Hello,
I have attached a patch to allow clang to build the compiler-rt
__clear_cache function on ARM.
The problem is, when targeting ARM, clang thinks it is a builtin with no
external definition. This is incorrect as clang generates a call to the
__clear_cache function.
The change I have made is to add a runtime library function attribute
to the builtin function list. With the attached patch I am able to
build a version of compiler-rt for FreeBSD/ARM that includes
__clear_cache.
Andrew
Index: include/clang/Basic/Builtins.def
===================================================================
--- include/clang/Basic/Builtins.def (revision 183626)
+++ include/clang/Basic/Builtins.def (working copy)
@@ -70,6 +70,8 @@
// f -> this is a libc/libm function without the '__builtin_' prefix. It can
// be followed by ':headername:' to state which header this function
// comes from.
+// i -> this is a runtime library implemented function without the
+// '__builtin_' prefix. It will be implemented in compiter-rt or libgcc.
// p:N: -> this is a printf-like function whose Nth argument is the format
// string.
// P:N: -> similar to the p:N: attribute, but the function is like vprintf
Index: include/clang/Basic/Builtins.h
===================================================================
--- include/clang/Basic/Builtins.h (revision 183626)
+++ include/clang/Basic/Builtins.h (working copy)
@@ -130,6 +130,13 @@
return strchr(GetRecord(ID).Attributes, 'f') != 0;
}
+ /// \brief Determines whether this builtin is a predefined compiler-rt/libgcc
+ /// function, such as "__clear_cache", where we know the signature a
+ /// priori.
+ bool isPredefinedRuntimeFunction(unsigned ID) const {
+ return strchr(GetRecord(ID).Attributes, 'i') != 0;
+ }
+
/// \brief Determines whether this builtin has custom typechecking.
bool hasCustomTypechecking(unsigned ID) const {
return strchr(GetRecord(ID).Attributes, 't') != 0;
Index: include/clang/Basic/BuiltinsAArch64.def
===================================================================
--- include/clang/Basic/BuiltinsAArch64.def (revision 183626)
+++ include/clang/Basic/BuiltinsAArch64.def (working copy)
@@ -15,4 +15,4 @@
// The format of this database matches clang/Basic/Builtins.def.
// In libgcc
-BUILTIN(__clear_cache, "vv*v*", "")
+BUILTIN(__clear_cache, "vv*v*", "i")
Index: include/clang/Basic/BuiltinsARM.def
===================================================================
--- include/clang/Basic/BuiltinsARM.def (revision 183626)
+++ include/clang/Basic/BuiltinsARM.def (working copy)
@@ -15,7 +15,7 @@
// The format of this database matches clang/Basic/Builtins.def.
// In libgcc
-BUILTIN(__clear_cache, "vv*v*", "")
+BUILTIN(__clear_cache, "vv*v*", "i")
BUILTIN(__builtin_thread_pointer, "v*", "")
// Saturating arithmetic
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp (revision 183626)
+++ lib/Sema/SemaDecl.cpp (working copy)
@@ -8694,7 +8694,8 @@
// Builtin functions cannot be defined.
if (unsigned BuiltinID = FD->getBuiltinID()) {
- if (!Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID)) {
+ if (!Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID) &&
+ !Context.BuiltinInfo.isPredefinedRuntimeFunction(BuiltinID)) {
Diag(FD->getLocation(), diag::err_builtin_definition) << FD;
FD->setInvalidDecl();
}
Index: test/Sema/builtin-clear_cache.c
===================================================================
--- test/Sema/builtin-clear_cache.c (revision 0)
+++ test/Sema/builtin-clear_cache.c (working copy)
@@ -0,0 +1,5 @@
+// RUN: %clang_cc1 -triple armv7-none-linux-gnu -fsyntax-only -verify %s
+// RUN: %clang_cc1 -triple aarch64-none-linux-gnu -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+void __clear_cache(void *a, void *b) {}
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