radeonsi: don't emit unnecessary NULL exports for unbound targets (v3)

v2: remove semantic index == 0 checks
    add the else statement to remove shadowing of args
v3: fix fbo-alphatest-nocolor regression

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com> (v2)

diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
index db922f01fb8bd16fd14b2712b321f6f3e508009c..34b84eb81d9d02eef8ade73abc3ef871ce4d3561 100644 (file)
--- a/src/gallium/drivers/radeonsi/si_shader.c
+++ b/src/gallium/drivers/radeonsi/si_shader.c
@@ -2287,7 +2287,6 @@ static void si_export_mrt_color(struct lp_build_tgsi_context *bld_base,
 {
        struct si_shader_context *si_shader_ctx = si_shader_context(bld_base);
        struct lp_build_context *base = &bld_base->base;
-       LLVMValueRef args[9];
        int i;
 
        /* Clamp color */
@@ -2309,27 +2308,46 @@ static void si_export_mrt_color(struct lp_build_tgsi_context *bld_base,
                color[3] = si_scale_alpha_by_sample_mask(bld_base, color[3]);
 
        /* If last_cbuf > 0, FS_COLOR0_WRITES_ALL_CBUFS is true. */
-       if (index == 0 &&
-           si_shader_ctx->shader->key.ps.last_cbuf > 0) {
-               for (int c = 1; c <= si_shader_ctx->shader->key.ps.last_cbuf; c++) {
+       if (si_shader_ctx->shader->key.ps.last_cbuf > 0) {
+               LLVMValueRef args[8][9];
+               int c, last = -1;
+
+               /* Get the export arguments, also find out what the last one is. */
+               for (c = 0; c <= si_shader_ctx->shader->key.ps.last_cbuf; c++) {
                        si_llvm_init_export_args(bld_base, color,
-                                                V_008DFC_SQ_EXP_MRT + c, args);
+                                                V_008DFC_SQ_EXP_MRT + c, args[c]);
+                       if (args[c][0] != bld_base->uint_bld.zero)
+                               last = c;
+               }
+
+               /* Emit all exports. */
+               for (c = 0; c <= si_shader_ctx->shader->key.ps.last_cbuf; c++) {
+                       if (is_last && last == c) {
+                               args[c][1] = bld_base->uint_bld.one; /* whether the EXEC mask is valid */
+                               args[c][2] = bld_base->uint_bld.one; /* DONE bit */
+                       } else if (args[c][0] == bld_base->uint_bld.zero)
+                               continue; /* unnecessary NULL export */
+
                        lp_build_intrinsic(base->gallivm->builder, "llvm.SI.export",
                                           LLVMVoidTypeInContext(base->gallivm->context),
-                                          args, 9, 0);
+                                          args[c], 9, 0);
                }
+       } else {
+               LLVMValueRef args[9];
+
+               /* Export */
+               si_llvm_init_export_args(bld_base, color, V_008DFC_SQ_EXP_MRT + index,
+                                        args);
+               if (is_last) {
+                       args[1] = bld_base->uint_bld.one; /* whether the EXEC mask is valid */
+                       args[2] = bld_base->uint_bld.one; /* DONE bit */
+               } else if (args[0] == bld_base->uint_bld.zero)
+                       return; /* unnecessary NULL export */
+
+               lp_build_intrinsic(base->gallivm->builder, "llvm.SI.export",
+                                  LLVMVoidTypeInContext(base->gallivm->context),
+                                  args, 9, 0);
        }
-
-       /* Export */
-       si_llvm_init_export_args(bld_base, color, V_008DFC_SQ_EXP_MRT + index,
-                                args);
-       if (is_last) {
-               args[1] = bld_base->uint_bld.one; /* whether the EXEC mask is valid */
-               args[2] = bld_base->uint_bld.one; /* DONE bit */
-       }
-       lp_build_intrinsic(base->gallivm->builder, "llvm.SI.export",
-                          LLVMVoidTypeInContext(base->gallivm->context),
-                          args, 9, 0);
 }
 
 static void si_export_null(struct lp_build_tgsi_context *bld_base)
@@ -2364,19 +2382,43 @@ static void si_llvm_emit_fs_epilogue(struct lp_build_tgsi_context * bld_base)
        int last_color_export = -1;
        int i;
 
-       /* If there are no outputs, add a dummy export. */
-       if (!info->num_outputs) {
-               si_export_null(bld_base);
-               return;
-       }
-
        /* Determine the last export. If MRTZ is present, it's always last.
         * Otherwise, find the last color export.
         */
-       if (!info->writes_z && !info->writes_stencil && !info->writes_samplemask)
-               for (i = 0; i < info->num_outputs; i++)
-                       if (info->output_semantic_name[i] == TGSI_SEMANTIC_COLOR)
+       if (!info->writes_z && !info->writes_stencil && !info->writes_samplemask) {
+               unsigned spi_format = shader->key.ps.spi_shader_col_format;
+
+               /* Don't export NULL and return if alpha-test is enabled. */
+               if (shader->key.ps.alpha_func != PIPE_FUNC_ALWAYS &&
+                   shader->key.ps.alpha_func != PIPE_FUNC_NEVER &&
+                   (spi_format & 0xf) == 0)
+                       spi_format |= V_028714_SPI_SHADER_32_AR;
+
+               for (i = 0; i < info->num_outputs; i++) {
+                       unsigned index = info->output_semantic_index[i];
+
+                       if (info->output_semantic_name[i] != TGSI_SEMANTIC_COLOR)
+                               continue;
+
+                       /* If last_cbuf > 0, FS_COLOR0_WRITES_ALL_CBUFS is true. */
+                       if (shader->key.ps.last_cbuf > 0) {
+                               /* Just set this if any of the colorbuffers are enabled. */
+                               if (spi_format &
+                                   ((1llu << (4 * (shader->key.ps.last_cbuf + 1))) - 1))
+                                       last_color_export = i;
+                               continue;
+                       }
+
+                       if ((spi_format >> (index * 4)) & 0xf)
                                last_color_export = i;
+               }
+
+               /* If there are no outputs, export NULL. */
+               if (last_color_export == -1) {
+                       si_export_null(bld_base);
+                       return;
+               }
+       }
 
        for (i = 0; i < info->num_outputs; i++) {
                unsigned semantic_name = info->output_semantic_name[i];