[llvm-commits] [llvm] r163519 - /llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

[Michael Ilseman]

Author: milseman
Date: Mon Sep 10 12:00:37 2012
New Revision: 163519

URL: http://llvm.org/viewvc/llvm-project?rev=163519&view=rev
Log:
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).


Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=163519&r1=163518&r2=163519&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Mon Sep 10 12:00:37 2012
@@ -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!");