Description
- if i do this with
-mavx2
#define CLOBBER_LIST "memory", "cc", "rcx", "r11", "tmm0", "tmm1", "tmm2", "tmm3", "tmm4", "tmm5", "tmm6", "tmm7", \
"zmm0", "zmm1", "zmm2", "zmm3", "zmm4", "zmm5", "zmm6", "zmm7", "zmm8", "zmm9", "zmm10", "zmm11", "zmm12", "zmm13", "zmm14", "zmm15", "zmm16", "zmm17", "zmm18", "zmm19", "zmm20", "zmm21", "zmm22", "zmm23", "zmm24", "zmm25", "zmm26", "zmm27", "zmm28", "zmm29", "zmm30", "zmm31" \
"ymm0", "ymm1", "ymm2", "ymm3", "ymm4", "ymm5", "ymm6", "ymm7", "ymm8", "ymm9", "ymm10", "ymm11", "ymm12", "ymm13", "ymm14", "ymm15", "ymm16", "ymm17", "ymm18", "ymm19", "ymm20", "ymm21", "ymm22", "ymm23", "ymm24", "ymm25", "ymm26", "ymm27", "ymm28", "ymm29", "ymm30", "ymm31", \
"xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7", "xmm8", "xmm9", "xmm10", "xmm11", "xmm12", "xmm13", "xmm14", "xmm15", "xmm16", "xmm17", "xmm18", "xmm19", "xmm20", "xmm21", "xmm22", "xmm23", "xmm24", "xmm25", "xmm26", "xmm27", "xmm28", "xmm29", "xmm30", "xmm31",exe size increase by 2kb. all non-inlined functions that has syscall instructions push xmm6-15 on stack at beginning of function, pop them at the end of function. no random silent bugs
- if i do this with
-mavx2
#define CLOBBER_LIST "memory", "cc", "rcx", "r11", "tmm0", "tmm1", "tmm2", "tmm3", "tmm4", "tmm5", "tmm6", "tmm7", \
"ymm0", "ymm1", "ymm2", "ymm3", "ymm4", "ymm5", \
"xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5"no change to exe size. no random silent bugs
- if i do this with
-mavx2
#define CLOBBER_LIST "memory", "cc", "rcx", "r11", "tmm0", "tmm1", "tmm2", "tmm3", "tmm4", "tmm5", "tmm6", "tmm7"no change to exe size. but i get a bunch of random silent bugs at code next to syscall instruction. i dont have minimum reproducible examples, slight changes to code the bug is gone, pain to debug
according to msdn
https://learn.microsoft.com/en-us/cpp/build/x64-calling-convention?view=msvc-170#callercallee-saved-registers
https://learn.microsoft.com/en-us/cpp/build/x64-software-conventions?view=msvc-170#register-volatility-and-preservation
The x64 ABI considers the registers RAX, RCX, RDX, R8, R9, R10, R11, and XMM0-XMM5 volatile. When present, the upper portions of YMM0-YMM15 and ZMM0-ZMM15 are also volatile. On AVX512VL, the ZMM, YMM, and XMM registers 16-31 are also volatile. When AMX support is present, the TMM tile registers are volatile. Consider volatile registers destroyed on function calls unless otherwise safety-provable by analysis such as whole program optimization.
The x64 ABI considers registers RBX, RBP, RDI, RSI, RSP, R12, R13, R14, R15, and XMM6-XMM15 nonvolatile. They must be saved and restored by a function that uses them.
so my question is. how do i make the perfect bug free future proof clobber list with this? how do i clobber only upper half of a register? (also i might try -mavx512vf if i some day get a new cpu that support avx512)