ac/llvm: remove the low-optimizing compiler option

Not needed with ACO. It was used for big shaders on old APUs that took
forever to compile.

Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33046>

src/amd/llvm/ac_llvm_util.c

@@ -171,13 +171,6 @@ bool ac_init_llvm_compiler(struct ac_llvm_compiler *compiler, enum radeon_family
    if (!compiler->tm)
       return false;
 
-   if (tm_options & AC_TM_CREATE_LOW_OPT) {
-      compiler->low_opt_tm =
-         ac_create_target_machine(family, tm_options, LLVMCodeGenLevelLess, NULL);
-      if (!compiler->low_opt_tm)
-         goto fail;
-   }
-
    compiler->meo =
       ac_create_midend_optimizer(compiler->tm, tm_options & AC_TM_CHECK_IR);
    if (!compiler->meo)
@@ -193,14 +186,11 @@ void ac_destroy_llvm_compiler(struct ac_llvm_compiler *compiler)
 {
    /* delete the codegen pass managers */
    ac_destroy_backend_optimizer(compiler->beo);
-   ac_destroy_backend_optimizer(compiler->low_opt_beo);
 
    /* delete optimizer pass manager */
    if (compiler->meo)
       ac_destroy_midend_optimiser(compiler->meo);
 
-   if (compiler->low_opt_tm)
-      LLVMDisposeTargetMachine(compiler->low_opt_tm);
    if (compiler->tm)
       LLVMDisposeTargetMachine(compiler->tm);
 }

src/amd/llvm/ac_llvm_util.h

@@ -31,7 +31,6 @@ enum ac_target_machine_options
 {
    AC_TM_SUPPORTS_SPILL       = 1 << 0,
    AC_TM_CHECK_IR             = 1 << 1,
-   AC_TM_CREATE_LOW_OPT       = 1 << 2,
 };
 
 enum ac_float_mode
@@ -47,12 +46,6 @@ struct ac_llvm_compiler {
    LLVMTargetMachineRef tm;
    struct ac_midend_optimizer *meo;
    struct ac_backend_optimizer *beo;
-
-   /* Optional compiler for faster compilation with fewer optimizations.
-    * LLVM modules can be created with "tm" too. There is no difference.
-    */
-   LLVMTargetMachineRef low_opt_tm; /* uses -O1 instead of -O2 */
-   struct ac_backend_optimizer *low_opt_beo;
 };
 
 LLVMTargetRef ac_get_llvm_target(const char *triple);

src/gallium/drivers/radeonsi/si_pipe.c

@@ -143,22 +143,11 @@ struct ac_llvm_compiler *si_create_llvm_compiler(struct si_screen *sscreen)
    if (!compiler)
       return NULL;
 
-   /* Only create the less-optimizing version of the compiler on APUs
-    * predating Ryzen (Raven). */
-   bool create_low_opt_compiler =
-      !sscreen->info.has_dedicated_vram && sscreen->info.gfx_level <= GFX8;
-
-   enum ac_target_machine_options tm_options =
-      (sscreen->debug_flags & DBG(CHECK_IR) ? AC_TM_CHECK_IR : 0) |
-      (create_low_opt_compiler ? AC_TM_CREATE_LOW_OPT : 0);
-
-   if (!ac_init_llvm_compiler(compiler, sscreen->info.family, tm_options))
+   if (!ac_init_llvm_compiler(compiler, sscreen->info.family,
+                              sscreen->debug_flags & DBG(CHECK_IR) ? AC_TM_CHECK_IR : 0))
       return NULL;
 
    compiler->beo = ac_create_backend_optimizer(compiler->tm);
-   if (compiler->low_opt_tm)
-      compiler->low_opt_beo = ac_create_backend_optimizer(compiler->low_opt_tm);
-
    return compiler;
 #else
    return NULL;

src/gallium/drivers/radeonsi/si_shader_llvm.c

@@ -54,7 +54,7 @@ static void si_diagnostic_handler(LLVMDiagnosticInfoRef di, void *context)
 bool si_compile_llvm(struct si_screen *sscreen, struct si_shader_binary *binary,
                      struct ac_shader_config *conf, struct ac_llvm_compiler *compiler,
                      struct ac_llvm_context *ac, struct util_debug_callback *debug,
-                     gl_shader_stage stage, const char *name, bool less_optimized)
+                     gl_shader_stage stage, const char *name)
 {
    unsigned count = p_atomic_inc_return(&sscreen->num_compilations);
 
@@ -75,9 +75,6 @@ bool si_compile_llvm(struct si_screen *sscreen, struct si_shader_binary *binary,
    if (!si_replace_shader(count, binary)) {
       struct ac_backend_optimizer *beo = compiler->beo;
 
-      if (less_optimized && compiler->low_opt_beo)
-         beo = compiler->low_opt_beo;
-
       struct si_llvm_diagnostics diag = {debug};
       LLVMContextSetDiagnosticHandler(ac->context, si_diagnostic_handler, &diag);
 
@@ -781,20 +778,6 @@ static bool si_llvm_translate_nir(struct si_shader_context *ctx, struct si_shade
    return true;
 }
 
-static bool si_should_optimize_less(struct ac_llvm_compiler *compiler,
-                                    struct si_shader_selector *sel)
-{
-   if (!compiler->low_opt_beo)
-      return false;
-
-   /* Assume a slow CPU. */
-   assert(!sel->screen->info.has_dedicated_vram && sel->screen->info.gfx_level <= GFX8);
-
-   /* For a crazy dEQP test containing 2597 memory opcodes, mostly
-    * buffer stores. */
-   return sel->stage == MESA_SHADER_COMPUTE && sel->info.num_memory_stores > 1000;
-}
-
 bool si_llvm_compile_shader(struct si_screen *sscreen, struct ac_llvm_compiler *compiler,
                             struct si_shader *shader, struct si_shader_args *args,
                             struct util_debug_callback *debug, struct nir_shader *nir)
@@ -858,8 +841,7 @@ bool si_llvm_compile_shader(struct si_screen *sscreen, struct ac_llvm_compiler *
 
    /* Compile to bytecode. */
    if (!si_compile_llvm(sscreen, &shader->binary, &shader->config, compiler, &ctx.ac, debug,
-                        nir->info.stage, si_get_shader_name(shader),
-                        si_should_optimize_less(compiler, shader->selector))) {
+                        nir->info.stage, si_get_shader_name(shader))) {
       si_llvm_dispose(&ctx);
       fprintf(stderr, "LLVM failed to compile shader\n");
       return false;
@@ -932,7 +914,7 @@ bool si_llvm_build_shader_part(struct si_screen *sscreen, gl_shader_stage stage,
    si_llvm_optimize_module(&ctx);
 
    bool ret = si_compile_llvm(sscreen, &result->binary, &result->config, compiler,
-                              &ctx.ac, debug, ctx.stage, name, false);
+                              &ctx.ac, debug, ctx.stage, name);
 
    si_llvm_dispose(&ctx);
    return ret;

src/gallium/drivers/radeonsi/si_shader_llvm.h

@@ -51,7 +51,7 @@ static inline struct si_shader_context *si_shader_context_from_abi(struct ac_sha
 bool si_compile_llvm(struct si_screen *sscreen, struct si_shader_binary *binary,
                      struct ac_shader_config *conf, struct ac_llvm_compiler *compiler,
                      struct ac_llvm_context *ac, struct util_debug_callback *debug,
-                     gl_shader_stage stage, const char *name, bool less_optimized);
+                     gl_shader_stage stage, const char *name);
 void si_llvm_context_init(struct si_shader_context *ctx, struct si_screen *sscreen,
                           struct ac_llvm_compiler *compiler, unsigned wave_size,
                           bool exports_color_null, bool exports_mrtz,