longlong.h for RISCV should define count_leading_zeros and count_trailing_zeros and COUNT_LEADING_ZEROS_0 when ZBB is enabled.
The following patch patch fixes the bug reported in, https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110181 The divdi3 on riscv32 with zbb extension generates __clz_tab instead of genearating __builtin_clzll/__builtin_clz which is not efficient since lookup table is emitted. Updating longlong.h to use this __builtin_clzll/__builtin_clz generates optimized code for the instruction. gcc/include/ChangeLog * longlong.h [__riscv] (count_leading_zeros): Define. [__riscv] (count_trailing_zeros): Likewise. [__riscv] (COUNT_LEADING_ZEROS_0): Likewise. diff --git a/include/longlong.h b/include/longlong.h index b5dec95b7ed..de737586180 100644 --- a/include/longlong.h +++ b/include/longlong.h @@ -1065,6 +1065,18 @@ extern UDItype __umulsidi3 (USItype, USItype); #endif #if defined(__riscv) +#ifdef __riscv_zbb +#if W_TYPE_SIZE == 32 +#define count_leading_zeros(COUNT, X) ((COUNT) = __builtin_clz (X)) +#define count_trailing_zeros(COUNT, X) ((COUNT) = __builtin_ctz (X)) +#define COUNT_LEADING_ZEROS_0 32 +#endif /* W_TYPE_SIZE == 32 */ +#if W_TYPE_SIZE == 64 +#define count_leading_zeros(COUNT, X) ((COUNT) = __builtin_clzll (X)) +#define count_trailing_zeros(COUNT, X) ((COUNT) = __builtin_ctzll (X)) +#define COUNT_LEADING_ZEROS_0 64 +#endif /* W_TYPE_SIZE == 64 */ +#endif /* __riscv_zbb */ #ifdef __riscv_mul #define __umulsidi3(u,v) ((UDWtype)(UWtype)(u) * (UWtype)(v)) #define __muluw3(a, b) ((UWtype)(a) * (UWtype)(b)) -- 2.43.0 The above patch updates libgcc library, so the change can be visualized only through full disassembly for a testcase. The existing gcc regression test suite for riscv cannot be used to check this code generation, change as-is. Hence no testcase is added as part of the patch. Please suggest a way to add a visual testcase and confirm the changes in the code generation.
