[ValueTracking] Replace all uses of ComputeSignBit with computeKnownBits.

This patch finishes off the conversion of ComputeSignBit to computeKnownBits.

Differential Revision: https://reviews.llvm.org/D33166

llvm-svn: 303035
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index b857c04..2a35259 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -162,11 +162,9 @@
     // product is exactly the minimum negative number.
     // E.g. mul i16 with 17 sign bits: 0xff00 * 0xff80 = 0x8000
     // For simplicity we just check if at least one side is not negative.
-    bool LHSNonNegative, LHSNegative;
-    bool RHSNonNegative, RHSNegative;
-    ComputeSignBit(LHS, LHSNonNegative, LHSNegative, /*Depth=*/0, &CxtI);
-    ComputeSignBit(RHS, RHSNonNegative, RHSNegative, /*Depth=*/0, &CxtI);
-    if (LHSNonNegative || RHSNonNegative)
+    KnownBits LHSKnown = computeKnownBits(LHS, /*Depth=*/0, &CxtI);
+    KnownBits RHSKnown = computeKnownBits(RHS, /*Depth=*/0, &CxtI);
+    if (LHSKnown.isNonNegative() || RHSKnown.isNonNegative())
       return true;
   }
   return false;