The LA464 micro-architecture is sensitive to alignment of code. The Loongson team has benchmarked various combinations of function, the results [1] show that 16-byte label alignment together with 32-byte function alignment gives best results in terms of SPEC score.
Add a mtune-based table-driven mechanism to set the default of -falign-{functions,labels}. As LA464 is the first (and the only for now) uarch supported by GCC, the same setting is also used for the "generic" -mtune=loongarch64. In the future we may set different settings for LA{2,3,6}64 once we add the support for them. Bootstrapped and regtested on loongarch64-linux-gnu. Ok for trunk? gcc/ChangeLog: * config/loongarch/loongarch-tune.h (loongarch_align): New struct. * config/loongarch/loongarch-def.h (loongarch_cpu_align): New array. * config/loongarch/loongarch-def.c (loongarch_cpu_align): Define the array. * config/loongarch/loongarch.cc (loongarch_option_override_internal): Set the value of -falign-functions= if -falign-functions is enabled but no value is given. Likewise for -falign-labels=. --- gcc/config/loongarch/loongarch-def.c | 12 ++++++++++++ gcc/config/loongarch/loongarch-def.h | 1 + gcc/config/loongarch/loongarch-tune.h | 8 ++++++++ gcc/config/loongarch/loongarch.cc | 6 ++++++ 4 files changed, 27 insertions(+) diff --git a/gcc/config/loongarch/loongarch-def.c b/gcc/config/loongarch/loongarch-def.c index fc4ebbefede..6729c857f7c 100644 --- a/gcc/config/loongarch/loongarch-def.c +++ b/gcc/config/loongarch/loongarch-def.c @@ -72,6 +72,18 @@ loongarch_cpu_cache[N_TUNE_TYPES] = { }, }; +struct loongarch_align +loongarch_cpu_align[N_TUNE_TYPES] = { + [CPU_LOONGARCH64] = { + .function = "32", + .label = "16", + }, + [CPU_LA464] = { + .function = "32", + .label = "16", + }, +}; + /* The following properties cannot be looked up directly using "cpucfg". So it is necessary to provide a default value for "unknown native" tune targets (i.e. -mtune=native while PRID does not correspond to diff --git a/gcc/config/loongarch/loongarch-def.h b/gcc/config/loongarch/loongarch-def.h index 778b1409956..fb8bb88eb52 100644 --- a/gcc/config/loongarch/loongarch-def.h +++ b/gcc/config/loongarch/loongarch-def.h @@ -144,6 +144,7 @@ extern int loongarch_cpu_issue_rate[]; extern int loongarch_cpu_multipass_dfa_lookahead[]; extern struct loongarch_cache loongarch_cpu_cache[]; +extern struct loongarch_align loongarch_cpu_align[]; extern struct loongarch_rtx_cost_data loongarch_cpu_rtx_cost_data[]; #ifdef __cplusplus diff --git a/gcc/config/loongarch/loongarch-tune.h b/gcc/config/loongarch/loongarch-tune.h index ba31c4f08c3..5c03262daff 100644 --- a/gcc/config/loongarch/loongarch-tune.h +++ b/gcc/config/loongarch/loongarch-tune.h @@ -48,4 +48,12 @@ struct loongarch_cache { int simultaneous_prefetches; /* number of parallel prefetch */ }; +/* Alignment for functions and labels for best performance. For new uarchs + the value should be measured via benchmarking. See the documentation for + -falign-functions and -falign-labels in invoke.texi for the format. */ +struct loongarch_align { + const char *function; /* default value for -falign-functions */ + const char *label; /* default value for -falign-labels */ +}; + #endif /* LOONGARCH_TUNE_H */ diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc index eb73d11b869..5b8b93eb24b 100644 --- a/gcc/config/loongarch/loongarch.cc +++ b/gcc/config/loongarch/loongarch.cc @@ -6249,6 +6249,12 @@ loongarch_option_override_internal (struct gcc_options *opts) && !opts->x_optimize_size) opts->x_flag_prefetch_loop_arrays = 1; + if (opts->x_flag_align_functions && !opts->x_str_align_functions) + opts->x_str_align_functions = loongarch_cpu_align[LARCH_ACTUAL_TUNE].function; + + if (opts->x_flag_align_labels && !opts->x_str_align_labels) + opts->x_str_align_labels = loongarch_cpu_align[LARCH_ACTUAL_TUNE].label; + if (TARGET_DIRECT_EXTERN_ACCESS && flag_shlib) error ("%qs cannot be used for compiling a shared library", "-mdirect-extern-access"); -- 2.41.0