diff options
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp | 13 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll | 19 |
2 files changed, 30 insertions, 2 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp index 74a1b6803d..ec1ed66496 100644 --- a/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp +++ b/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp @@ -681,10 +681,19 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask, LHSKnownZero, LHSKnownOne, Depth+1)) return I; + // The low bits of LHS are unchanged by the srem. + KnownZero |= LHSKnownZero & LowBits; + KnownOne |= LHSKnownOne & LowBits; + + // If LHS is non-negative or has all low bits zero, then the upper bits + // are all zero. if (LHSKnownZero[BitWidth-1] || ((LHSKnownZero & LowBits) == LowBits)) - LHSKnownZero |= ~LowBits; + KnownZero |= ~LowBits; - KnownZero |= LHSKnownZero & DemandedMask; + // If LHS is negative and not all low bits are zero, then the upper bits + // are all one. + if (LHSKnownOne[BitWidth-1] && ((LHSKnownOne & LowBits) != 0)) + KnownOne |= ~LowBits; assert(!(KnownZero & KnownOne) && "Bits known to be one AND zero?"); } diff --git a/test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll b/test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll new file mode 100644 index 0000000000..4ab9bf0c3f --- /dev/null +++ b/test/Transforms/InstCombine/2010-01-28-NegativeSRem.ll @@ -0,0 +1,19 @@ +; RUN: opt < %s -instcombine -S | FileCheck %s +; PR6165 + +define i32 @f() { +entry: + br label %BB1 + +BB1: ; preds = %BB1, %entry +; CHECK: BB1: + %x = phi i32 [ -29, %entry ], [ 0, %BB1 ] ; <i32> [#uses=2] + %rem = srem i32 %x, 2 ; <i32> [#uses=1] + %t = icmp eq i32 %rem, -1 ; <i1> [#uses=1] + br i1 %t, label %BB2, label %BB1 +; CHECK-NOT: br i1 false + +BB2: ; preds = %BB1 +; CHECK: BB2: + ret i32 %x +} |