[llvm] b752daa - [InstCombine] Replace getLogBase2 internal helper with ConstantExpr::getExactLogBase2. NFCI.
Simon Pilgrim via llvm-commits
llvm-commits at lists.llvm.org
Sun Oct 11 02:32:32 PDT 2020
Author: Simon Pilgrim
Date: 2020-10-11T10:31:17+01:00
New Revision: b752daa26b641550e1d5b99d4b89230011c2c0cc
URL: https://github.com/llvm/llvm-project/commit/b752daa26b641550e1d5b99d4b89230011c2c0cc
DIFF: https://github.com/llvm/llvm-project/commit/b752daa26b641550e1d5b99d4b89230011c2c0cc.diff
LOG: [InstCombine] Replace getLogBase2 internal helper with ConstantExpr::getExactLogBase2. NFCI.
This exposes the helper for other power-of-2 instcombine folds that I'm intending to add vector support to.
The helper only operated on power-of-2 constants so getExactLogBase2 is a more accurate name.
Added:
Modified:
llvm/include/llvm/IR/Constants.h
llvm/lib/IR/Constants.cpp
llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/IR/Constants.h b/llvm/include/llvm/IR/Constants.h
index 6763d04a53e9..2889df00ec6a 100644
--- a/llvm/include/llvm/IR/Constants.h
+++ b/llvm/include/llvm/IR/Constants.h
@@ -1035,6 +1035,12 @@ class ConstantExpr : public Constant {
return getLShr(C1, C2, true);
}
+ /// If C is a scalar/fixed width vector of known powers of 2, then this
+ /// function returns a new scalar/fixed width vector obtained from logBase2
+ /// of C. Undef vector elements are set to zero.
+ /// Return a null pointer otherwise.
+ static Constant *ConstantExpr::getExactLogBase2(Constant *C);
+
/// Return the identity constant for a binary opcode.
/// The identity constant C is defined as X op C = X and C op X = X for every
/// X when the binary operation is commutative. If the binop is not
diff --git a/llvm/lib/IR/Constants.cpp b/llvm/lib/IR/Constants.cpp
index d0c1e370ce5c..9f83861f2aa6 100644
--- a/llvm/lib/IR/Constants.cpp
+++ b/llvm/lib/IR/Constants.cpp
@@ -2547,6 +2547,35 @@ Constant *ConstantExpr::getAShr(Constant *C1, Constant *C2, bool isExact) {
isExact ? PossiblyExactOperator::IsExact : 0);
}
+Constant *ConstantExpr::getExactLogBase2(Constant *C) {
+ Type *Ty = C->getType();
+ const APInt *IVal;
+ if (match(C, m_APInt(IVal)) && IVal->isPowerOf2())
+ return ConstantInt::get(Ty, IVal->logBase2());
+
+ // FIXME: We can extract pow of 2 of splat constant for scalable vectors.
+ auto *VecTy = dyn_cast<FixedVectorType>(Ty);
+ if (!VecTy)
+ return nullptr;
+
+ SmallVector<Constant *, 4> Elts;
+ for (unsigned I = 0, E = VecTy->getNumElements(); I != E; ++I) {
+ Constant *Elt = C->getAggregateElement(I);
+ if (!Elt)
+ return nullptr;
+ // Note that log2(iN undef) is *NOT* iN undef, because log2(iN undef) u< N.
+ if (isa<UndefValue>(Elt)) {
+ Elts.push_back(Constant::getNullValue(Ty->getScalarType()));
+ continue;
+ }
+ if (!match(Elt, m_APInt(IVal)) || !IVal->isPowerOf2())
+ return nullptr;
+ Elts.push_back(ConstantInt::get(Ty->getScalarType(), IVal->logBase2()));
+ }
+
+ return ConstantVector::get(Elts);
+}
+
Constant *ConstantExpr::getBinOpIdentity(unsigned Opcode, Type *Ty,
bool AllowRHSConstant) {
assert(Instruction::isBinaryOp(Opcode) && "Only binops allowed");
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index e9b57cf38ef1..2da7415b908b 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -95,41 +95,6 @@ static Value *simplifyValueKnownNonZero(Value *V, InstCombinerImpl &IC,
return MadeChange ? V : nullptr;
}
-/// A helper routine of InstCombiner::visitMul().
-///
-/// If C is a scalar/fixed width vector of known powers of 2, then this
-/// function returns a new scalar/fixed width vector obtained from logBase2
-/// of C. Undef elements in a vector are set to zero.
-/// Return a null pointer otherwise.
-static Constant *getLogBase2(Constant *C) {
- Type *Ty = C->getType();
- const APInt *IVal;
- if (match(C, m_APInt(IVal)) && IVal->isPowerOf2())
- return ConstantInt::get(Ty, IVal->logBase2());
-
- // FIXME: We can extract pow of 2 of splat constant for scalable vectors.
- if (!isa<FixedVectorType>(Ty))
- return nullptr;
-
- SmallVector<Constant *, 4> Elts;
- for (unsigned I = 0, E = cast<FixedVectorType>(Ty)->getNumElements(); I != E;
- ++I) {
- Constant *Elt = C->getAggregateElement(I);
- if (!Elt)
- return nullptr;
- // Note that log2(iN undef) is *NOT* iN undef, because log2(iN undef) u< N.
- if (isa<UndefValue>(Elt)) {
- Elts.push_back(Constant::getNullValue(Ty->getScalarType()));
- continue;
- }
- if (!match(Elt, m_APInt(IVal)) || !IVal->isPowerOf2())
- return nullptr;
- Elts.push_back(ConstantInt::get(Ty->getScalarType(), IVal->logBase2()));
- }
-
- return ConstantVector::get(Elts);
-}
-
// TODO: This is a specific form of a much more general pattern.
// We could detect a select with any binop identity constant, or we
// could use SimplifyBinOp to see if either arm of the select reduces.
@@ -219,7 +184,7 @@ Instruction *InstCombinerImpl::visitMul(BinaryOperator &I) {
if (match(&I, m_Mul(m_Value(NewOp), m_Constant(C1)))) {
// Replace X*(2^C) with X << C, where C is either a scalar or a vector.
- if (Constant *NewCst = getLogBase2(C1)) {
+ if (Constant *NewCst = ConstantExpr::getExactLogBase2(C1)) {
BinaryOperator *Shl = BinaryOperator::CreateShl(NewOp, NewCst);
if (I.hasNoUnsignedWrap())
@@ -908,7 +873,7 @@ struct UDivFoldAction {
static Instruction *foldUDivPow2Cst(Value *Op0, Value *Op1,
const BinaryOperator &I,
InstCombinerImpl &IC) {
- Constant *C1 = getLogBase2(cast<Constant>(Op1));
+ Constant *C1 = ConstantExpr::getExactLogBase2(cast<Constant>(Op1));
if (!C1)
llvm_unreachable("Failed to constant fold udiv -> logbase2");
BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, C1);
@@ -929,7 +894,7 @@ static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
Value *N;
if (!match(ShiftLeft, m_Shl(m_Constant(CI), m_Value(N))))
llvm_unreachable("match should never fail here!");
- Constant *Log2Base = getLogBase2(CI);
+ Constant *Log2Base = ConstantExpr::getExactLogBase2(CI);
if (!Log2Base)
llvm_unreachable("getLogBase2 should never fail here!");
N = IC.Builder.CreateAdd(N, Log2Base);
@@ -1146,7 +1111,7 @@ Instruction *InstCombinerImpl::visitSDiv(BinaryOperator &I) {
if (DivisorWasNegative)
Op1 = ConstantExpr::getNeg(cast<Constant>(Op1));
auto *AShr = BinaryOperator::CreateExactAShr(
- Op0, getLogBase2(cast<Constant>(Op1)), I.getName());
+ Op0, ConstantExpr::getExactLogBase2(cast<Constant>(Op1)), I.getName());
if (!DivisorWasNegative)
return AShr;
Builder.Insert(AShr);
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