[InstCombine] X / (X * Y) --> 1.0 / Y
This is similar to the instsimplify fold added with D42385
( rL323716 )
...but this can't be in instsimplify because we're creating/morphing
a different instruction.
llvm-svn: 324927
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index 3cd2403..b1cad6b 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -1523,6 +1523,16 @@
return &I;
}
+ // X / (X * Y) --> 1.0 / Y
+ // Reassociate to (X / X -> 1.0) is legal when NaNs are not allowed.
+ // We can ignore the possibility that X is infinity because INF/INF is NaN.
+ if (I.hasNoNaNs() && I.hasAllowReassoc() &&
+ match(Op1, m_c_FMul(m_Specific(Op0), m_Value(Y)))) {
+ I.setOperand(0, ConstantFP::get(I.getType(), 1.0));
+ I.setOperand(1, Y);
+ return &I;
+ }
+
return nullptr;
}