diff options
| -rw-r--r-- | lib/Analysis/ScalarEvolution.cpp | 21 | ||||
| -rw-r--r-- | test/Transforms/IndVarSimplify/shrunk-constant.ll | 14 |
2 files changed, 32 insertions, 3 deletions
diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index ca805bd867..3731fdfc71 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -68,6 +68,7 @@ #include "llvm/Analysis/ConstantFolding.h" #include "llvm/Analysis/Dominators.h" #include "llvm/Analysis/LoopInfo.h" +#include "llvm/Analysis/ValueTracking.h" #include "llvm/Assembly/Writer.h" #include "llvm/Target/TargetData.h" #include "llvm/Support/CommandLine.h" @@ -2394,14 +2395,28 @@ SCEVHandle ScalarEvolution::createSCEV(Value *V) { if (CI->isAllOnesValue()) return getSCEV(U->getOperand(0)); const APInt &A = CI->getValue(); - unsigned Ones = A.countTrailingOnes(); - if (APIntOps::isMask(Ones, A)) + + // Instcombine's ShrinkDemandedConstant may strip bits out of + // constants, obscuring what would otherwise be a low-bits mask. + // Use ComputeMaskedBits to compute what ShrinkDemandedConstant + // knew about to reconstruct a low-bits mask value. + unsigned LZ = A.countLeadingZeros(); + unsigned BitWidth = A.getBitWidth(); + APInt AllOnes = APInt::getAllOnesValue(BitWidth); + APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0); + ComputeMaskedBits(U->getOperand(0), AllOnes, KnownZero, KnownOne, TD); + + APInt EffectiveMask = APInt::getLowBitsSet(BitWidth, BitWidth - LZ); + + if (LZ != 0 && !((~A & ~KnownZero) & EffectiveMask)) { return getZeroExtendExpr(getTruncateExpr(getSCEV(U->getOperand(0)), - IntegerType::get(Ones)), + IntegerType::get(BitWidth - LZ)), U->getType()); + } } break; + case Instruction::Or: // If the RHS of the Or is a constant, we may have something like: // X*4+1 which got turned into X*4|1. Handle this as an Add so loop diff --git a/test/Transforms/IndVarSimplify/shrunk-constant.ll b/test/Transforms/IndVarSimplify/shrunk-constant.ll new file mode 100644 index 0000000000..f783b8305e --- /dev/null +++ b/test/Transforms/IndVarSimplify/shrunk-constant.ll @@ -0,0 +1,14 @@ +; RUN: llvm-as < %s | opt -iv-users -analyze | grep store + +define fastcc void @foo() nounwind { +entry: + br label %loop + +loop: + %i = phi i32 [ 0, %entry ], [ %t2, %loop ] + %t0 = add i32 %i, 9 + %t1 = and i32 %t0, 9 + store i32 %t1, i32* null + %t2 = add i32 %i, 8 + br label %loop +} |