[IR] Check that arguments of naked function are not used

llvm/docs/LangRef.rst

@@ -2046,7 +2046,8 @@ example:
     attributes.
 ``naked``
     This attribute disables prologue / epilogue emission for the
-    function. This can have very system-specific consequences.
+    function. This can have very system-specific consequences. The arguments of
+    a ``naked`` function can not be referenced through IR values.
 ``"no-inline-line-tables"``
     When this attribute is set to true, the inliner discards source locations
     when inlining code and instead uses the source location of the call site.

llvm/lib/IR/Verifier.cpp

@@ -2777,6 +2777,10 @@ void Verifier::visitFunction(const Function &F) {
   Check(!Attrs.hasAttrSomewhere(Attribute::ElementType),
         "Attribute 'elementtype' can only be applied to a callsite.", &F);
 
+  if (Attrs.hasFnAttr(Attribute::Naked))
+    for (const Argument &Arg : F.args())
+      Check(Arg.use_empty(), "cannot use argument of naked function", &Arg);
+
   // Check that this function meets the restrictions on this calling convention.
   // Sometimes varargs is used for perfectly forwarding thunks, so some of these
   // restrictions can be lifted.

llvm/test/Instrumentation/ThreadSanitizer/tsan_basic.ll

@@ -98,12 +98,12 @@ define void @SwiftErrorCall(ptr swifterror) sanitize_thread {
   ret void
 }
 
-; CHECK-LABEL: @NakedTest(ptr %a)
-; CHECK-NEXT:   call void @foo()
-; CHECK-NEXT:   %tmp1 = load i32, ptr %a, align 4
-; CHECK-NEXT:   ret i32 %tmp1
-define i32 @NakedTest(ptr %a) naked sanitize_thread {
-  call void @foo()
+; CHECK-LABEL: @NakedTest()
+; CHECK-NEXT:  %a = call ptr @foo()
+; CHECK-NEXT:  %tmp1 = load i32, ptr %a, align 4
+; CHECK-NEXT:  ret i32 %tmp1
+define i32 @NakedTest() naked sanitize_thread {
+  %a = call ptr @foo()
   %tmp1 = load i32, ptr %a, align 4
   ret i32 %tmp1
 }

llvm/test/Transforms/Attributor/nonnull.ll

@@ -1048,10 +1048,8 @@ define internal void @naked(ptr dereferenceable(4) %a) naked {
 ; CHECK: Function Attrs: naked
 ; CHECK-LABEL: define {{[^@]+}}@naked
 ; CHECK-SAME: (ptr noundef nonnull dereferenceable(4) [[A:%.*]]) #[[ATTR11:[0-9]+]] {
-; CHECK-NEXT:    call void @use_i32_ptr(ptr nocapture nofree noundef nonnull [[A]])
 ; CHECK-NEXT:    ret void
 ;
-  call void @use_i32_ptr(ptr %a)
   ret void
 }
 ; Avoid nonnull as we do not touch optnone

llvm/test/Transforms/CodeExtractor/PartialInlineAttributes.ll

@@ -81,6 +81,6 @@ attributes #0 = {
 
 ; attributes to drop
 attributes #1 = {
-  alignstack=16 convergent inaccessiblememonly inaccessiblemem_or_argmemonly naked
+  alignstack=16 convergent inaccessiblememonly inaccessiblemem_or_argmemonly
   noreturn readonly argmemonly returns_twice speculatable "thunk"
 }

llvm/test/Transforms/FunctionAttrs/nonnull.ll

@@ -1079,15 +1079,12 @@ define internal void @control(ptr dereferenceable(4) %a) {
 define internal void @naked(ptr dereferenceable(4) %a) naked {
 ; FNATTRS-LABEL: define internal void @naked(
 ; FNATTRS-SAME: ptr dereferenceable(4) [[A:%.*]]) #[[ATTR10:[0-9]+]] {
-; FNATTRS-NEXT:    call void @use_i32_ptr(ptr [[A]])
 ; FNATTRS-NEXT:    ret void
 ;
 ; ATTRIBUTOR-LABEL: define internal void @naked(
 ; ATTRIBUTOR-SAME: ptr nonnull dereferenceable(4) [[A:%.*]]) #[[ATTR11:[0-9]+]] {
-; ATTRIBUTOR-NEXT:    call void @use_i32_ptr(ptr [[A]])
 ; ATTRIBUTOR-NEXT:    ret void
 ;
-  call void @use_i32_ptr(ptr %a)
   ret void
 }
 ; Avoid nonnull as we do not touch optnone

llvm/test/Verifier/naked.ll

@@ -0,0 +1,8 @@
+; RUN: not llvm-as %s -o /dev/null 2>&1 | FileCheck %s
+
+; CHECK: cannot use argument of naked function
+define void @test(ptr %ptr) naked {
+  getelementptr i8, ptr %ptr, i64 1
+  call void @llvm.trap()
+  unreachable
+}