction::Shl) {
APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt1));
return BinaryOperator::CreateAnd(X,
ConstantInt::get(I.getContext(), Mask));
@@ -329,7 +307,8 @@
uint32_t ShiftDiff = ShiftAmt2-ShiftAmt1;
// (X >>? C1) << C2 --> X << (C2-C1) & (-1 << C2)
- if (I.getOpcode() == Instruction::Shl) {
+ if (I.getOpcode() == Instruction::Shl &&
+ ShiftOp->getOpcode() != Instruction::Shl) {
assert(ShiftOp->getOpcode() == Instruction::LShr ||
ShiftOp->getOpcode() == Instruction::AShr);
Value *Shift = Builder->CreateShl(X, ConstantInt::get(Ty, ShiftDiff));
@@ -340,7 +319,8 @@
}
// (X << C1) >>u C2 --> X >>u (C2-C1) & (-1 >> C2)
- if (I.getOpcode() == Instruction::LShr) {
+ if (I.getOpcode() == Instruction::LShr &&
+ ShiftOp->getOpcode() == Instruction::Shl) {
assert(ShiftOp->getOpcode() == Instruction::Shl);
Value *Shift = Builder->CreateLShr(X, ConstantInt::get(Ty, ShiftDiff));
@@ -355,9 +335,8 @@
uint32_t ShiftDiff = ShiftAmt1-ShiftAmt2;
// (X >>? C1) << C2 --> X >>? (C1-C2) & (-1 << C2)
- if (I.getOpcode() == Instruction::Shl) {
- assert(ShiftOp->getOpcode() == Instruction::LShr ||
- ShiftOp->getOpcode() == Instruction::AShr);
+ if (I.getOpcode() == Instruction::Shl &&
+ ShiftOp->getOpcode() != Instruction::Shl) {
Value *Shift = Builder->CreateBinOp(ShiftOp->getOpcode(), X,
ConstantInt::get(Ty, ShiftDiff));
@@ -367,8 +346,8 @@
}
// (X << C1) >>u C2 --> X << (C1-C2) & (-1 >> C2)
- if (I.getOpcode() == Instruction::LShr) {
- assert(ShiftOp->getOpcode() == Instruction::Shl);
+ if (I.getOpcode() == Instruction::LShr &&
+ ShiftOp->getOpcode() == Instruction::Shl) {
Value *Shift = Builder->CreateShl(X, ConstantInt::get(Ty, ShiftDiff));
APInt Mask(APInt::getLowBitsSet(TypeBits, TypeBits - ShiftAmt2));
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