[SimplifyLibCalls] sprintf doesn't copy null bytes

sprintf doesn't read or copy the terminating null byte from it's string
operands.  sprintf will append it's own after processing all of the
format specifiers.

This fixes PR27526.

llvm-svn: 267580

diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 104a82c..70f6422 100644 (file)
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1995,9 +1995,10 @@ Value *LibCallSimplifier::optimizeSPrintFString(CallInst *CI, IRBuilder<> &B) {
     Value *Len = emitStrLen(CI->getArgOperand(2), B, DL, TLI);
     if (!Len)
       return nullptr;
-    Value *IncLen =
-        B.CreateAdd(Len, ConstantInt::get(Len->getType(), 1), "leninc");
-    B.CreateMemCpy(CI->getArgOperand(0), CI->getArgOperand(2), IncLen, 1);
+    B.CreateMemCpy(CI->getArgOperand(0), CI->getArgOperand(2), Len, 1);
+    Value *PtrToNullByte =
+        B.CreateGEP(B.getInt8Ty(), CI->getArgOperand(0), Len, "nul");
+    B.CreateStore(B.getInt8(0), PtrToNullByte);
 
     // The sprintf result is the unincremented number of bytes in the string.
     return B.CreateIntCast(Len, CI->getType(), false);

diff --git a/llvm/test/Transforms/InstCombine/sprintf-1.ll b/llvm/test/Transforms/InstCombine/sprintf-1.ll
index ddf2f2f..0c7fbcb 100644 (file)
--- a/llvm/test/Transforms/InstCombine/sprintf-1.ll
+++ b/llvm/test/Transforms/InstCombine/sprintf-1.ll
@@ -65,8 +65,9 @@ define void @test_simplify5(i8* %dst, i8* %str) {
   %fmt = getelementptr [3 x i8], [3 x i8]* @percent_s, i32 0, i32 0
   call i32 (i8*, i8*, ...) @sprintf(i8* %dst, i8* %fmt, i8* %str)
 ; CHECK-NEXT: [[STRLEN:%[a-z0-9]+]] = call i32 @strlen(i8* %str)
-; CHECK-NEXT: [[LENINC:%[a-z0-9]+]] = add i32 [[STRLEN]], 1
-; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %str, i32 [[LENINC]], i32 1, i1 false)
+; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i32(i8* %dst, i8* %str, i32 [[STRLEN]], i32 1, i1 false)
+; CHECK-NEXT: [[NUL:%[a-z0-9]+]] = getelementptr i8, i8* %dst, i32 [[STRLEN]]
+; CHECK-NEXT: store i8 0, i8* [[NUL]], align 1
   ret void
 ; CHECK-NEXT: ret void
 }