[Win64] Don't widen integer literal zero arguments to unprototyped function calls

rnk · rnk · commit d2ad9dfdb998 · 2017-01-03T21:23:35.000Z
The special case to widen the integer literal zero when passed to variadic function calls should only apply to variadic functions, not unprototyped functions. This is consistent with what MSVC does. In this test case, MSVC uses a 4-byte store to pass the 5th argument to 'kr' and an 8-byte store to pass the zero to 'v': void v(int, ...); void kr(); void f(void) { v(1, 2, 3, 4, 0); kr(1, 2, 3, 4, 0); } Aaron Ballman discovered this issue in https://reviews.llvm.org/D28166 llvm-svn: 290906
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
@@ -3571,7 +3571,7 @@ class CodeGenFunction : public CodeGenTypeCache {
 
     // If we still have any arguments, emit them using the type of the argument.
     for (auto *A : llvm::make_range(Arg, ArgRange.end()))
-      ArgTypes.push_back(getVarArgType(A));
+      ArgTypes.push_back(CallArgTypeInfo ? getVarArgType(A) : A->getType());
 
     EmitCallArgs(Args, ArgTypes, ArgRange, CalleeDecl, ParamsToSkip, Order);
   }
diff --git a/clang/test/CodeGen/variadic-null-win64.c b/clang/test/CodeGen/variadic-null-win64.c
@@ -3,15 +3,21 @@
 
 // Make it possible to pass NULL through variadic functions on platforms where
 // NULL has an integer type that is more narrow than a pointer. On such
-// platforms we widen null pointer constants to a pointer-sized integer.
+// platforms we widen null pointer constants passed to variadic functions to a
+// pointer-sized integer. We don't apply this special case to K&R-style
+// unprototyped functions, because MSVC doesn't either.
 
 #define NULL 0
 
 void v(const char *f, ...);
+void kr();
 void f(const char *f) {
   v(f, 1, 2, 3, NULL);
+  kr(f, 1, 2, 3, 0);
 }
 // WINDOWS: define void @f(i8* %f)
 // WINDOWS: call void (i8*, ...) @v(i8* {{.*}}, i32 1, i32 2, i32 3, i64 0)
+// WINDOWS: call void bitcast (void (...)* @kr to void (i8*, i32, i32, i32, i32)*)(i8* {{.*}}, i32 1, i32 2, i32 3, i32 0)
 // LINUX: define void @f(i8* %f)
 // LINUX: call void (i8*, ...) @v(i8* {{.*}}, i32 1, i32 2, i32 3, i32 0)
+// LINUX: call void (i8*, i32, i32, i32, i32, ...) bitcast (void (...)* @kr to void (i8*, i32, i32, i32, i32, ...)*)(i8* %1, i32 1, i32 2, i32 3, i32 0)

Original file line number	Diff line number	Diff line change
`@@ -3571,7 +3571,7 @@ class CodeGenFunction : public CodeGenTypeCache {`
`3571`	`3571`
`3572`	`3572`	`// If we still have any arguments, emit them using the type of the argument.`
`3573`	`3573`	`for (auto *A : llvm::make_range(Arg, ArgRange.end()))`
`3574`		`- ArgTypes.push_back(getVarArgType(A));`
	`3574`	`+ ArgTypes.push_back(CallArgTypeInfo ? getVarArgType(A) : A->getType());`
`3575`	`3575`
`3576`	`3576`	`EmitCallArgs(Args, ArgTypes, ArgRange, CalleeDecl, ParamsToSkip, Order);`
`3577`	`3577`	`}`