diff options
Diffstat (limited to 'llvm/lib/Analysis/ValueTracking.cpp')
| -rw-r--r-- | llvm/lib/Analysis/ValueTracking.cpp | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp index 5e9f8cc8d1b..fd519e2ad5c 100644 --- a/llvm/lib/Analysis/ValueTracking.cpp +++ b/llvm/lib/Analysis/ValueTracking.cpp @@ -54,6 +54,12 @@ 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) { @@ -1292,6 +1298,9 @@ 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 |
