Lower stpcpy_chk when possible.

llvm-svn: 98274

1 files changed, 9 insertions, 6 deletions

diff --git a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
index f5ccebfdefa..c428d2b0b0c 100644
--- a/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/llvm/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -624,11 +624,6 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
     ConstantInt *SizeCI = dyn_cast<ConstantInt>(CI->getOperand(3));
     if (!SizeCI)
       return 0;
-    // If a) we don't have any length information, or b) we know this will
-    // fit then just lower to a plain strcpy. Otherwise we'll keep our
-    // strcpy_chk call which may fail at runtime if the size is too long.
-    // TODO: It might be nice to get a maximum length out of the possible
-    // string lengths for varying.
     if (SizeCI->isAllOnesValue()) {
       Value *Ret = EmitStrCpy(CI->getOperand(1), CI->getOperand(2), B, TD);
       CI->replaceAllUsesWith(Ret);
@@ -638,8 +633,16 @@ bool CodeGenPrepare::OptimizeCallInst(CallInst *CI) {
     return 0;
   }
 
-  // Should be similar to strcpy.
   if (Name == "__stpcpy_chk") {
+    ConstantInt *SizeCI = dyn_cast<ConstantInt>(CI->getOperand(3));
+    if (!SizeCI)
+      return 0;
+    if (SizeCI->isAllOnesValue()) {
+      Value *Ret = EmitStpCpy(CI->getOperand(1), CI->getOperand(2), B, TD);
+      CI->replaceAllUsesWith(Ret);
+      CI->eraseFromParent();
+      return true;
+    }
     return 0;
   }