diff options
| -rw-r--r-- | llvm/lib/Analysis/ValueTracking.cpp | 9 | ||||
| -rw-r--r-- | llvm/test/Analysis/ValueTracking/non-negative-phi-bits.ll | 27 |
2 files changed, 27 insertions, 9 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index b81bf9ec9d1..279d880904e 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -54,12 +54,6 @@ const unsigned MaxDepth = 6; static cl::opt<unsigned> DomConditionsMaxUses("dom-conditions-max-uses", cl::Hidden, cl::init(20)); -// This optimization is known to cause performance regressions is some cases, -// keep it under a temporary flag for now. -static cl::opt<bool> -DontImproveNonNegativePhiBits("dont-improve-non-negative-phi-bits", - cl::Hidden, cl::init(true)); - /// Returns the bitwidth of the given scalar or pointer type. For vector types, /// returns the element type's bitwidth. static unsigned getBitWidth(Type *Ty, const DataLayout &DL) { @@ -1258,9 +1252,6 @@ static void computeKnownBitsFromOperator(const Operator *I, KnownBits &Known, Known.Zero.setLowBits(std::min(Known2.countMinTrailingZeros(), Known3.countMinTrailingZeros())); - if (DontImproveNonNegativePhiBits) - break; - auto *OverflowOp = dyn_cast<OverflowingBinaryOperator>(LU); if (OverflowOp && OverflowOp->hasNoSignedWrap()) { // If initial value of recurrence is nonnegative, and we are adding diff --git a/llvm/test/Analysis/ValueTracking/non-negative-phi-bits.ll b/llvm/test/Analysis/ValueTracking/non-negative-phi-bits.ll new file mode 100644 index 00000000000..059bbaa3c4e --- /dev/null +++ b/llvm/test/Analysis/ValueTracking/non-negative-phi-bits.ll @@ -0,0 +1,27 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt -instcombine < %s -S | FileCheck %s + +define void @test() #0 { +; CHECK-LABEL: @test( +; CHECK-NEXT: entry: +; CHECK-NEXT: br label [[FOR_BODY:%.*]] +; CHECK: for.body: +; CHECK-NEXT: [[INDVARS_IV:%.*]] = phi i64 [ 0, [[ENTRY:%.*]] ], [ [[INDVARS_IV_NEXT:%.*]], [[FOR_BODY]] ] +; CHECK-NEXT: [[INDVARS_IV_NEXT]] = add nuw nsw i64 [[INDVARS_IV]], 1 +; CHECK-NEXT: [[EXITCOND:%.*]] = icmp ult i64 [[INDVARS_IV_NEXT]], 40 +; CHECK-NEXT: br i1 [[EXITCOND]], label [[FOR_END:%.*]], label [[FOR_BODY]] +; CHECK: for.end: +; CHECK-NEXT: ret void +; +entry: + br label %for.body + +for.body: ; preds = %for.body, %entry + %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ] + %indvars.iv.next = add nsw i64 %indvars.iv, 1 + %exitcond = icmp slt i64 %indvars.iv.next, 40 + br i1 %exitcond, label %for.end, label %for.body + +for.end: ; preds = %for.body + ret void +} |
