[gcc r14-4822] target: Support heap-based trampolines

[Iain D Sandoe <iains@gcc.gnu.org>]

https://gcc.gnu.org/g:cbf6da166ea7993e166dcb121fc7b9ef4ec87c89

commit r14-4822-gcbf6da166ea7993e166dcb121fc7b9ef4ec87c89
Author: Andrew Burgess <andrew.burgess@embecosm.com>
Date:   Sat Aug 5 14:56:31 2023 +0200

    target: Support heap-based trampolines
    
    Enable -ftrampoline-impl=heap by default if we are on macOS 11
    or later.
    
    Co-Authored-By: Maxim Blinov <maxim.blinov@embecosm.com>
    Co-Authored-By: Francois-Xavier Coudert <fxcoudert@gcc.gnu.org>
    Co-Authored-By: Iain Sandoe <iain@sandoe.co.uk>
    
    gcc/ChangeLog:
    
            * config.gcc: Default to heap trampolines on macOS 11 and above.
            * config/i386/darwin.h: Define X86_CUSTOM_FUNCTION_TEST.
            * config/i386/i386.h: Define X86_CUSTOM_FUNCTION_TEST.
            * config/i386/i386.cc: Use X86_CUSTOM_FUNCTION_TEST.

Diff:
---
 gcc/config.gcc           | 11 +++++++++++
 gcc/config/i386/darwin.h |  6 ++++++
 gcc/config/i386/i386.cc  |  2 +-
 gcc/config/i386/i386.h   |  6 ++++++
 4 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/gcc/config.gcc b/gcc/config.gcc
index 0782cbc6e915..606d3a8513ea 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1171,6 +1171,17 @@ case ${target} in
   ;;
 esac
 
+# Figure out if we need to enable heap trampolines by default
+case ${target} in
+*-*-darwin2*)
+  # Currently, we do this for macOS 11 and above.
+  tm_defines="$tm_defines HEAP_TRAMPOLINES_INIT=1"
+  ;;
+*)
+  tm_defines="$tm_defines HEAP_TRAMPOLINES_INIT=0"
+  ;;
+esac
+
 case ${target} in
 aarch64*-*-elf | aarch64*-*-fuchsia* | aarch64*-*-rtems*)
 	tm_file="${tm_file} elfos.h newlib-stdint.h"
diff --git a/gcc/config/i386/darwin.h b/gcc/config/i386/darwin.h
index 588bd669bddc..036eefbbb95f 100644
--- a/gcc/config/i386/darwin.h
+++ b/gcc/config/i386/darwin.h
@@ -308,3 +308,9 @@ along with GCC; see the file COPYING3.  If not see
 #define CLEAR_INSN_CACHE(beg, end)				\
   extern void sys_icache_invalidate(void *start, size_t len);	\
   sys_icache_invalidate ((beg), (size_t)((end)-(beg)))
+
+/* Disable custom function descriptors for Darwin when we have off-stack
+   trampolines.  */
+#undef X86_CUSTOM_FUNCTION_TEST
+#define X86_CUSTOM_FUNCTION_TEST \
+  (flag_trampolines && flag_trampoline_impl == TRAMPOLINE_IMPL_HEAP) ? 0 : 1
diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
index 641e76803355..f4772e0cb698 100644
--- a/gcc/config/i386/i386.cc
+++ b/gcc/config/i386/i386.cc
@@ -26287,7 +26287,7 @@ ix86_libgcc_floating_mode_supported_p
 #define TARGET_HARD_REGNO_SCRATCH_OK ix86_hard_regno_scratch_ok
 
 #undef TARGET_CUSTOM_FUNCTION_DESCRIPTORS
-#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS 1
+#define TARGET_CUSTOM_FUNCTION_DESCRIPTORS X86_CUSTOM_FUNCTION_TEST
 
 #undef TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID
 #define TARGET_ADDR_SPACE_ZERO_ADDRESS_VALID ix86_addr_space_zero_address_valid
diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index 4dd26e35a3e8..7e66fa095855 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -760,6 +760,12 @@ extern const char *host_detect_local_cpu (int argc, const char **argv);
 /* Minimum allocation boundary for the code of a function.  */
 #define FUNCTION_BOUNDARY 8
 
+/* We will and with this value to test if a custom function descriptor needs
+   a static chain.  The function boundary must the adjusted so that the bit
+   this represents is no longer part of the address.  0 Disables the custom
+   function descriptors.  */
+#define X86_CUSTOM_FUNCTION_TEST 1
+
 /* C++ stores the virtual bit in the lowest bit of function pointers.  */
 #define TARGET_PTRMEMFUNC_VBIT_LOCATION ptrmemfunc_vbit_in_pfn