MSP430: Remove .init/.fini sections

The .init/.fini sections are not required for msp430-elf, and add unnecessary
code bloat to the CRT library. These sections are specified as "unused" by
the MSP430 EABI.

.init existed to call __crt0_run_{init,preinit}_array which run through
the functions in .{init,preinit}_array.
__crt0_run_{init,preinit}_array are already dynamically included like the
other crt0 functions, so these can be placed before the call to main,
which ensures they are still called if needed.
With these functions moved, .init has no purpose and can be removed.

.fini existed to call __crt0_run_fini_array.
However, the "__msp430_fini" symbol which marks the start of .fini has
never been used, so no termination routines have ever been run for
msp430. On returning from main(), _exit() is called which just loops
forever.
So there is no current expectation that __crt0_run_fini_array will
get called by the CRT code. Further work is to ensure functions
registered with atexit can be optionally called during program termination,
and then __crt0_run_fini_array can be registered with atexit during
program initialization.

The mechanisms for supporting the "-minrt" option have also been removed.
"-minrt" enabled a "minimum runtime environment" by removing calls to
functions which run global static initializers and constructors. Since
this behaviour is now dynamic, and these functions are only included
when needed, the minrt versions of the CRT object files are no longer
required.

1 files changed, 61 insertions, 104 deletions

diff --git a/libgloss/msp430/crt0.S b/libgloss/msp430/crt0.S
index 42464ddbe..88876cd48 100644
--- a/libgloss/msp430/crt0.S
+++ b/libgloss/msp430/crt0.S
@@ -52,28 +52,25 @@ __msp430_resetvec_hook:
 
 START_CRT_FUNC 0000 start
 	.refsym	__msp430_resetvec_hook
-#ifdef MINRT
-	.refsym	__crt0_call_just_main
-#else
-	.refsym	__crt0_call_init_then_main
-#endif
+	.refsym	__crt0_call_main
 	mov_	#__stack, R1
 
 END_CRT_FUNC	start
 #endif
 
-;; Some of the CRT functions below will only be present in the final linked
-;; executable if the assembler decides they are needed.  It will only define
-;; the symbol necessary to prevent them being garbage collected by the linker
-;; if the file being assembled has a specific section.
-;; The CRT functions this applies to are:
-;; init_bss, movedata, move_highdata, init_highbss, run_init_array,
-;; run_preinit_array, run_fini_array and run_array.
+;; The CRT functions below will only be present in the final linked
+;; executable if the assembler decides they are needed.  The assembler will
+;; only define the symbol necessary to prevent them being garbage collected
+;; by the linker if the file being assembled has a specific section,
+;; or some other criteria is met.
+;; The exception to this is __crt0_call_exit. GCC will include this function
+;; if it detects that main() has an epilogue. For example, if main() has a
+;; while(1) loop at the end, GCC will not generate an epilogue (since it won't
+;; return) and __crt0_call_exit won't be included.
 
 #if Lbss
-;; Note - this section is only included in the startup code of the
-;; application if it is needed.  It is responsible for initializing
-;; the contents of the .bss section.
+;; This function is responsible for initializing the contents of the
+;; .bss section.
 
 START_CRT_FUNC 0100 init_bss
 
@@ -91,9 +88,8 @@ END_CRT_FUNC	init_bss
 
 #ifdef __MSP430X_LARGE__
 #if Lhigh_bss
-;; Note - this section is only included in the startup code of the
-;; application if it is needed.  It is responsible for initializing
-;; the contents of the .upper.bss section.
+;; This function is responsible for initializing the contents of the
+;; .upper.bss section.
 
 START_CRT_FUNC 0200 init_highbss
 	
@@ -112,8 +108,7 @@ END_CRT_FUNC	init_highbss
 
 
 #if Lmovedata
-;; Note - this section is only included in the startup code of the
-;; application if it is needed.  It is responsible for copying the
+;; This function is responsible for copying the
 ;; contents of the .data section from its load address (in ROM) to
 ;; its run-time address (in RAM).
 
@@ -136,8 +131,7 @@ END_CRT_FUNC	movedata
 
 #ifdef __MSP430X_LARGE__
 #if Lmove_highdata
-;; Note - this section is only included in the startup code of the application
-;; if it is needed.  It is responsible either for making sure that the
+;; This function is responsible for making sure that the
 ;; contents of the .upper.data section have their correct startup values.
 ;; If a copy of the .upper.data section is stored in ROM then this means
 ;; copying the contents into HIFRAM.  If a copy of .upper.data is stored in a
@@ -175,44 +169,62 @@ END_CRT_FUNC	move_highdata
 #endif /* Lmove_highdata */
 #endif /* __MSP430X_LARGE__ */
 
+#if Lrun_preinit_array
+;; This function is responsible for setting up the arguments
+;; required for __crt0_run_array, to run the functions in .preinit_array.
+START_CRT_FUNC 0500 run_preinit_array
+
+	mov_	#__preinit_array_start, R4
+	mov_	#__preinit_array_end, R5
+	mov_	#PTRsz, R6
+	call_	#__crt0_run_array
 
-#if Lmain_minrt
-;; Note - this section is only included in the startup code of the
-;; application if it is needed.  It is responsible for just calling
-;; main.  No initialization code is called first, and main is not
-;; expected to return.
+END_CRT_FUNC	run_preinit_array
+#endif /* Lrun_preinit_array */
 
-START_CRT_FUNC 0600 call_just_main
+#if Lrun_init_array
+;; This function is responsible for setting up the arguments
+;; required for __crt0_run_array, to run the functions in .init_array.
+START_CRT_FUNC 0600 run_init_array
 
-	clr.w	R12		; Set argc == 0
-	call_	#main
-END_CRT_FUNC	call_just_main
-#endif /* Lmain_minrt */
+	mov_	#__init_array_start, R4
+	mov_	#__init_array_end, R5
+	mov_	#PTRsz, R6
+	call_	#__crt0_run_array
 
+END_CRT_FUNC	run_init_array
+#endif /* Lrun_init_array */
 
-#if Lmain
-;; Note - this section is only included in the startup code of the
-;; application if it is needed.  It is responsible for calling the
-;; initialization code - constructors, etc - and then main.  If main
-;; returns then the following section should be present to catch it.
+;; FIXME: There are currently no program termination routines executed for
+;; msp430.
+#if 0
+#if Lrun_fini_array
+;; Ensure global C++ destructors in .fini_array are called on exit
+;; by registering __crt0_run_fini_array with atexit.
+START_CRT_FUNC 0700 register_fini_array
+
+	mov_	#__crt0_run_fini_array, R12
+	call_	#atexit
+
+END_CRT_FUNC	register_fini_array
+#endif /* Lrun_fini_array */
+#endif /* 0 */
 
-START_CRT_FUNC 0700 call_init_then_main
+#if Lmain
+;; This function is always included and calls main().
 
-	call_	#__msp430_init
+START_CRT_FUNC 0800 call_main
 
 	clr.w	R12		; Set argc == 0
 	call_	#main
 
-END_CRT_FUNC	call_init_then_main
+END_CRT_FUNC	call_main
 #endif /* Lmain */
 
-
 #if Lcallexit
-;; Note - this section is only included in the startup code of the
-;; application if it is needed.  It is responsible for calling exit
-;; once main has finished.
+;; This function is responsible for calling exit once main has finished.
 
-START_CRT_FUNC 0800 call_exit
+START_CRT_FUNC 0900 call_exit
 
 	call_	#_exit
 
@@ -221,46 +233,15 @@ END_CRT_FUNC	call_exit
 
 ;----------------------------------------
 
-#ifndef MINRT
-
-#if Lrun_preinit_array
-;; Note - this section is only included in the startup code of the application
-;; if it is needed.  It is responsible for setting up the arguments
-;; required for __crt0_run_array, to run the functions in .preinit_array.
-START_CRT_FUNC 0910 run_preinit_array
-
-	mov_	#__preinit_array_start, R4
-	mov_	#__preinit_array_end, R5
-	mov_	#PTRsz, R6
-	br_	#__crt0_run_array
-
-END_CRT_FUNC	run_preinit_array
-#endif /* Lrun_preinit_array */
-
-#if Lrun_init_array
-;; Note - this section is only included in the startup code of the application
-;; if it is needed.  It is responsible for setting up the arguments
-;; required for __crt0_run_array, to run the functions in .init_array.
-START_CRT_FUNC 0920 run_init_array
-
-	mov_	#__init_array_start, R4
-	mov_	#__init_array_end, R5
-	mov_	#PTRsz, R6
-	br_	#__crt0_run_array
-
-END_CRT_FUNC	run_init_array
-#endif /* Lrun_init_array */
-
 #if Lrun_fini_array
-;; Note - this section is only included in the startup code of the application
-;; if it is needed.  It is responsible for setting up the arguments
+;; This function is responsible for setting up the arguments
 ;; required for __crt0_run_array, to run the functions in .fini_array.
-START_CRT_FUNC 0930 run_fini_array
+START_CRT_FUNC 1000 run_fini_array
 
 	mov_	#__fini_array_start, R4
 	mov_	#__fini_array_end, R5
 	mov_	#-PTRsz, R6
-	br_	#__crt0_run_array
+	call_	#__crt0_run_array
 
 END_CRT_FUNC	run_fini_array
 #endif /* Lrun_fini_array */
@@ -268,7 +249,7 @@ END_CRT_FUNC	run_fini_array
 #if Lrun_array
 ;; Note - this section is only included in the startup code of the application
 ;; if it is needed by one of the above run_*_array functions.
-START_CRT_FUNC 0980 run_array
+START_CRT_FUNC 1100 run_array
 
 	cmp_	R4, R5
 	jeq	_msp430_run_done
@@ -282,27 +263,3 @@ END_CRT_FUNC	run_array
 _msp430_run_done:
 	ret_
 #endif /* Lrun_array */
-
-;----------------------------------------
-#if L0
-
-	.section	.init,"ax"
-
-	.global __msp430_init
-__msp430_init:
-
-	.section	.fini,"ax"
-
-	.global __msp430_fini
-__msp430_fini:
-	call_	#__crt0_run_fini_array
-	
-;; If this function is not defined externally, we don't need it to do
-;; anything.
-	.text
-	.weak __crt0_run_fini_array
-__crt0_run_fini_array:
-	ret_
-
-#endif
-#endif /* not MINRT */