[InstSimplify] simplify add instruction if two operands are negative
Differential Revision: https://reviews.llvm.org/D49216
llvm-svn: 336881
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 061ce8f..87b1fc5 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -540,6 +540,10 @@
if (match(Op1, m_Zero()))
return Op0;
+ // If two operands are negative, return 0.
+ if (isKnownNegation(Op0, Op1))
+ return Constant::getNullValue(Op0->getType());
+
// X + (Y - X) -> Y
// (Y - X) + X -> Y
// Eg: X + -X -> 0
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index bdfd178..88ed656 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -4511,6 +4511,26 @@
return {SPF_UNKNOWN, SPNB_NA, false};
}
+bool llvm::isKnownNegation(const Value *X, const Value *Y) {
+ assert(X && Y && "Invalid operand");
+
+ // X = sub (0, Y)
+ if (match(X, m_Neg(m_Specific(Y))))
+ return true;
+
+ // Y = sub (0, X)
+ if (match(Y, m_Neg(m_Specific(X))))
+ return true;
+
+ // X = sub (A, B), Y = sub (B, A)
+ Value *A, *B;
+ if (match(X, m_Sub(m_Value(A), m_Value(B))) &&
+ match(Y, m_Sub(m_Specific(B), m_Specific(A))))
+ return true;
+
+ return false;
+}
+
static SelectPatternResult matchSelectPattern(CmpInst::Predicate Pred,
FastMathFlags FMF,
Value *CmpLHS, Value *CmpRHS,