The MSP430 target does not need to support dynamic shared objects so
__cxa_atexit does not need to be used - atexit is sufficient.
Newlib atexit is a fine replacement as it also supports registration of more
than 32 functions.
By not using __cxa_atexit, we can define TARGET_LIBGCC_REMOVE_DSO_HANDLE to
remove the definition of __dso_handle from crtstuff.c, saving code size by
removing the necessity to link in functions to initialize global data in
*every* program.
>From a0086b73d0e029c8888ab2f65a91e67a2502e4d4 Mon Sep 17 00:00:00 2001
From: Jozef Lawrynowicz <joze...@mittosystems.com>
Date: Wed, 30 Oct 2019 16:39:52 +0000
Subject: [PATCH 3/4] MSP430: Disable __cxa_atexit
gcc/ChangeLog:
2019-11-07 Jozef Lawrynowicz <joze...@mittosystems.com>
* config.gcc (msp430*-*-*): Disable __cxa_atexit by default.
* config/msp430/msp430.c (msp430_option_override): Emit an error if
-fuse-cxa-atexit was used when __cxa_atexit was disabled at configure
time.
* config/msp430/msp430.h (TARGET_LIBGCC_REMOVE_DSO_HANDLE): Define if
__cxa_atexit was disabled at configure time.
gcc/testsuite/ChangeLog:
2019-11-07 Jozef Lawrynowicz <joze...@mittosystems.com>
* g++.dg/init/dso_handle1.C: Add dg-require-cxa-atexit.
* g++.dg/init/dso_handle2.C: Likewise.
* g++.dg/other/cxa-atexit1.C: Likewise.
* lib/target-supports.exp (check_cxa_atexit_available): Add hard-coded
case for msp430.
---
gcc/config.gcc | 7 +++++++
gcc/config/msp430/msp430.c | 9 +++++++++
gcc/config/msp430/msp430.h | 6 ++++++
gcc/testsuite/g++.dg/init/dso_handle1.C | 1 +
gcc/testsuite/g++.dg/init/dso_handle2.C | 1 +
gcc/testsuite/g++.dg/other/cxa-atexit1.C | 1 +
gcc/testsuite/lib/target-supports.exp | 3 +++
7 files changed, 28 insertions(+)
diff --git a/gcc/config.gcc b/gcc/config.gcc
index d74bcbb9856..2e79101cc8f 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -2533,6 +2533,13 @@ msp430*-*-*)
tmake_file="${tmake_file} msp430/t-msp430"
extra_objs="${extra_objs} msp430-devices.o"
extra_gcc_objs="driver-msp430.o msp430-devices.o"
+
+ # __cxa_atexit increases code size, and we don't need to support dynamic
+ # shared objects on MSP430, so regular Newlib atexit is a fine
+ # replacement as it also supports registration of more than 32
+ # functions.
+ default_use_cxa_atexit=no
+
# Enable .init_array unless it has been explicitly disabled.
# The MSP430 EABI mandates the use of .init_array, and the Newlib CRT
# code since mid-2019 expects it.
diff --git a/gcc/config/msp430/msp430.c b/gcc/config/msp430/msp430.c
index fe1fcc0db43..ce8d863abd3 100644
--- a/gcc/config/msp430/msp430.c
+++ b/gcc/config/msp430/msp430.c
@@ -284,6 +284,15 @@ msp430_option_override (void)
possible to build newlib with -Os enabled. Until now... */
if (TARGET_OPT_SPACE && optimize < 3)
optimize_size = 1;
+
+#if !DEFAULT_USE_CXA_ATEXIT
+ /* By default, we enforce atexit() instead of __cxa_atexit() to save on code
+ size and remove the declaration of __dso_handle from the CRT library.
+ Configuring GCC with --enable-__cxa-atexit re-enables it by defining
+ DEFAULT_USE_CXA_ATEXIT to 1. */
+ if (flag_use_cxa_atexit)
+ error ("%<-fuse-cxa-atexit%> is not supported for msp430-elf");
+#endif
}
#undef TARGET_SCALAR_MODE_SUPPORTED_P
diff --git a/gcc/config/msp430/msp430.h b/gcc/config/msp430/msp430.h
index 90ceec0e947..25944125182 100644
--- a/gcc/config/msp430/msp430.h
+++ b/gcc/config/msp430/msp430.h
@@ -509,4 +509,10 @@ typedef struct
#define ASM_OUTPUT_ALIGNED_DECL_COMMON(FILE, DECL, NAME, SIZE, ALIGN) \
msp430_output_aligned_decl_common ((FILE), (DECL), (NAME), (SIZE), (ALIGN))
+#if !DEFAULT_USE_CXA_ATEXIT
+/* We're not using __cxa_atexit, so __dso_handle isn't needed. */
+#undef TARGET_LIBGCC_REMOVE_DSO_HANDLE
+#define TARGET_LIBGCC_REMOVE_DSO_HANDLE
+#endif
+
#define SYMBOL_FLAG_LOW_MEM (SYMBOL_FLAG_MACH_DEP << 0)
diff --git a/gcc/testsuite/g++.dg/init/dso_handle1.C b/gcc/testsuite/g++.dg/init/dso_handle1.C
index 97f67cad8f4..dc92e22d12a 100644
--- a/gcc/testsuite/g++.dg/init/dso_handle1.C
+++ b/gcc/testsuite/g++.dg/init/dso_handle1.C
@@ -1,6 +1,7 @@
// PR c++/17042
// { dg-do assemble }
/* { dg-require-weak "" } */
+// { dg-require-cxa-atexit "" }
// { dg-options "-fuse-cxa-atexit" }
struct A
diff --git a/gcc/testsuite/g++.dg/init/dso_handle2.C b/gcc/testsuite/g++.dg/init/dso_handle2.C
index b219dc02611..6e151e50fa7 100644
--- a/gcc/testsuite/g++.dg/init/dso_handle2.C
+++ b/gcc/testsuite/g++.dg/init/dso_handle2.C
@@ -1,4 +1,5 @@
// PR c++/58846
+// { dg-require-cxa-atexit "" }
// { dg-options "-fuse-cxa-atexit" }
extern "C" { char* __dso_handle; }
diff --git a/gcc/testsuite/g++.dg/other/cxa-atexit1.C b/gcc/testsuite/g++.dg/other/cxa-atexit1.C
index a51f3340142..d6ab3dc4733 100644
--- a/gcc/testsuite/g++.dg/other/cxa-atexit1.C
+++ b/gcc/testsuite/g++.dg/other/cxa-atexit1.C
@@ -1,4 +1,5 @@
// { dg-do compile }
+// { dg-require-cxa-atexit "" }
// { dg-options "-O2 -fuse-cxa-atexit" }
# 1 "cxa-atexit1.C"
diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 6c836a4accc..58bedb64d42 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -2513,6 +2513,9 @@ proc check_cxa_atexit_available { } {
} elseif { [istarget *-*-vxworks] } {
# vxworks doesn't have __cxa_atexit but subsequent test passes.
expr 0
+ } elseif { [istarget msp430-*-*] } {
+ # msp430 doesn't have __cxa_atexit but subsequent test passes.
+ expr 0
} else {
check_runtime_nocache cxa_atexit_available {
// C++
--
2.17.1
