[InstSimplify] remove 'nsz' requirement for frem 0, X
From the LangRef definition for frem:
"The value produced is the floating-point remainder of the two operands.
This is the same output as a libm ‘fmod‘ function, but without any
possibility of setting errno. The remainder has the same sign as the
dividend. This instruction is assumed to execute in the default
floating-point environment."
llvm-svn: 327626
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 2b8e23b..773c3ec 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4315,11 +4315,17 @@
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
- // ignored (X could be positive or negative, so the output sign is unknown).
- if (FMF.noNaNs() && FMF.noSignedZeros() && match(Op0, m_AnyZero()))
- return Op0;
+ // Unlike fdiv, the result of frem always matches the sign of the dividend.
+ // The constant match may include undef elements in a vector, so return a full
+ // zero constant as the result.
+ if (FMF.noNaNs()) {
+ // 0 % X -> 0
+ if (match(Op0, m_Zero()))
+ return ConstantFP::getNullValue(Op0->getType());
+ // -0 % X -> -0
+ if (match(Op0, m_NegZero()))
+ return ConstantFP::getNegativeZero(Op0->getType());
+ }
return nullptr;
}