[Mesa-dev] [PATCH] radv/ac: setup mrt exports then export them in one go.

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

Noticed while looking at Sascha Willems deferred shaders.

This is a bit of an llvm workaround, llvm was producing this:
        v_cvt_pkrtz_f16_f32_e64 v4, v7, v8                       ; D2960004 00021107
        v_cvt_pkrtz_f16_f32_e64 v6, v9, 1.0                      ; D2960006 0001E509
        s_waitcnt vmcnt(0)                                       ; BF8C0F70
        exp mrt0 v4, v4, v6, v6 compr                            ; C400040F 00000604
        s_waitcnt expcnt(0)                                      ; BF8C0F0F
        v_cvt_pkrtz_f16_f32_e64 v4, v12, v5                      ; D2960004 00020B0C
        v_cvt_pkrtz_f16_f32_e64 v5, v14, 1.0                     ; D2960005 0001E50E
        exp mrt1 v4, v4, v5, v5 compr                            ; C400041F 00000504
        s_waitcnt expcnt(0)                                      ; BF8C0F0F
        v_cvt_pkrtz_f16_f32_e64 v0, v0, v1                       ; D2960000 00020300
        v_cvt_pkrtz_f16_f32_e64 v1, v2, v3                       ; D2960001 00020702
        exp mrt2 v0, v0, v1, v1 done compr vm                    ; C4001C2F 00000100

After this change:
        v_cvt_pkrtz_f16_f32_e64 v4, v7, v8                       ; D2960004 00021107
        s_waitcnt vmcnt(0)                                       ; BF8C0F70
        v_cvt_pkrtz_f16_f32_e64 v0, v0, v1                       ; D2960000 00020300
        v_cvt_pkrtz_f16_f32_e64 v6, v9, 1.0                      ; D2960006 0001E509
        v_cvt_pkrtz_f16_f32_e64 v5, v12, v5                      ; D2960005 00020B0C
        v_cvt_pkrtz_f16_f32_e64 v7, v14, 1.0                     ; D2960007 0001E50E
        exp mrt0 v4, v4, v6, v6 compr                            ; C400040F 00000604
        v_cvt_pkrtz_f16_f32_e64 v1, v2, v3                       ; D2960001 00020702
        exp mrt1 v5, v5, v7, v7 compr                            ; C400041F 00000705
        exp mrt2 v0, v0, v1, v1 done compr vm                    ; C4001C2F 00000100

No waitcnt for exports are emitted.

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 src/amd/common/ac_nir_to_llvm.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index 38d5359..4d2e469 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -5572,24 +5572,22 @@ handle_tcs_outputs_post(struct nir_to_llvm_context *ctx)
 	write_tess_factors(ctx);
 }
 
-static void
+static bool
 si_export_mrt_color(struct nir_to_llvm_context *ctx,
-		    LLVMValueRef *color, unsigned param, bool is_last)
+		    LLVMValueRef *color, unsigned param, bool is_last,
+		    struct ac_export_args *args)
 {
-
-	struct ac_export_args args;
-
 	/* Export */
 	si_llvm_init_export_args(ctx, color, param,
-				 &args);
+				 args);
 
 	if (is_last) {
-		args.valid_mask = 1; /* whether the EXEC mask is valid */
-		args.done = 1; /* DONE bit */
-	} else if (!args.enabled_channels)
-		return; /* unnecessary NULL export */
+		args->valid_mask = 1; /* whether the EXEC mask is valid */
+		args->done = 1; /* DONE bit */
+	} else if (!args->enabled_channels)
+		return false; /* unnecessary NULL export */
 
-	ac_build_export(&ctx->ac, &args);
+	return true;
 }
 
 static void
@@ -5639,6 +5637,7 @@ handle_fs_outputs_post(struct nir_to_llvm_context *ctx)
 {
 	unsigned index = 0;
 	LLVMValueRef depth = NULL, stencil = NULL, samplemask = NULL;
+	struct ac_export_args color_args[8];
 
 	for (unsigned i = 0; i < RADEON_LLVM_MAX_OUTPUTS; ++i) {
 		LLVMValueRef values[4];
@@ -5667,15 +5666,20 @@ handle_fs_outputs_post(struct nir_to_llvm_context *ctx)
 			if (!ctx->shader_info->fs.writes_z && !ctx->shader_info->fs.writes_stencil && !ctx->shader_info->fs.writes_sample_mask)
 				last = ctx->output_mask <= ((1ull << (i + 1)) - 1);
 
-			si_export_mrt_color(ctx, values, V_008DFC_SQ_EXP_MRT + index, last);
-			index++;
+			bool ret = si_export_mrt_color(ctx, values, V_008DFC_SQ_EXP_MRT + index, last, &color_args[index]);
+			if (ret)
+				index++;
 		}
 	}
 
+	for (unsigned i = 0; i < index; i++)
+		ac_build_export(&ctx->ac, &color_args[i]);
 	if (depth || stencil || samplemask)
 		si_export_mrt_z(ctx, depth, stencil, samplemask);
-	else if (!index)
-		si_export_mrt_color(ctx, NULL, V_008DFC_SQ_EXP_NULL, true);
+	else if (!index) {
+		si_export_mrt_color(ctx, NULL, V_008DFC_SQ_EXP_NULL, true, &color_args[0]);
+		ac_build_export(&ctx->ac, &color_args[0]);
+	}
 
 	ctx->shader_info->fs.output_mask = index ? ((1ull << index) - 1) : 0;
 }
-- 
2.7.4