From a82d52d11df261821c48f7fce5ec3db6d878cff5 Mon Sep 17 00:00:00 2001 From: Andrea Di Biagio Date: Mon, 26 Sep 2016 12:07:23 +0000 Subject: [InstCombine] Teach the udiv folding logic how to handle constant expressions. This patch fixes PR30366. Function foldUDivShl() worked under the assumption that one of the values in input to the function was always an instance of llvm::Instruction. However, function visitUDivOperand() (the only user of foldUDivShl) was clearly violating that precondition; internally, visitUDivOperand() uses pattern matches to check the operands of a udiv. Pattern matchers for binary operators know how to handle both Instruction and ConstantExpr values. This patch fixes the problem in foldUDivShl(). Now we use pattern matchers instead of explicit casts to Instruction. The reduced test case from PR30366 has been added to test file InstCombine/udiv-simplify.ll. Differential Revision: https://reviews.llvm.org/D24565 llvm-svn: 282398 --- .../InstCombine/InstCombineMulDivRem.cpp | 25 ++++++++++++---------- 1 file changed, 14 insertions(+), 11 deletions(-) (limited to 'llvm/lib/Transforms/InstCombine') diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index cd31c63ff28..e1e3cbc5195 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -991,19 +991,22 @@ static Instruction *foldUDivNegCst(Value *Op0, Value *Op1, } // X udiv (C1 << N), where C1 is "1< X >> (N+C2) +// X udiv (zext (C1 << N)), where C1 is "1< X >> (N+C2) static Instruction *foldUDivShl(Value *Op0, Value *Op1, const BinaryOperator &I, InstCombiner &IC) { - Instruction *ShiftLeft = cast(Op1); - if (isa(ShiftLeft)) - ShiftLeft = cast(ShiftLeft->getOperand(0)); - - const APInt &CI = - cast(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(Op1)) - N = IC.Builder->CreateZExt(N, Z->getDestTy()); + Value *ShiftLeft; + if (!match(Op1, m_ZExt(m_Value(ShiftLeft)))) + ShiftLeft = Op1; + + const APInt *CI; + Value *N; + if (!match(ShiftLeft, m_Shl(m_APInt(CI), m_Value(N)))) + llvm_unreachable("match should never fail here!"); + if (*CI != 1) + N = IC.Builder->CreateAdd(N, + ConstantInt::get(N->getType(), CI->logBase2())); + if (Op1 != ShiftLeft) + N = IC.Builder->CreateZExt(N, Op1->getType()); BinaryOperator *LShr = BinaryOperator::CreateLShr(Op0, N); if (I.isExact()) LShr->setIsExact(); -- cgit v1.2.3