radeonsi/gfx9: always wrap GS and TCS in an if-block (v2)
authorNicolai Hähnle <nicolai.haehnle@amd.com>
Fri, 14 Jul 2017 12:33:37 +0000 (14:33 +0200)
committerNicolai Hähnle <nicolai.haehnle@amd.com>
Thu, 27 Jul 2017 19:16:32 +0000 (21:16 +0200)
With merged ESGS shaders, the GS part of a wave may be empty, and the
hardware gets confused if any GS messages are sent from that wave. Since
S_SENDMSG is executed even when EXEC = 0, we have to wrap even
non-monolithic GS shaders in an if-block, so that the entire shader and
hence the S_SENDMSG instructions are skipped in empty waves.

This change is not required for TCS/HS, but applying it there as well
simplifies the logic a bit.

Fixes GL45-CTS.geometry_shader.rendering.rendering.*

v2: ensure that the TCS epilog doesn't run for non-existing patches

Cc: mesa-stable@lists.freedesktop.org
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
src/gallium/drivers/radeonsi/si_shader.c
src/gallium/drivers/radeonsi/si_shader_internal.h

index a153cb778435722e50050f19c1b0a26cf73c0890..9376d9066de0bf359ec0ec172eab2f9aecf0b66e 100644 (file)
@@ -174,6 +174,20 @@ unsigned si_shader_io_get_unique_index(unsigned semantic_name, unsigned index)
        }
 }
 
+/**
+ * Helper function that builds an LLVM IR PHI node and immediately adds
+ * incoming edges.
+ */
+static LLVMValueRef
+build_phi(struct ac_llvm_context *ctx, LLVMTypeRef type,
+         unsigned count_incoming, LLVMValueRef *values,
+         LLVMBasicBlockRef *blocks)
+{
+       LLVMValueRef phi = LLVMBuildPhi(ctx->builder, type, "");
+       LLVMAddIncoming(phi, values, blocks, count_incoming);
+       return phi;
+}
+
 /**
  * Get the value of a shader input parameter and extract a bitfield.
  */
@@ -2698,6 +2712,7 @@ si_insert_input_ptr_as_2xi32(struct si_shader_context *ctx, LLVMValueRef ret,
 static void si_llvm_emit_tcs_epilogue(struct lp_build_tgsi_context *bld_base)
 {
        struct si_shader_context *ctx = si_shader_context(bld_base);
+       LLVMBuilderRef builder = ctx->gallivm.builder;
        LLVMValueRef rel_patch_id, invocation_id, tf_lds_offset;
 
        si_copy_tcs_inputs(bld_base);
@@ -2706,8 +2721,29 @@ static void si_llvm_emit_tcs_epilogue(struct lp_build_tgsi_context *bld_base)
        invocation_id = unpack_param(ctx, ctx->param_tcs_rel_ids, 8, 5);
        tf_lds_offset = get_tcs_out_current_patch_data_offset(ctx);
 
+       if (ctx->screen->b.chip_class >= GFX9) {
+               LLVMBasicBlockRef blocks[2] = {
+                       LLVMGetInsertBlock(builder),
+                       ctx->merged_wrap_if_state.entry_block
+               };
+               LLVMValueRef values[2];
+
+               lp_build_endif(&ctx->merged_wrap_if_state);
+
+               values[0] = rel_patch_id;
+               values[1] = LLVMGetUndef(ctx->i32);
+               rel_patch_id = build_phi(&ctx->ac, ctx->i32, 2, values, blocks);
+
+               values[0] = tf_lds_offset;
+               values[1] = LLVMGetUndef(ctx->i32);
+               tf_lds_offset = build_phi(&ctx->ac, ctx->i32, 2, values, blocks);
+
+               values[0] = invocation_id;
+               values[1] = ctx->i32_1; /* cause the epilog to skip threads */
+               invocation_id = build_phi(&ctx->ac, ctx->i32, 2, values, blocks);
+       }
+
        /* Return epilog parameters from this function. */
-       LLVMBuilderRef builder = ctx->gallivm.builder;
        LLVMValueRef ret = ctx->return_value;
        unsigned vgpr;
 
@@ -2935,6 +2971,9 @@ static void si_llvm_emit_gs_epilogue(struct lp_build_tgsi_context *bld_base)
 
        ac_build_sendmsg(&ctx->ac, AC_SENDMSG_GS_OP_NOP | AC_SENDMSG_GS_DONE,
                         si_get_gs_wave_id(ctx));
+
+       if (ctx->screen->b.chip_class >= GFX9)
+               lp_build_endif(&ctx->merged_wrap_if_state);
 }
 
 static void si_llvm_emit_vs_epilogue(struct lp_build_tgsi_context *bld_base)
@@ -5502,14 +5541,20 @@ static bool si_compile_tgsi_main(struct si_shader_context *ctx,
        preload_ring_buffers(ctx);
 
        /* For GFX9 merged shaders:
-        * - Set EXEC. If the prolog is present, set EXEC there instead.
+        * - Set EXEC for the first shader. If the prolog is present, set
+        *   EXEC there instead.
         * - Add a barrier before the second shader.
+        * - In the second shader, reset EXEC to ~0 and wrap the main part in
+        *   an if-statement. This is required for correctness in geometry
+        *   shaders, to ensure that empty GS waves do not send GS_EMIT and
+        *   GS_CUT messages.
         *
-        * The same thing for monolithic shaders is done in
-        * si_build_wrapper_function.
+        * For monolithic merged shaders, the first shader is wrapped in an
+        * if-block together with its prolog in si_build_wrapper_function.
         */
-       if (ctx->screen->b.chip_class >= GFX9 && !is_monolithic) {
-               if (sel->info.num_instructions > 1 && /* not empty shader */
+       if (ctx->screen->b.chip_class >= GFX9) {
+               if (!is_monolithic &&
+                   sel->info.num_instructions > 1 && /* not empty shader */
                    (shader->key.as_es || shader->key.as_ls) &&
                    (ctx->type == PIPE_SHADER_TESS_EVAL ||
                     (ctx->type == PIPE_SHADER_VERTEX &&
@@ -5518,9 +5563,19 @@ static bool si_compile_tgsi_main(struct si_shader_context *ctx,
                                                ctx->param_merged_wave_info, 0);
                } else if (ctx->type == PIPE_SHADER_TESS_CTRL ||
                           ctx->type == PIPE_SHADER_GEOMETRY) {
-                       si_init_exec_from_input(ctx,
-                                               ctx->param_merged_wave_info, 8);
+                       if (!is_monolithic)
+                               si_init_exec_full_mask(ctx);
+
+                       /* The barrier must execute for all shaders in a
+                        * threadgroup.
+                        */
                        si_llvm_emit_barrier(NULL, bld_base, NULL);
+
+                       LLVMValueRef num_threads = unpack_param(ctx, ctx->param_merged_wave_info, 8, 8);
+                       LLVMValueRef ena =
+                               LLVMBuildICmp(ctx->ac.builder, LLVMIntULT,
+                                           ac_get_thread_id(&ctx->ac), num_threads, "");
+                       lp_build_if(&ctx->merged_wrap_if_state, &ctx->gallivm, ena);
                }
        }
 
@@ -5991,15 +6046,9 @@ static void si_build_wrapper_function(struct si_shader_context *ctx,
 
                /* Merged shaders are executed conditionally depending
                 * on the number of enabled threads passed in the input SGPRs. */
-               if (is_merged_shader(ctx->shader) &&
-                   (part == 0 || part == next_shader_first_part)) {
+               if (is_merged_shader(ctx->shader) && part == 0) {
                        LLVMValueRef ena, count = initial[3];
 
-                       /* The thread count for the 2nd shader is at bit-offset 8. */
-                       if (part == next_shader_first_part) {
-                               count = LLVMBuildLShr(builder, count,
-                                                     LLVMConstInt(ctx->i32, 8, 0), "");
-                       }
                        count = LLVMBuildAnd(builder, count,
                                             LLVMConstInt(ctx->i32, 0x7f, 0), "");
                        ena = LLVMBuildICmp(builder, LLVMIntULT,
@@ -6056,26 +6105,20 @@ static void si_build_wrapper_function(struct si_shader_context *ctx,
                ret = LLVMBuildCall(builder, parts[part], in, num_params, "");
 
                if (is_merged_shader(ctx->shader) &&
-                   (part + 1 == next_shader_first_part ||
-                    part + 1 == num_parts)) {
+                   part + 1 == next_shader_first_part) {
                        lp_build_endif(&if_state);
 
-                       if (part + 1 == next_shader_first_part) {
-                               /* A barrier is required between 2 merged shaders. */
-                               si_llvm_emit_barrier(NULL, &ctx->bld_base, NULL);
-
-                               /* The second half of the merged shader should use
-                                * the inputs from the toplevel (wrapper) function,
-                                * not the return value from the last call.
-                                *
-                                * That's because the last call was executed condi-
-                                * tionally, so we can't consume it in the main
-                                * block.
-                                */
-                               memcpy(out, initial, sizeof(initial));
-                               num_out = initial_num_out;
-                               num_out_sgpr = initial_num_out_sgpr;
-                       }
+                       /* The second half of the merged shader should use
+                        * the inputs from the toplevel (wrapper) function,
+                        * not the return value from the last call.
+                        *
+                        * That's because the last call was executed condi-
+                        * tionally, so we can't consume it in the main
+                        * block.
+                        */
+                       memcpy(out, initial, sizeof(initial));
+                       num_out = initial_num_out;
+                       num_out_sgpr = initial_num_out_sgpr;
                        continue;
                }
 
index 6e86e0b56dc83992c2708c519219e56b6647bea9..6b98bca27085b7cb086337448b09b20d8db1bc49 100644 (file)
@@ -25,6 +25,7 @@
 #define SI_SHADER_PRIVATE_H
 
 #include "si_shader.h"
+#include "gallivm/lp_bld_flow.h"
 #include "gallivm/lp_bld_init.h"
 #include "gallivm/lp_bld_tgsi.h"
 #include "tgsi/tgsi_parse.h"
@@ -105,6 +106,8 @@ struct si_shader_context {
        unsigned flow_depth;
        unsigned flow_depth_max;
 
+       struct lp_build_if_state merged_wrap_if_state;
+
        struct tgsi_array_info *temp_arrays;
        LLVMValueRef *temp_array_allocas;