Generate FSQRT from calls to the sqrt function, which

allows appropriate backends to generate a sqrt instruction.

On x86, this isn't done at -O0 because we go through
FastISel instead.  This is a behavior change from before
this series of sqrt patches started.  I think this is OK
considering that compile speed is most important at -O0, but
could be convinced otherwise.

llvm-svn: 82778

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
index 36e7285f207..8431e20d831 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
@@ -4576,6 +4576,15 @@ void SelectionDAGLowering::visitCall(CallInst &I) {
                                    Tmp.getValueType(), Tmp));
           return;
         }
+      } else if (Name == "sqrt" || Name == "sqrtf" || Name == "sqrtl") {
+        if (I.getNumOperands() == 2 &&   // Basic sanity checks.
+            I.getOperand(1)->getType()->isFloatingPoint() &&
+            I.getType() == I.getOperand(1)->getType()) {
+          SDValue Tmp = getValue(I.getOperand(1));
+          setValue(&I, DAG.getNode(ISD::FSQRT, getCurDebugLoc(),
+                                   Tmp.getValueType(), Tmp));
+          return;
+        }
       }
     }
   } else if (isa<InlineAsm>(I.getOperand(0))) {