[PATCH v7 01/34] Add and restructure function declaration macros

[Daniel Engel <gnu@danielengel.com>]

Most of these changes support subsequent patches in this series.
Particularly, the FUNC_START macro becomes part of a new macro chain:

  * FUNC_ENTRY              Common global symbol directives
  * FUNC_START_SECTION      FUNC_ENTRY to start a new <section>
  * FUNC_START              FUNC_START_SECTION <".text">

The effective definition of FUNC_START is unchanged from the previous
version of lib1funcs.  See code comments for detailed usage.

The new names FUNC_ENTRY and FUNC_START_SECTION were chosen specifically
to complement the existing FUNC_START name.  Alternate name patterns are
possible (such as {FUNC_SYMBOL, FUNC_START_SECTION, FUNC_START_TEXT}),
but any change to FUNC_START would require refactoring much of libgcc.

Additionally, a parallel chain of new macros supports weak functions:

  * WEAK_ENTRY
  * WEAK_START_SECTION
  * WEAK_START
  * WEAK_ALIAS

Moving the CFI_* macros earlier in the file scope will increase their
scope for use in additional functions.

gcc/libgcc/ChangeLog:
2022-10-09 Daniel Engel <gnu@danielengel.com>

	* config/arm/lib1funcs.S:
	(LLSYM): New macro prefix ".L" for strippable local symbols.
	(CFI_START_FUNCTION, CFI_END_FUNCTION): Moved earlier in the file.
	(FUNC_ENTRY): New macro for symbols with no ".section" directive.
	(WEAK_ENTRY): New macro FUNC_ENTRY + ".weak".
	(FUNC_START_SECTION): New macro FUNC_ENTRY with <section> argument.
	(WEAK_START_SECTION): New macro FUNC_START_SECTION + ".weak".
	(FUNC_START): Redefined in terms of FUNC_START_SECTION <".text">.
	(WEAK_START): New macro FUNC_START + ".weak".
	(WEAK_ALIAS): New macro FUNC_ALIAS + ".weak".
	(FUNC_END): Moved after FUNC_START macro group.
	(THUMB_FUNC_START): Moved near the other *FUNC* macros.
	(THUMB_SYNTAX, ARM_SYM_START, SYM_END): Deleted unused macros.
---
 libgcc/config/arm/lib1funcs.S | 109 +++++++++++++++++++++-------------
 1 file changed, 69 insertions(+), 40 deletions(-)

diff --git a/libgcc/config/arm/lib1funcs.S b/libgcc/config/arm/lib1funcs.S
index 8c39c9f20a2..a4fa62b3832 100644
--- a/libgcc/config/arm/lib1funcs.S
+++ b/libgcc/config/arm/lib1funcs.S
@@ -69,11 +69,13 @@ see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 #define TYPE(x) .type SYM(x),function
 #define SIZE(x) .size SYM(x), . - SYM(x)
 #define LSYM(x) .x
+#define LLSYM(x) .L##x
 #else
 #define __PLT__
 #define TYPE(x)
 #define SIZE(x)
 #define LSYM(x) x
+#define LLSYM(x) x
 #endif
 
 /* Function end macros.  Variants for interworking.  */
@@ -182,6 +184,16 @@ LSYM(Lend_fde):
 #endif
 .endm
 
+.macro CFI_START_FUNCTION
+	.cfi_startproc
+	.cfi_remember_state
+.endm
+
+.macro CFI_END_FUNCTION
+	.cfi_restore_state
+	.cfi_endproc
+.endm
+
 /* Don't pass dirn, it's there just to get token pasting right.  */
 
 .macro	RETLDM	regs=, cond=, unwind=, dirn=ia
@@ -324,10 +336,6 @@ LSYM(Lend_fde):
 .endm
 #endif
 
-.macro FUNC_END name
-	SIZE (__\name)
-.endm
-
 .macro DIV_FUNC_END name signed
 	cfi_start	__\name, LSYM(Lend_div0)
 LSYM(Ldiv0):
@@ -340,48 +348,76 @@ LSYM(Ldiv0):
 	FUNC_END \name
 .endm
 
-.macro THUMB_FUNC_START name
-	.globl	SYM (\name)
-	TYPE	(\name)
-	.thumb_func
-SYM (\name):
-.endm
-
 /* Function start macros.  Variants for ARM and Thumb.  */
 
 #ifdef __thumb__
 #define THUMB_FUNC .thumb_func
 #define THUMB_CODE .force_thumb
-# if defined(__thumb2__)
-#define THUMB_SYNTAX
-# else
-#define THUMB_SYNTAX
-# endif
 #else
 #define THUMB_FUNC
 #define THUMB_CODE
-#define THUMB_SYNTAX
 #endif
 
+.macro THUMB_FUNC_START name
+	.globl  SYM (\name)
+	TYPE    (\name)
+	.thumb_func
+SYM (\name):
+.endm
+
+/* Strong global symbol, ".text" section.
+   The default macro for function declarations. */
 .macro FUNC_START name
-	.text
+	FUNC_START_SECTION \name .text
+.endm
+
+/* Weak global symbol, ".text" section.
+   Use WEAK_* macros to declare a function/object that may be discarded in by
+    the linker when another library or object exports the same name.
+   Typically, functions declared with WEAK_* macros implement a subset of
+    functionality provided by the overriding definition, and are discarded
+    when the full functionality is required. */
+.macro WEAK_START name
+	.weak SYM(__\name)
+	FUNC_START_SECTION \name .text
+.endm
+
+/* Strong global symbol, alternate section.
+   Use the *_START_SECTION macros for declarations that the linker should
+    place in a non-defailt section (e.g. ".rodata", ".text.subsection"). */
+.macro FUNC_START_SECTION name section
+	.section \section,"x"
+	.align 0
+	FUNC_ENTRY \name
+.endm
+
+/* Weak global symbol, alternate section. */
+.macro WEAK_START_SECTION name section
+	.weak SYM(__\name)
+	FUNC_START_SECTION \name \section
+.endm
+
+/* Strong global symbol.
+   Use *_ENTRY macros internal to a function/object body to declare a second
+    or subsequent entry point without changing the assembler state.
+   Because there is no alignment specification, these macros should never
+    replace the *_START_* macros as the first declaration in any object. */
+.macro FUNC_ENTRY name
 	.globl SYM (__\name)
 	TYPE (__\name)
-	.align 0
 	THUMB_CODE
 	THUMB_FUNC
-	THUMB_SYNTAX
 SYM (__\name):
 .endm
 
-.macro ARM_SYM_START name
-       TYPE (\name)
-       .align 0
-SYM (\name):
+/* Weak global symbol. */
+.macro WEAK_ENTRY name
+	.weak SYM(__\name)
+	FUNC_ENTRY \name
 .endm
 
-.macro SYM_END name
-       SIZE (\name)
+.macro FUNC_END name
+	SIZE (__\name)
 .endm
 
 /* Special function that will always be coded in ARM assembly, even if
@@ -447,6 +483,11 @@ SYM (__\name):
 #endif
 .endm
 
+.macro WEAK_ALIAS new old
+	.weak SYM(__\new)
+	FUNC_ALIAS \new \old
+.endm
+
 #ifndef NOT_ISA_TARGET_32BIT
 .macro	ARM_FUNC_ALIAS new old
 	.globl	SYM (__\new)
@@ -1459,10 +1500,8 @@ LSYM(Lover12):
 #ifdef L_dvmd_tls
 
 #ifdef __ARM_EABI__
-	WEAK aeabi_idiv0
-	WEAK aeabi_ldiv0
-	FUNC_START aeabi_idiv0
-	FUNC_START aeabi_ldiv0
+	WEAK_START aeabi_idiv0
+	WEAK_START aeabi_ldiv0
 	RET
 	FUNC_END aeabi_ldiv0
 	FUNC_END aeabi_idiv0
@@ -2170,16 +2209,6 @@ LSYM(Lchange_\register):
 
 #endif /* Arch supports thumb.  */
 
-.macro CFI_START_FUNCTION
-	.cfi_startproc
-	.cfi_remember_state
-.endm
-
-.macro CFI_END_FUNCTION
-	.cfi_restore_state
-	.cfi_endproc
-.endm
-
 #ifndef __symbian__
 /* The condition here must match the one in gcc/config/arm/elf.h and
    libgcc/config/arm/t-elf.  */
-- 
2.34.1