2c9970281
Denys Vlasenko
2018-04-06
Subject
i386: make stack size optimization selectable, and allow i486 insns (bswap)
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Config.in+8 -0
| @@ -518,6 +518,14 @@ config USE_PORTABLE_CODE | |
| compiler other than gcc. | |
| If you do use gcc, this option may needlessly increase code size. | |
| + | config STACK_OPTIMIZATION_386 |
| + | bool "Use -mpreferred-stack-boundary=2 on i386 arch" |
| + | default y |
| + | help |
| + | This option makes for smaller code, but some libc versions |
| + | do not work with it (they use SSE instructions without |
| + | ensuring stack alignment). |
| + | |
| comment 'Installation Options ("make install" behavior)' | |
| choice | |
arch/i386/Makefile+7 -1
| @@ -2,6 +2,12 @@ | |
| # Build system | |
| # ========================================================================== | |
| + | # Allow i486 insns (basically, bswap insn) |
| + | # Do not try to tune for 486+ (might add padding) |
| + | CFLAGS += $(call cc-option,-march=i486 -mtune=i386,) |
| + | |
| + | ifeq ($(CONFIG_STACK_OPTIMIZATION_386),y) |
| # -mpreferred-stack-boundary=2 is essential in preventing gcc 4.2.x | |
| # from aligning stack to 16 bytes. (Which is gcc's way of supporting SSE). | |
| - | CFLAGS += $(call cc-option,-march=i386 -mpreferred-stack-boundary=2,) |
| + | CFLAGS += $(call cc-option,-mpreferred-stack-boundary=2,) |
| + | endif |