busybox/arch/i386/Makefile

# ==========================================================================
# 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,-mpreferred-stack-boundary=2,)
endif

# "Control how GCC aligns variables.
# Supported values for type are compat uses increased alignment value
# compatible uses GCC 4.8 and earlier, abi uses alignment value as specified by the psABI,
# and cacheline uses increased alignment value to match the cache line size.
# compat is the default."
# "abi" seems to be somewhat successful in preventing oversealous data alignment.
CFLAGS += $(call cc-option,-malign-data=abi,)
build system: fix for non-i386 builds 2006-10-10 01:17:38 +05:30			`# ==========================================================================`
			`# Build system`
			`# ==========================================================================`

i386: make stack size optimization selectable, and allow i486 insns (bswap) It's hard to imagine someone still using non-bswap equipped CPU function old new delta xmalloc_optname_optval 888 879 -9 write_leases 214 205 -9 write32 36 27 -9 update_status 612 603 -9 udhcpd_main 1468 1459 -9 udhcpc_main 2708 2699 -9 udhcp_run_script 804 795 -9 sha256_process_block64 423 414 -9 sha1_process_block64 337 328 -9 sha1_end 80 71 -9 send_ACK 161 152 -9 select_lease_time 64 55 -9 rpm_getint 118 109 -9 readprofile_main 1719 1710 -9 read32 33 24 -9 rdate_main 236 227 -9 machtime 39 30 -9 inet_addr_match 103 94 -9 get_prefix 344 335 -9 f_write32 31 22 -9 f_read32 31 22 -9 dumpleases_main 620 611 -9 KeyExpansion 197 188 -9 udhcp_str2optset 536 518 -18 read_config 222 204 -18 lfp_to_d 55 37 -18 ipaddr_modify 1226 1208 -18 dnsd_main 1278 1260 -18 des_crypt 1344 1326 -18 d_to_lfp 106 88 -18 bb_bswap_64 29 11 -18 INET_setroute 827 809 -18 read_leases 330 309 -21 zcip_main 1256 1229 -27 send_offer 476 449 -27 ipcalc_main 534 507 -27 handle_incoming_and_exit 2821 2794 -27 fmt_time_bernstein_25 131 104 -27 common_traceroute_main 3804 3768 -36 rpm_gettags 451 397 -54 parse_args 1412 1358 -54 volume_id_probe_hfs_hfsplus 627 564 -63 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 0/42 up/down: 0/-732) Total: -732 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com> 2018-04-06 22:25:35 +05:30			`# 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)`
add comment why preferred stack boundary is 4 on i386 2007-07-24 02:35:06 +05:30			`# -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).`
i386: make stack size optimization selectable, and allow i486 insns (bswap) It's hard to imagine someone still using non-bswap equipped CPU function old new delta xmalloc_optname_optval 888 879 -9 write_leases 214 205 -9 write32 36 27 -9 update_status 612 603 -9 udhcpd_main 1468 1459 -9 udhcpc_main 2708 2699 -9 udhcp_run_script 804 795 -9 sha256_process_block64 423 414 -9 sha1_process_block64 337 328 -9 sha1_end 80 71 -9 send_ACK 161 152 -9 select_lease_time 64 55 -9 rpm_getint 118 109 -9 readprofile_main 1719 1710 -9 read32 33 24 -9 rdate_main 236 227 -9 machtime 39 30 -9 inet_addr_match 103 94 -9 get_prefix 344 335 -9 f_write32 31 22 -9 f_read32 31 22 -9 dumpleases_main 620 611 -9 KeyExpansion 197 188 -9 udhcp_str2optset 536 518 -18 read_config 222 204 -18 lfp_to_d 55 37 -18 ipaddr_modify 1226 1208 -18 dnsd_main 1278 1260 -18 des_crypt 1344 1326 -18 d_to_lfp 106 88 -18 bb_bswap_64 29 11 -18 INET_setroute 827 809 -18 read_leases 330 309 -21 zcip_main 1256 1229 -27 send_offer 476 449 -27 ipcalc_main 534 507 -27 handle_incoming_and_exit 2821 2794 -27 fmt_time_bernstein_25 131 104 -27 common_traceroute_main 3804 3768 -36 rpm_gettags 451 397 -54 parse_args 1412 1358 -54 volume_id_probe_hfs_hfsplus 627 564 -63 ------------------------------------------------------------------------------ (add/remove: 0/0 grow/shrink: 0/42 up/down: 0/-732) Total: -732 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com> 2018-04-06 22:25:35 +05:30			`CFLAGS += $(call cc-option,-mpreferred-stack-boundary=2,)`
			`endif`
build system: combat gcc zealotry in data alignment text data bss dec hex filename 1020934 559 5052 1026545 fa9f1 busybox_old 1020750 559 5052 1026361 fa939 busybox_unstripped Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com> 2020-12-14 10:23:45 +05:30
			`# "Control how GCC aligns variables.`
			`# Supported values for type are compat uses increased alignment value`
			`# compatible uses GCC 4.8 and earlier, abi uses alignment value as specified by the psABI,`
			`# and cacheline uses increased alignment value to match the cache line size.`
			`# compat is the default."`
			`# "abi" seems to be somewhat successful in preventing oversealous data alignment.`
			`CFLAGS += $(call cc-option,-malign-data=abi,)`