EricWF created this revision.
Herald added a subscriber: Prazek.
This patch adds `__builtin_launder`, which is required to implement
`std::launder`. Additionally GCC provides `__builtin_launder`, so thing brings
Clang in-line with GCC.
I'm not exactly sure what magic `__builtin_launder` requires, but based on
previous discussions this patch applies a `@llvm.invariant.group.barrier`. As
noted in previous discussions, this may not be enough to correctly handle
vtables.
https://reviews.llvm.org/D40218
Files:
include/clang/Basic/Builtins.def
include/clang/Basic/DiagnosticSemaKinds.td
lib/CodeGen/CGBuiltin.cpp
lib/Sema/SemaChecking.cpp
test/CodeGen/builtins.c
test/Preprocessor/feature_tests.c
test/Sema/builtins.c
test/SemaCXX/builtins.cpp
Index: test/SemaCXX/builtins.cpp
===================================================================
--- test/SemaCXX/builtins.cpp
+++ test/SemaCXX/builtins.cpp
@@ -53,3 +53,22 @@
void synchronize_args() {
__sync_synchronize(0); // expected-error {{too many arguments}}
}
+
+#define TEST_TYPE(Ptr, Type) \
+static_assert(__is_same(decltype(__builtin_launder(Ptr)), Type), "expected same type")
+
+void test_builtin_launder(char *p, void *vp, const volatile int *ip, const float*& fp) {
+ int x;
+ __builtin_launder(x); // expected-error {{non-pointer argument to '__builtin_launder'}}
+ TEST_TYPE(p, char*);
+ TEST_TYPE(vp, void*);
+ TEST_TYPE(ip, const volatile int*);
+ TEST_TYPE(fp, const float*);
+ char *d = __builtin_launder(p);
+ void *vd = __builtin_launder(vp);
+ const volatile int *id = __builtin_launder(ip);
+ int *id2 = __builtin_launder(ip); // expected-error {{cannot initialize a variable of type 'int *' with an rvalue of type 'const volatile int *'}}
+ const float* fd = __builtin_launder(fp);
+}
+
+#undef TEST_TYPE
Index: test/Sema/builtins.c
===================================================================
--- test/Sema/builtins.c
+++ test/Sema/builtins.c
@@ -248,3 +248,14 @@
return buf;
}
+
+void test_builtin_launder(char *p, void *vp, const volatile int *ip) {
+ __builtin_launder(); // expected-error {{too few arguments to function call, expected 1, have 0}}
+ __builtin_launder(p, p); // expected-error {{too many arguments to function call, expected 1, have 2}}
+ int x;
+ __builtin_launder(x); // expected-error {{non-pointer argument to '__builtin_launder'}}
+ char *d = __builtin_launder(p);
+ void *vd = __builtin_launder(vp);
+ const volatile int *id = __builtin_launder(ip);
+ int *id2 = __builtin_launder(ip); // expected-warning {{discards qualifiers}}
+}
Index: test/Preprocessor/feature_tests.c
===================================================================
--- test/Preprocessor/feature_tests.c
+++ test/Preprocessor/feature_tests.c
@@ -14,6 +14,7 @@
!__has_builtin(__builtin_convertvector) || \
!__has_builtin(__builtin_trap) || \
!__has_builtin(__c11_atomic_init) || \
+ !__has_builtin(__builtin_launder) || \
!__has_feature(attribute_analyzer_noreturn) || \
!__has_feature(attribute_overloadable)
#error Clang should have these
Index: test/CodeGen/builtins.c
===================================================================
--- test/CodeGen/builtins.c
+++ test/CodeGen/builtins.c
@@ -132,6 +132,8 @@
R(extract_return_addr, (&N));
P(signbit, (1.0));
+ R(launder, (&N));
+
return 0;
}
@@ -396,6 +398,20 @@
return __builtin_readcyclecounter();
}
+// CHECK-LABEL: define void @test_builtin_launder
+void test_builtin_launder(int *p) {
+ // CHECK: entry
+ // CHECK-NEXT: %p.addr = alloca i32*
+ // CHECK-NEXT: %d = alloca i32*
+ // CHECK-NEXT: store i32* %p, i32** %p.addr, align 8
+ // CHECK-NEXT: [[TMP:%.*]] = load i32*, i32** %p.addr
+ // CHECK-NEXT: [[TMP1:%.*]] = bitcast i32* [[TMP]] to i8*
+ // CHECK-NEXT: [[TMP2:%.*]] = call i8* @llvm.invariant.group.barrier.p0i8(i8* [[TMP1]])
+ // CHECK-NEXT: [[TMP3:%.*]] = bitcast i8* [[TMP2]] to i32*
+ // CHECK-NEXT: store i32* [[TMP3]], i32** %d
+ int *d = __builtin_launder(p);
+}
+
// Behavior of __builtin_os_log differs between platforms, so only test on X86
#ifdef __x86_64__
Index: lib/Sema/SemaChecking.cpp
===================================================================
--- lib/Sema/SemaChecking.cpp
+++ lib/Sema/SemaChecking.cpp
@@ -850,6 +850,20 @@
return false;
}
+static bool SemaBuiltinLaunder(Sema& S, CallExpr *TheCall) {
+ if (checkArgCount(S, TheCall, 1)) return true;
+ Expr *Arg = TheCall->getArg(0);
+ QualType ArgT = Arg->getType();
+ if (!ArgT->isPointerType()) {
+ S.Diag(TheCall->getLocStart(), diag::err_builtin_launder_non_pointer_arg)
+ << TheCall->getSourceRange();
+ return true;
+ }
+ TheCall->setType(Arg->getType());
+ // FIXME: Add attributes to argument
+ return false; // OK
+}
+
ExprResult
Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
CallExpr *TheCall) {
@@ -967,6 +981,10 @@
if (checkArgCount(*this, TheCall, 1)) return true;
TheCall->setType(Context.IntTy);
break;
+ case Builtin::BI__builtin_launder:
+ if (SemaBuiltinLaunder(*this, TheCall))
+ return ExprError();
+ break;
case Builtin::BI__sync_fetch_and_add:
case Builtin::BI__sync_fetch_and_add_1:
case Builtin::BI__sync_fetch_and_add_2:
Index: lib/CodeGen/CGBuiltin.cpp
===================================================================
--- lib/CodeGen/CGBuiltin.cpp
+++ lib/CodeGen/CGBuiltin.cpp
@@ -1669,6 +1669,11 @@
return RValue::get(nullptr);
}
+ case Builtin::BI__builtin_launder: {
+ Value *Ptr = EmitScalarExpr(E->getArg(0));
+ Ptr = Builder.CreateInvariantGroupBarrier(Ptr);
+ return RValue::get(Ptr);
+ }
case Builtin::BI__sync_fetch_and_add:
case Builtin::BI__sync_fetch_and_sub:
case Builtin::BI__sync_fetch_and_or:
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -9337,4 +9337,7 @@
InGroup<ShadowField>, DefaultIgnore;
def note_shadow_field : Note<"declared here">;
+def err_builtin_launder_non_pointer_arg :
+ Error<"non-pointer argument to '__builtin_launder'">;
+
} // end of sema component.
Index: include/clang/Basic/Builtins.def
===================================================================
--- include/clang/Basic/Builtins.def
+++ include/clang/Basic/Builtins.def
@@ -477,6 +477,7 @@
BUILTIN(__builtin_vsprintf, "ic*cC*a", "nFP:1:")
BUILTIN(__builtin_vsnprintf, "ic*zcC*a", "nFP:2:")
BUILTIN(__builtin_thread_pointer, "v*", "nc")
+BUILTIN(__builtin_launder, "v*v*", "nt")
// GCC exception builtins
BUILTIN(__builtin_eh_return, "vzv*", "r") // FIXME: Takes intptr_t, not size_t!
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