From bc76ecada07e1905264d02f87499a5ebeb0df816 Mon Sep 17 00:00:00 2001 From: Artur Pilipenko Date: Mon, 22 Aug 2016 13:14:07 +0000 Subject: [PATCH] Revert -r278267 [ValueTracking] An improvement to IR ValueTracking on Non-negative Integers This change cause performance regression on MultiSource/Benchmarks/TSVC/Symbolics-flt/Symbolics-flt from LNT and some other bechmarks. See https://reviews.llvm.org/D18777 for details. llvm-svn: 279433 --- llvm/lib/Analysis/ValueTracking.cpp | 38 +------------------------------ llvm/test/Transforms/BBVectorize/loop1.ll | 2 +- 2 files changed, 2 insertions(+), 38 deletions(-) diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 48305f4..c9fc4d4 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -1259,9 +1259,7 @@ static void computeKnownBitsFromOperator(const Operator *I, APInt &KnownZero, unsigned Opcode = LU->getOpcode(); // Check for operations that have the property that if // both their operands have low zero bits, the result - // will have low zero bits. Also check for operations - // that are known to produce non-negative or negative - // recurrence values. + // will have low zero bits. if (Opcode == Instruction::Add || Opcode == Instruction::Sub || Opcode == Instruction::And || @@ -1287,40 +1285,6 @@ static void computeKnownBitsFromOperator(const Operator *I, APInt &KnownZero, KnownZero = APInt::getLowBitsSet(BitWidth, std::min(KnownZero2.countTrailingOnes(), KnownZero3.countTrailingOnes())); - - auto *OverflowOp = dyn_cast(LU); - if (OverflowOp && OverflowOp->hasNoSignedWrap()) { - // If initial value of recurrence is nonnegative, and we are adding - // a nonnegative number with nsw, the result can only be nonnegative - // or poison value regardless of the number of times we execute the - // add in phi recurrence. If initial value is negative and we are - // adding a negative number with nsw, the result can only be - // negative or poison value. Similar arguments apply to sub and mul. - // - // (add non-negative, non-negative) --> non-negative - // (add negative, negative) --> negative - if (Opcode == Instruction::Add) { - if (KnownZero2.isNegative() && KnownZero3.isNegative()) - KnownZero.setBit(BitWidth - 1); - else if (KnownOne2.isNegative() && KnownOne3.isNegative()) - KnownOne.setBit(BitWidth - 1); - } - - // (sub nsw non-negative, negative) --> non-negative - // (sub nsw negative, non-negative) --> negative - else if (Opcode == Instruction::Sub && LL == I) { - if (KnownZero2.isNegative() && KnownOne3.isNegative()) - KnownZero.setBit(BitWidth - 1); - else if (KnownOne2.isNegative() && KnownZero3.isNegative()) - KnownOne.setBit(BitWidth - 1); - } - - // (mul nsw non-negative, non-negative) --> non-negative - else if (Opcode == Instruction::Mul && KnownZero2.isNegative() && - KnownZero3.isNegative()) - KnownZero.setBit(BitWidth - 1); - } - break; } } diff --git a/llvm/test/Transforms/BBVectorize/loop1.ll b/llvm/test/Transforms/BBVectorize/loop1.ll index 445dec1..70a5def 100644 --- a/llvm/test/Transforms/BBVectorize/loop1.ll +++ b/llvm/test/Transforms/BBVectorize/loop1.ll @@ -83,7 +83,7 @@ for.body: ; preds = %for.body, %entry ; CHECK-UNRL: %add12 = fadd <2 x double> %add7, %mul11 ; CHECK-UNRL: %4 = bitcast double* %arrayidx14 to <2 x double>* ; CHECK-UNRL: store <2 x double> %add12, <2 x double>* %4, align 8 -; CHECK-UNRL: %indvars.iv.next.1 = add nuw nsw i64 %indvars.iv, 2 +; CHECK-UNRL: %indvars.iv.next.1 = add nsw i64 %indvars.iv, 2 ; CHECK-UNRL: %lftr.wideiv.1 = trunc i64 %indvars.iv.next.1 to i32 ; CHECK-UNRL: %exitcond.1 = icmp eq i32 %lftr.wideiv.1, 10 ; CHECK-UNRL: br i1 %exitcond.1, label %for.end, label %for.body -- 2.7.4