Ping?
> -----Original Message-----
> From: Tony Wang [mailto:tony.w...@arm.com]
> Sent: Thursday, August 21, 2014 2:15 PM
> To: 'gcc-patches@gcc.gnu.org'
> Subject: [PATCH 1/3,ARM,libgcc]Code size optimization for the fmul/fdiv and
> dmul/ddiv function in libgcc
>
> Hi there,
>
> In libgcc the file ieee754-sf.S and ieee754-df.S have some function pairs
> which will be bundled into one .o
file and
> sharing the same .text section. For example, the fmul and fdiv, the libgcc
> makefile will build them into one
.o file
> and archived into libgcc.a. So when user only call single float point
> multiply functions, the fdiv function
will also be
> linked, and as fmul and fdiv share the same .text section, linker option
> --gc-sections or -flot can't remove
the
> dead code.
>
> So this optimization just separates the function pair(fmul/fdiv and
> dmul/ddiv) into different sections,
following
> the naming pattern of -ffunction-sections(.text.__functionname), through
> which the unused sections of
> fdiv/ddiv can be eliminated through option --gcc-sections when users only use
> fmul/dmul.The solution is to
add
> a conditional statement in the macro FUNC_START, which will conditional
> change the section of a function
> from .text to .text.__\name. when compiling with the L_arm_muldivsf3 or
> L_arm_muldivdf3 macro.
>
> GCC regression test has been done on QEMU for Cortex-M3. No new regressions
> when turn on this patch.
>
> The code reduction for thumb2 on cortex-m3 is:
> 1. When user only use single float point multiply:
> fmul+fdiv => fmul will have a code size reduction of 318 bytes.
>
> 2. When user only use double float point multiply:
> dmul+ddiv => dmul will have a code size reduction of 474 bytes.
>
> Ok for trunk?
>
> BR,
> Tony
>
> Step 1: Provide another option: sp-scetion to control whether to split the
> section of a function pair into
two part.
>
> gcc/libgcc/ChangeLog:
> 2014-08-21 Tony Wang <tony.w...@arm.com>
>
> * config/arm/lib1funcs.S (FUNC_START): Add conditional section
> redefine for macro L_arm_muldivsf3 and L_arm_muldivdf3
> (SYM_END, ARM_SYM_START): Add macros used to expose function
> Symbols
>
> diff --git a/libgcc/config/arm/lib1funcs.S b/libgcc/config/arm/lib1funcs.S
> index b617137..0f87111 100644
> --- a/libgcc/config/arm/lib1funcs.S
> +++ b/libgcc/config/arm/lib1funcs.S
> @@ -418,8 +418,12 @@ SYM (\name):
> #define THUMB_SYNTAX
> #endif
>
> -.macro FUNC_START name
> +.macro FUNC_START name sp_section=
> + .ifc \sp_section, function_section
> + .section .text.__\name,"ax",%progbits
> + .else
> .text
> + .endif
> .globl SYM (__\name)
> TYPE (__\name)
> .align 0
> @@ -429,14 +433,24 @@ SYM (\name):
> SYM (__\name):
> .endm
>
> +.macro ARM_SYM_START name
> + TYPE (\name)
> + .align 0
> +SYM (\name):
> +.endm
> +
> +.macro SYM_END name
> + SIZE (\name)
> +.endm
> +
> /* Special function that will always be coded in ARM assembly, even if
> in Thumb-only compilation. */
>
> #if defined(__thumb2__)
>
> /* For Thumb-2 we build everything in thumb mode. */
> -.macro ARM_FUNC_START name
> - FUNC_START \name
> +.macro ARM_FUNC_START name sp_section=
> + FUNC_START \name \sp_section
> .syntax unified
> .endm
> #define EQUIV .thumb_set
> @@ -467,8 +481,12 @@ _L__\name:
> #ifdef __ARM_ARCH_6M__
> #define EQUIV .thumb_set
> #else
> -.macro ARM_FUNC_START name
> +.macro ARM_FUNC_START name sp_section=
> + .ifc \sp_section, function_section
> + .section .text.__\name,"ax",%progbits
> + .else
> .text
> + .endif
> .globl SYM (__\name)
> TYPE (__\name)
> .align 0
