[PATCH] D14891: Replace assert with early-out in tryEmitFMulAdd

[Steve Canon via cfe-commits]

scanon created this revision.
scanon added reviewers: hfinkel, resistor, lhames.
scanon added a subscriber: cfe-commits.

r253269 exposed a pre-existing issue in tryEmitFMulAdd, where we would assert if a fusable operation had operands with multiple uses (we didn't see it previously because FP_CONTRACT was off by default).  Fix this issue by changing the assert into an early-out where we simply won't try to fuse.

Once this is done, we can try again at enabling FP_CONTRACT ON as a default.

http://reviews.llvm.org/D14891

Files:
  lib/CodeGen/CGExprScalar.cpp

Index: lib/CodeGen/CGExprScalar.cpp
===================================================================
--- lib/CodeGen/CGExprScalar.cpp
+++ lib/CodeGen/CGExprScalar.cpp
@@ -2563,22 +2563,19 @@
   if (CGF.CGM.getCodeGenOpts().getFPContractMode() != CodeGenOptions::FPC_On)
     return nullptr;
 
-  // We have a potentially fusable op. Look for a mul on one of the operands.
+  // We have a potentially fusable op. Look for a mul on one of the operands
+  // that does not have any other uses.
   if (llvm::BinaryOperator* LHSBinOp = dyn_cast<llvm::BinaryOperator>(op.LHS)) {
-    if (LHSBinOp->getOpcode() == llvm::Instruction::FMul) {
-      assert(LHSBinOp->getNumUses() == 0 &&
-             "Operations with multiple uses shouldn't be contracted.");
+    if (LHSBinOp->getOpcode() == llvm::Instruction::FMul &&
+        LHSBinOp->hasNUses(0))
       return buildFMulAdd(LHSBinOp, op.RHS, CGF, Builder, false, isSub);
-    }
-  } else if (llvm::BinaryOperator* RHSBinOp =
-               dyn_cast<llvm::BinaryOperator>(op.RHS)) {
-    if (RHSBinOp->getOpcode() == llvm::Instruction::FMul) {
-      assert(RHSBinOp->getNumUses() == 0 &&
-             "Operations with multiple uses shouldn't be contracted.");
+  }
+  if (llvm::BinaryOperator* RHSBinOp = dyn_cast<llvm::BinaryOperator>(op.RHS)) {
+    if (RHSBinOp->getOpcode() == llvm::Instruction::FMul &&
+        RHSBinOp->hasNUses(0))
       return buildFMulAdd(RHSBinOp, op.LHS, CGF, Builder, isSub, false);
-    }
   }
-
+  
   return nullptr;
 }
 


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