Fold multiply by 0 or 1 when in UnsafeFPMath mode in SelectionDAG::getNode().
This folding happens as early as possible for performance reasons, and to make sure it isn't foiled by other transforms (e.g. forming FMAs).
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@163519 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index c6f49c8..d85d41b 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2816,6 +2816,24 @@
if (ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N2))
if (CFP->getValueAPF().isZero())
return N1;
+ } else if (Opcode == ISD::FMUL) {
+ ConstantFPSDNode *CFP = dyn_cast<ConstantFPSDNode>(N1);
+ SDValue V = N2;
+
+ // If the first operand isn't the constant, try the second
+ if (!CFP) {
+ CFP = dyn_cast<ConstantFPSDNode>(N2);
+ V = N1;
+ }
+
+ if (CFP) {
+ // 0*x --> 0
+ if (CFP->isZero())
+ return SDValue(CFP,0);
+ // 1*x --> x
+ if (CFP->isExactlyValue(1.0))
+ return V;
+ }
}
}
assert(VT.isFloatingPoint() && "This operator only applies to FP types!");