在 2024/2/7 上午12:23, Xi Ruoyao 写道:
Hi Lulu, I'm proposing to backport r14-4674 "LoongArch: Delete macro definition ASM_OUTPUT_ALIGN_WITH_NOP." to releases/gcc-12 and releases/gcc-13. The reasons: 1. Strictly speaking, the old ASM_OUTPUT_ALIGN_WITH_NOP macro may cause a correctness issue. For example, a developer may use -falign- functions=16 and then use the low 4 bits of a function pointer to encode some metainfo. Then ASM_OUTPUT_ALIGN_WITH_NOP causes the functions not really aligned to a 16 bytes boundary, causing some breakage. 2. With Binutils-2.42, ASM_OUTPUT_ALIGN_WITH_NOP can cause illegal opcodes. For example: .globl _start _start: .balign 32 nop nop nop addi.d $a0, $r0, 1 .balign 16,54525952,4 addi.d $a0, $a0, 1 is assembled and linked to: 0000000000000220 <_start>: 220: 03400000 nop 224: 03400000 nop 228: 03400000 nop 22c: 02c00404 li.d $a0, 1 230: 00000000 .word 0x00000000 # <== OOPS! 234: 02c00484 addi.d $a0, $a0, 1 Arguably this is a bug in GAS (it should at least error out for the unsupported case where .balign 16,54525952,4 appears with -mrelax; I'd prefer it to support the 3-operand .align directive even -mrelax for reasons I've given in [1]). But we can at least work it around by removing ASM_OUTPUT_ALIGN_WITH_NOP to allow using GCC 13.3 with Binutils 2.42. 3. Without ASM_OUTPUT_ALIGN_WITH_NOP, GCC just outputs something like ".align 5" which works as expected since Binutils-2.38. 4. GCC < 14 does not have a default setting of -falign-*, so changing this won't affect anyone who do not specify -falign-* explicitly. [1]:https://github.com/loongson-community/discussions/issues/41#issuecomment-1925872603 Is it OK to backport r14-4674 into releases/gcc-12 and releases/gcc-13 then?
Ok, I agree with you. Thanks!
