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-rw-r--r--lib/Transforms/InstCombine/InstCombineMulDivRem.cpp195
-rw-r--r--test/Transforms/InstCombine/div-shift.ll1
2 files changed, 139 insertions, 57 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index d0d4f41d3b..e94f71917f 100644
--- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -705,40 +705,124 @@ static Value *dyn_castZExtVal(Value *V, Type *Ty) {
return 0;
}
-Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
- Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+namespace {
+const unsigned MaxDepth = 6;
+typedef Instruction *(*FoldUDivOperandCb)(Value *Op0, Value *Op1,
+ const BinaryOperator &I,
+ InstCombiner &IC);
+
+/// \brief Used to maintain state for visitUDivOperand().
+struct UDivFoldAction {
+ FoldUDivOperandCb FoldAction; ///< Informs visitUDiv() how to fold this
+ ///< operand. This can be zero if this action
+ ///< joins two actions together.
+
+ Value *OperandToFold; ///< Which operand to fold.
+ union {
+ Instruction *FoldResult; ///< The instruction returned when FoldAction is
+ ///< invoked.
+
+ size_t SelectLHSIdx; ///< Stores the LHS action index if this action
+ ///< joins two actions together.
+ };
+
+ UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand)
+ : FoldAction(FA), OperandToFold(InputOperand), FoldResult(0) {}
+ UDivFoldAction(FoldUDivOperandCb FA, Value *InputOperand, size_t SLHS)
+ : FoldAction(FA), OperandToFold(InputOperand), SelectLHSIdx(SLHS) {}
+};
+}
- if (Value *V = SimplifyUDivInst(Op0, Op1, TD))
- return ReplaceInstUsesWith(I, V);
+// X udiv 2^C -> X >> C
+static Instruction *foldUDivPow2Cst(Value *Op0, Value *Op1,
+ const BinaryOperator &I, InstCombiner &IC) {
+ const APInt &C = cast<Constant>(Op1)->getUniqueInteger();
+ BinaryOperator *LShr = BinaryOperator::CreateLShr(
+ Op0, ConstantInt::get(Op0->getType(), C.logBase2()));
+ if (I.isExact()) LShr->setIsExact();
+ return LShr;
+}
- // Handle the integer div common cases
- if (Instruction *Common = commonIDivTransforms(I))
- return Common;
+// X udiv C, where C >= signbit
+static Instruction *foldUDivNegCst(Value *Op0, Value *Op1,
+ const BinaryOperator &I, InstCombiner &IC) {
+ Value *ICI = IC.Builder->CreateICmpULT(Op0, cast<ConstantInt>(Op1));
- {
- // X udiv 2^C -> X >> C
- // Check to see if this is an unsigned division with an exact power of 2,
- // if so, convert to a right shift.
- const APInt *C;
- if (match(Op1, m_Power2(C))) {
- BinaryOperator *LShr =
- BinaryOperator::CreateLShr(Op0,
- ConstantInt::get(Op0->getType(),
- C->logBase2()));
- if (I.isExact()) LShr->setIsExact();
- return LShr;
- }
+ return SelectInst::Create(ICI, Constant::getNullValue(I.getType()),
+ ConstantInt::get(I.getType(), 1));
+}
+
+// X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
+static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I,
+ InstCombiner &IC) {
+ Instruction *ShiftLeft = cast<Instruction>(Op1);
+ if (isa<ZExtInst>(ShiftLeft))
+ ShiftLeft = cast<Instruction>(ShiftLeft->getOperand(0));
+
+ const APInt &CI =
+ cast<Constant>(ShiftLeft->getOperand(0))->getUniqueInteger();
+ Value *N = ShiftLeft->getOperand(1);
+ if (CI != 1)
+ N = IC.Builder->CreateAdd(N, ConstantInt::get(N->getType(), CI.logBase2()));
+ if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
+ N = IC.Builder->CreateZExt(N, Z->getDestTy());
+ BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N);
+ if (I.isExact()) LShr->setIsExact();
+ return LShr;
+}
+
+// \brief Recursively visits the possible right hand operands of a udiv
+// instruction, seeing through select instructions, to determine if we can
+// replace the udiv with something simpler. If we find that an operand is not
+// able to simplify the udiv, we abort the entire transformation.
+static size_t visitUDivOperand(Value *Op0, Value *Op1, const BinaryOperator &I,
+ SmallVectorImpl<UDivFoldAction> &Actions,
+ unsigned Depth = 0) {
+ // Check to see if this is an unsigned division with an exact power of 2,
+ // if so, convert to a right shift.
+ if (match(Op1, m_Power2())) {
+ Actions.push_back(UDivFoldAction(foldUDivPow2Cst, Op1));
+ return Actions.size();
}
- if (ConstantInt *C = dyn_cast<ConstantInt>(Op1)) {
+ if (ConstantInt *C = dyn_cast<ConstantInt>(Op1))
// X udiv C, where C >= signbit
if (C->getValue().isNegative()) {
- Value *IC = Builder->CreateICmpULT(Op0, C);
- return SelectInst::Create(IC, Constant::getNullValue(I.getType()),
- ConstantInt::get(I.getType(), 1));
+ Actions.push_back(UDivFoldAction(foldUDivNegCst, C));
+ return Actions.size();
}
+
+ // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
+ if (match(Op1, m_Shl(m_Power2(), m_Value())) ||
+ match(Op1, m_ZExt(m_Shl(m_Power2(), m_Value())))) {
+ Actions.push_back(UDivFoldAction(foldUDivShl, Op1));
+ return Actions.size();
}
+ // The remaining tests are all recursive, so bail out if we hit the limit.
+ if (Depth++ == MaxDepth)
+ return 0;
+
+ if (SelectInst *SI = dyn_cast<SelectInst>(Op1))
+ if (size_t LHSIdx = visitUDivOperand(Op0, SI->getOperand(1), I, Actions))
+ if (visitUDivOperand(Op0, SI->getOperand(2), I, Actions)) {
+ Actions.push_back(UDivFoldAction((FoldUDivOperandCb)0, Op1, LHSIdx-1));
+ return Actions.size();
+ }
+
+ return 0;
+}
+
+Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
+ Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
+
+ if (Value *V = SimplifyUDivInst(Op0, Op1, TD))
+ return ReplaceInstUsesWith(I, V);
+
+ // Handle the integer div common cases
+ if (Instruction *Common = commonIDivTransforms(I))
+ return Common;
+
// (x lshr C1) udiv C2 --> x udiv (C2 << C1)
if (ConstantInt *C2 = dyn_cast<ConstantInt>(Op1)) {
Value *X;
@@ -749,38 +833,6 @@ Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
}
}
- // X udiv (C1 << N), where C1 is "1<<C2" --> X >> (N+C2)
- { const APInt *CI; Value *N;
- if (match(Op1, m_Shl(m_Power2(CI), m_Value(N))) ||
- match(Op1, m_ZExt(m_Shl(m_Power2(CI), m_Value(N))))) {
- if (*CI != 1)
- N = Builder->CreateAdd(N,
- ConstantInt::get(N->getType(), CI->logBase2()));
- if (ZExtInst *Z = dyn_cast<ZExtInst>(Op1))
- N = Builder->CreateZExt(N, Z->getDestTy());
- if (I.isExact())
- return BinaryOperator::CreateExactLShr(Op0, N);
- return BinaryOperator::CreateLShr(Op0, N);
- }
- }
-
- // udiv X, (Select Cond, C1, C2) --> Select Cond, (shr X, C1), (shr X, C2)
- // where C1&C2 are powers of two.
- { Value *Cond; const APInt *C1, *C2;
- if (match(Op1, m_Select(m_Value(Cond), m_Power2(C1), m_Power2(C2)))) {
- // Construct the "on true" case of the select
- Value *TSI = Builder->CreateLShr(Op0, C1->logBase2(), Op1->getName()+".t",
- I.isExact());
-
- // Construct the "on false" case of the select
- Value *FSI = Builder->CreateLShr(Op0, C2->logBase2(), Op1->getName()+".f",
- I.isExact());
-
- // construct the select instruction and return it.
- return SelectInst::Create(Cond, TSI, FSI);
- }
- }
-
// (zext A) udiv (zext B) --> zext (A udiv B)
if (ZExtInst *ZOp0 = dyn_cast<ZExtInst>(Op0))
if (Value *ZOp1 = dyn_castZExtVal(Op1, ZOp0->getSrcTy()))
@@ -788,6 +840,37 @@ Instruction *InstCombiner::visitUDiv(BinaryOperator &I) {
I.isExact()),
I.getType());
+ // (LHS udiv (select (select (...)))) -> (LHS >> (select (select (...))))
+ SmallVector<UDivFoldAction, 6> UDivActions;
+ if (visitUDivOperand(Op0, Op1, I, UDivActions))
+ for (unsigned i = 0, e = UDivActions.size(); i != e; ++i) {
+ FoldUDivOperandCb Action = UDivActions[i].FoldAction;
+ Value *ActionOp1 = UDivActions[i].OperandToFold;
+ Instruction *Inst;
+ if (Action)
+ Inst = Action(Op0, ActionOp1, I, *this);
+ else {
+ // This action joins two actions together. The RHS of this action is
+ // simply the last action we processed, we saved the LHS action index in
+ // the joining action.
+ size_t SelectRHSIdx = i - 1;
+ Value *SelectRHS = UDivActions[SelectRHSIdx].FoldResult;
+ size_t SelectLHSIdx = UDivActions[i].SelectLHSIdx;
+ Value *SelectLHS = UDivActions[SelectLHSIdx].FoldResult;
+ Inst = SelectInst::Create(cast<SelectInst>(ActionOp1)->getCondition(),
+ SelectLHS, SelectRHS);
+ }
+
+ // If this is the last action to process, return it to the InstCombiner.
+ // Otherwise, we insert it before the UDiv and record it so that we may
+ // use it as part of a joining action (i.e., a SelectInst).
+ if (e - i != 1) {
+ Inst->insertBefore(&I);
+ UDivActions[i].FoldResult = Inst;
+ } else
+ return Inst;
+ }
+
return 0;
}
diff --git a/test/Transforms/InstCombine/div-shift.ll b/test/Transforms/InstCombine/div-shift.ll
index 6be5cc4ca1..46d0f9afd7 100644
--- a/test/Transforms/InstCombine/div-shift.ll
+++ b/test/Transforms/InstCombine/div-shift.ll
@@ -1,5 +1,4 @@
; RUN: opt < %s -instcombine -S | FileCheck %s
-; XFAIL: *
define i32 @t1(i16 zeroext %x, i32 %y) nounwind {
entry:
generated by cgit v1.2.3 (git 2.25.1) at 2025-07-14 13:34:22 +0000