[KnownBits] Add methods for determining if the known bits represent a negative/nonnegative number and add methods for changing the negative/nonnegative state

Summary: This patch adds isNegative, isNonNegative for querying whether the sign bit is known. It also adds makeNegative and makeNonNegative for controlling the sign bit.

Reviewers: RKSimon, spatel, davide

Reviewed By: RKSimon

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D32651

llvm-svn: 301747

1 files changed, 4 insertions, 4 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index 8877799b6ae..0195c5e727c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -589,12 +589,12 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
 
         // If LHS is non-negative or has all low bits zero, then the upper bits
         // are all zero.
-        if (LHSKnown.Zero.isSignBitSet() || LowBits.isSubsetOf(LHSKnown.Zero))
+        if (LHSKnown.isNonNegative() || LowBits.isSubsetOf(LHSKnown.Zero))
           Known.Zero |= ~LowBits;
 
         // If LHS is negative and not all low bits are zero, then the upper bits
         // are all one.
-        if (LHSKnown.One.isSignBitSet() && LowBits.intersects(LHSKnown.One))
+        if (LHSKnown.isNegative() && LowBits.intersects(LHSKnown.One))
           Known.One |= ~LowBits;
 
         assert(!(Known.Zero & Known.One) && "Bits known to be one AND zero?");
@@ -607,8 +607,8 @@ Value *InstCombiner::SimplifyDemandedUseBits(Value *V, APInt DemandedMask,
     if (DemandedMask.isSignBitSet()) {
       computeKnownBits(I->getOperand(0), LHSKnown, Depth + 1, CxtI);
       // If it's known zero, our sign bit is also zero.
-      if (LHSKnown.Zero.isSignBitSet())
-        Known.Zero.setSignBit();
+      if (LHSKnown.isNonNegative())
+        Known.makeNonNegative();
     }
     break;
   case Instruction::URem: {