[llvm] r299704 - [InstCombine] Remove redundant combine from visitAnd
Craig Topper via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 6 13:41:48 PDT 2017
Author: ctopper
Date: Thu Apr 6 15:41:48 2017
New Revision: 299704
URL: http://llvm.org/viewvc/llvm-project?rev=299704&view=rev
Log:
[InstCombine] Remove redundant combine from visitAnd
This combine is fully handled by SimplifyDemandedInstructionBits as of r299658 where I fixed this code to ensure the Add/Sub had only a single user. Otherwise it would fire and create additional instructions. That fix resulted in an improvement to code generated for tsan which is why I committed it before deleting.
Differential Revision: https://reviews.llvm.org/D31543
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp?rev=299704&r1=299703&r2=299704&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp Thu Apr 6 15:41:48 2017
@@ -295,77 +295,6 @@ Value *InstCombiner::insertRangeTest(Val
return Builder->CreateICmp(Pred, VMinusLo, HiMinusLo);
}
-/// Returns true iff Val consists of one contiguous run of 1s with any number
-/// of 0s on either side. The 1s are allowed to wrap from LSB to MSB,
-/// so 0x000FFF0, 0x0000FFFF, and 0xFF0000FF are all runs. 0x0F0F0000 is
-/// not, since all 1s are not contiguous.
-static bool isRunOfOnes(ConstantInt *Val, uint32_t &MB, uint32_t &ME) {
- const APInt& V = Val->getValue();
- uint32_t BitWidth = Val->getType()->getBitWidth();
- if (!V.isShiftedMask()) return false;
-
- // look for the first zero bit after the run of ones
- MB = BitWidth - ((V - 1) ^ V).countLeadingZeros();
- // look for the first non-zero bit
- ME = V.getActiveBits();
- return true;
-}
-
-/// This is part of an expression (LHS +/- RHS) & Mask, where isSub determines
-/// whether the operator is a sub. If we can fold one of the following xforms:
-///
-/// ((A & N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == Mask
-/// ((A | N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == 0
-/// ((A ^ N) +/- B) & Mask -> (A +/- B) & Mask iff N&Mask == 0
-///
-/// return (A +/- B).
-///
-Value *InstCombiner::FoldLogicalPlusAnd(Value *LHS, Value *RHS,
- ConstantInt *Mask, bool isSub,
- Instruction &I) {
- Instruction *LHSI = dyn_cast<Instruction>(LHS);
- if (!LHSI || LHSI->getNumOperands() != 2 ||
- !isa<ConstantInt>(LHSI->getOperand(1))) return nullptr;
-
- ConstantInt *N = cast<ConstantInt>(LHSI->getOperand(1));
-
- switch (LHSI->getOpcode()) {
- default: return nullptr;
- case Instruction::And:
- if (ConstantExpr::getAnd(N, Mask) == Mask) {
- // If the AndRHS is a power of two minus one (0+1+), this is simple.
- if ((Mask->getValue().countLeadingZeros() +
- Mask->getValue().countPopulation()) ==
- Mask->getValue().getBitWidth())
- break;
-
- // Otherwise, if Mask is 0+1+0+, and if B is known to have the low 0+
- // part, we don't need any explicit masks to take them out of A. If that
- // is all N is, ignore it.
- uint32_t MB = 0, ME = 0;
- if (isRunOfOnes(Mask, MB, ME)) { // begin/end bit of run, inclusive
- uint32_t BitWidth = cast<IntegerType>(RHS->getType())->getBitWidth();
- APInt Mask(APInt::getLowBitsSet(BitWidth, MB-1));
- if (MaskedValueIsZero(RHS, Mask, 0, &I))
- break;
- }
- }
- return nullptr;
- case Instruction::Or:
- case Instruction::Xor:
- // If the AndRHS is a power of two minus one (0+1+), and N&Mask == 0
- if ((Mask->getValue().countLeadingZeros() +
- Mask->getValue().countPopulation()) == Mask->getValue().getBitWidth()
- && ConstantExpr::getAnd(N, Mask)->isNullValue())
- break;
- return nullptr;
- }
-
- if (isSub)
- return Builder->CreateSub(LHSI->getOperand(0), RHS, "fold");
- return Builder->CreateAdd(LHSI->getOperand(0), RHS, "fold");
-}
-
/// Classify (icmp eq (A & B), C) and (icmp ne (A & B), C) as matching patterns
/// that can be simplified.
/// One of A and B is considered the mask. The other is the value. This is
@@ -1328,26 +1257,7 @@ Instruction *InstCombiner::visitAnd(Bina
break;
}
- case Instruction::Add:
- // ((A & N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == AndRHS.
- // ((A | N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
- // ((A ^ N) + B) & AndRHS -> (A + B) & AndRHS iff N&AndRHS == 0
- if (Op0I->hasOneUse()) {
- if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, false, I))
- return BinaryOperator::CreateAnd(V, AndRHS);
- if (Value *V = FoldLogicalPlusAnd(Op0RHS, Op0LHS, AndRHS, false, I))
- return BinaryOperator::CreateAnd(V, AndRHS); // Add commutes
- }
- break;
-
case Instruction::Sub:
- // ((A & N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == AndRHS.
- // ((A | N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
- // ((A ^ N) - B) & AndRHS -> (A - B) & AndRHS iff N&AndRHS == 0
- if (Op0I->hasOneUse())
- if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
- return BinaryOperator::CreateAnd(V, AndRHS);
-
// -x & 1 -> x & 1
if (AndRHSMask == 1 && match(Op0LHS, m_Zero()))
return BinaryOperator::CreateAnd(Op0RHS, AndRHS);
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h?rev=299704&r1=299703&r2=299704&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineInternal.h Thu Apr 6 15:41:48 2017
@@ -653,8 +653,6 @@ private:
Instruction *OptAndOp(BinaryOperator *Op, ConstantInt *OpRHS,
ConstantInt *AndRHS, BinaryOperator &TheAnd);
- Value *FoldLogicalPlusAnd(Value *LHS, Value *RHS, ConstantInt *Mask,
- bool isSub, Instruction &I);
Value *insertRangeTest(Value *V, const APInt &Lo, const APInt &Hi,
bool isSigned, bool Inside);
Instruction *PromoteCastOfAllocation(BitCastInst &CI, AllocaInst &AI);
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