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

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@94783 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 19 insertions, 5 deletions

diff --git a/lib/Transforms/Scalar/SimplifyLibCalls.cpp b/lib/Transforms/Scalar/SimplifyLibCalls.cpp
index a49da9ce9e..fc23c420cc 100644
--- a/lib/Transforms/Scalar/SimplifyLibCalls.cpp
+++ b/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;
diff --git a/test/Transforms/SimplifyLibCalls/strcpy_chk.ll b/test/Transforms/SimplifyLibCalls/strcpy_chk.ll
new file mode 100644
index 0000000000..422cbd9345
--- /dev/null
+++ b/test/Transforms/SimplifyLibCalls/strcpy_chk.ll
@@ -0,0 +1,12 @@
+; RUN: opt < %s -simplify-libcalls -S | FileCheck %s
+@a = common global [60 x i8] zeroinitializer, align 1 ; <[60 x i8]*> [#uses=1]
+@.str = private constant [8 x i8] c"abcdefg\00"   ; <[8 x i8]*> [#uses=1]
+
+define i8* @foo() nounwind {
+; CHECK: @foo
+; CHECK-NEXT: call i8* @strcpy
+  %call = call i8* @__strcpy_chk(i8* getelementptr inbounds ([60 x i8]* @a, i32 0, i32 0), i8* getelementptr inbounds ([8 x i8]* @.str, i32 0, i32 0), i32 60) ; <i8*> [#uses=1]
+  ret i8* %call
+}
+
+declare i8* @__strcpy_chk(i8*, i8*, i32) nounwind