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This patch improves code generated for extension from SI to DI mode for core registers when neon is not enabled. Currently, if neon is enabled, extendsidi for core registers benefits from the patch described here (r194558 from 17 Dec 2012): http://gcc.gnu.org/ml/gcc-patches/2012-11/msg00984.html Before r194558, the compiler used to split extendsidi before register allocation (at split1 pass), which resulted in some cases in an extra register being used and an extra register move. After r194558, if neon is enabled, extendsidi is split after reload, generating better code. Unfortunately, when neon is not enabled, the splitter is still triggered before reload. For example, $ cat negdi-1.c signed long long extendsidi_negsi (signed int x) { return -x; } $ arm-none-eabi-gcc negdi-1.c -S -O2 -o- -mfpu=vfpv4 extendsidi_negsi: rsb r3, r0, #0 @ 6 *arm_negsi2 [length = 4] mov r0, r3 @ 19 *arm_movsi_vfp/1 [length = 4] mov r1, r3, asr #31 @ 20 *arm_shiftsi3 [length = 4] bx lr @ 25 *arm_return [length = 12] $ arm-none-eabi-gcc negdi-1.c -S -O2 -o- -mfpu=neon extendsidi_negsi: rsb r0, r0, #0 @ 6 *arm_negsi2 [length = 4] mov r1, r0, asr #31 @ 20 *arm_shiftsi3 [length = 4] bx lr @ 23 *arm_return [length = 12] This patch changes the condition of splitters for extendsidi to trigger only after reload. In addition, this patch fixes a bug in zero_extend<mode>di2 and extend<mode>di2 patterns. One of the alternatives in these patterns has a constraint 'w' which is not valid when neon is disabled, but the patterns don't have attributes to guard these alternatives by neon availability. This might cause an ICE when neon is not available. Currently, it seems that the patterns are only matched by RTL insns that are generated by splitters with conditions on neon being enabled. However, it may be a latent bug. In any case, the change in conditions of these splitters made by this patch triggers the bug and causes an ICE. No regression on qemu for arm-none-eabi cortex-a15 arm/thumb neon/vfpv4 softfp/soft. Bootstrap successful on Cortex-A15. I haven't added a test case because tests that scan assembly for 'mov' are very unstable. Ok for trunk? Thanks, Greta gcc/ 2013-02-21 Greta Yorsh <Greta.Yorsh@arm.com> * config/arm/arm.md (split for extendsidi): Update condition. (zero_extend<mode>di2,extend<mode>di2): Add an alternative. * config/arm/iterators.md (qhs_extenddi_cstr): Likewise. (qhs_zextenddi_cstr): Likewise.
Attachment:
extendsidi-split-cond.v2.patch.txt
Description: Text document
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