[SystemZ] Use SRST to implement strlen and strnlen

It would also make sense to use it for memchr; I'm working on that now.

llvm-svn: 188547

1 files changed, 61 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 9bb78978e11..3b9f3581a4c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -5616,6 +5616,59 @@ bool SelectionDAGBuilder::visitStrCmpCall(const CallInst &I) {
   return false;
 }
 
+/// visitStrLenCall -- See if we can lower a strlen call into an optimized
+/// form.  If so, return true and lower it, otherwise return false and it
+/// will be lowered like a normal call.
+bool SelectionDAGBuilder::visitStrLenCall(const CallInst &I) {
+  // Verify that the prototype makes sense.  size_t strlen(char *)
+  if (I.getNumArgOperands() != 1)
+    return false;
+
+  const Value *Arg0 = I.getArgOperand(0);
+  if (!Arg0->getType()->isPointerTy() || !I.getType()->isIntegerTy())
+    return false;
+
+  const TargetSelectionDAGInfo &TSI = DAG.getSelectionDAGInfo();
+  std::pair<SDValue, SDValue> Res =
+    TSI.EmitTargetCodeForStrlen(DAG, getCurSDLoc(), DAG.getRoot(),
+                                getValue(Arg0), MachinePointerInfo(Arg0));
+  if (Res.first.getNode()) {
+    processIntegerCallValue(I, Res.first, false);
+    PendingLoads.push_back(Res.second);
+    return true;
+  }
+
+  return false;
+}
+
+/// visitStrNLenCall -- See if we can lower a strnlen call into an optimized
+/// form.  If so, return true and lower it, otherwise return false and it
+/// will be lowered like a normal call.
+bool SelectionDAGBuilder::visitStrNLenCall(const CallInst &I) {
+  // Verify that the prototype makes sense.  size_t strnlen(char *, size_t)
+  if (I.getNumArgOperands() != 2)
+    return false;
+
+  const Value *Arg0 = I.getArgOperand(0), *Arg1 = I.getArgOperand(1);
+  if (!Arg0->getType()->isPointerTy() ||
+      !Arg1->getType()->isIntegerTy() ||
+      !I.getType()->isIntegerTy())
+    return false;
+
+  const TargetSelectionDAGInfo &TSI = DAG.getSelectionDAGInfo();
+  std::pair<SDValue, SDValue> Res =
+    TSI.EmitTargetCodeForStrnlen(DAG, getCurSDLoc(), DAG.getRoot(),
+                                 getValue(Arg0), getValue(Arg1),
+                                 MachinePointerInfo(Arg0));
+  if (Res.first.getNode()) {
+    processIntegerCallValue(I, Res.first, false);
+    PendingLoads.push_back(Res.second);
+    return true;
+  }
+
+  return false;
+}
+
 /// visitUnaryFloatCall - If a call instruction is a unary floating-point
 /// operation (as expected), translate it to an SDNode with the specified opcode
 /// and return true.
@@ -5774,6 +5827,14 @@ void SelectionDAGBuilder::visitCall(const CallInst &I) {
         if (visitStrCmpCall(I))
           return;
         break;
+      case LibFunc::strlen:
+        if (visitStrLenCall(I))
+          return;
+        break;
+      case LibFunc::strnlen:
+        if (visitStrNLenCall(I))
+          return;
+        break;
       }
     }
   }