Make strcpy_chk lower to strcpy if we have a safe size.

llvm-svn: 94783

1 files changed, 7 insertions, 5 deletions

diff --git a/llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index a49da9ce9e5..fc23c420cc8 100644
--- a/llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Scalar/SimplifyLibCalls.cpp
@@ -1203,9 +1203,6 @@ struct MemMoveChkOpt : public LibCallOptimization {
 
 struct StrCpyChkOpt : public LibCallOptimization {
   virtual Value *CallOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
-    // These optimizations require TargetData.
-    if (!TD) return 0;
-
     const FunctionType *FT = Callee->getFunctionType();
     if (FT->getNumParams() != 3 || FT->getReturnType() != FT->getParamType(0) ||
         !isa<PointerType>(FT->getParamType(0)) ||
@@ -1217,8 +1214,13 @@ struct StrCpyChkOpt : public LibCallOptimization {
     if (!SizeCI)
       return 0;
     
-    // We don't have any length information, just lower to a plain strcpy.
-    if (SizeCI->isAllOnesValue())
+    // 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() ||
+        SizeCI->getZExtValue() >= GetStringLength(CI->getOperand(2)))
       return EmitStrCpy(CI->getOperand(1), CI->getOperand(2), B);
 
     return 0;