[InstSimplify] fp_binop X, undef --> NaN

The variable operand could be NaN, so it's always safe to propagate NaN.

llvm-svn: 327212

1 files changed, 13 insertions, 14 deletions

diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 8b8a0417aa6..a95a775ead6 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4156,6 +4156,9 @@ static Value *SimplifyFAddInst(Value *Op0, Value *Op1, FastMathFlags FMF,
   if (Constant *C = foldOrCommuteConstant(Instruction::FAdd, Op0, Op1, Q))
     return C;
 
+  if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
+    return ConstantFP::getNaN(Op0->getType());
+
   // fadd X, -0 ==> X
   if (match(Op1, m_NegZero()))
     return Op0;
@@ -4190,6 +4193,9 @@ static Value *SimplifyFSubInst(Value *Op0, Value *Op1, FastMathFlags FMF,
   if (Constant *C = foldOrCommuteConstant(Instruction::FSub, Op0, Op1, Q))
     return C;
 
+  if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
+    return ConstantFP::getNaN(Op0->getType());
+
   // fsub X, 0 ==> X
   if (match(Op1, m_Zero()))
     return Op0;
@@ -4222,6 +4228,9 @@ static Value *SimplifyFMulInst(Value *Op0, Value *Op1, FastMathFlags FMF,
   if (Constant *C = foldOrCommuteConstant(Instruction::FMul, Op0, Op1, Q))
     return C;
 
+  if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
+    return ConstantFP::getNaN(Op0->getType());
+
   // fmul X, 1.0 ==> X
   if (match(Op1, m_FPOne()))
     return Op0;
@@ -4260,13 +4269,8 @@ static Value *SimplifyFDivInst(Value *Op0, Value *Op1, FastMathFlags FMF,
   if (Constant *C = foldOrCommuteConstant(Instruction::FDiv, Op0, Op1, Q))
     return C;
 
-  // undef / X -> undef    (the undef could be a snan).
-  if (match(Op0, m_Undef()))
-    return Op0;
-
-  // X / undef -> undef
-  if (match(Op1, m_Undef()))
-    return Op1;
+  if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
+    return ConstantFP::getNaN(Op0->getType());
 
   // X / 1.0 -> X
   if (match(Op1, m_FPOne()))
@@ -4312,13 +4316,8 @@ static Value *SimplifyFRemInst(Value *Op0, Value *Op1, FastMathFlags FMF,
   if (Constant *C = foldOrCommuteConstant(Instruction::FRem, Op0, Op1, Q))
     return C;
 
-  // undef % X -> undef    (the undef could be a snan).
-  if (match(Op0, m_Undef()))
-    return Op0;
-
-  // X % undef -> undef
-  if (match(Op1, m_Undef()))
-    return Op1;
+  if (isa<UndefValue>(Op0) || isa<UndefValue>(Op1))
+    return ConstantFP::getNaN(Op0->getType());
 
   // 0 % X -> 0
   // Requires that NaNs are off (X could be zero) and signed zeroes are