Mesa (main): r600: Add a helper function for rat_index_mode, with documentation and assert.

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Module: Mesa
Branch: main
Commit: 8dcf7646ceed42c2b28094667aa24b236baf79c1
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=8dcf7646ceed42c2b28094667aa24b236baf79c1

Author: Emma Anholt <emma at anholt.net>
Date:   Thu Apr  7 15:15:03 2022 -0700

r600: Add a helper function for rat_index_mode, with documentation and assert.

We have some special requirements on the address regs of our incoming
TGSI, which nir_to_tgsi violated.

Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15824>

---

 src/gallium/drivers/r600/r600_shader.c | 32 +++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/src/gallium/drivers/r600/r600_shader.c b/src/gallium/drivers/r600/r600_shader.c
index 7b0b83a80fb..ddd2acaca9f 100644
--- a/src/gallium/drivers/r600/r600_shader.c
+++ b/src/gallium/drivers/r600/r600_shader.c
@@ -8851,6 +8851,20 @@ static int load_buffer_coord(struct r600_shader_ctx *ctx, int src_idx,
 	return 0;
 }
 
+/* ADDR[1,2] are stored in index_reg[0,1] on EG, and can be used for indexing
+ * images and ssbos.  We assume that indirects are indexed by ADDR[2], as that's
+ * what GLSL-to-TGSI emitted.
+ */
+static unsigned tgsi_indirect_to_rat_index_mode(struct tgsi_ind_register ind)
+{
+	if (ind.File == TGSI_FILE_NULL)
+		return 0; /* CF_INDEX_NONE */
+	else {
+		assert(ind.Index == 2);
+		return 2; /* CF_INDEX_1 */
+	}
+}
+
 static int tgsi_load_buffer(struct r600_shader_ctx *ctx)
 {
 	struct tgsi_full_instruction *inst = &ctx->parse.FullToken.FullInstruction;
@@ -8859,10 +8873,9 @@ static int tgsi_load_buffer(struct r600_shader_ctx *ctx)
 	struct r600_bytecode_cf *cf;
 	int r;
 	int temp_reg = r600_get_temp(ctx);
-	unsigned rat_index_mode;
+	unsigned rat_index_mode = tgsi_indirect_to_rat_index_mode(inst->Src[0].Indirect);
 	unsigned base;
 
-	rat_index_mode = inst->Src[0].Indirect.Index == 2 ? 2 : 0; // CF_INDEX_1 : CF_INDEX_NONE
 	base = R600_IMAGE_REAL_RESOURCE_OFFSET + ctx->info.file_count[TGSI_FILE_IMAGE];
 
 	r = load_buffer_coord(ctx, 1, temp_reg);
@@ -8917,11 +8930,9 @@ static int tgsi_load_rat(struct r600_shader_ctx *ctx)
 	int idx_gpr;
 	unsigned format, num_format, format_comp, endian;
 	const struct util_format_description *desc;
-	unsigned rat_index_mode;
+	unsigned rat_index_mode = tgsi_indirect_to_rat_index_mode(inst->Src[0].Indirect);
 	unsigned immed_base;
 
-	rat_index_mode = inst->Src[0].Indirect.Index == 2 ? 2 : 0; // CF_INDEX_1 : CF_INDEX_NONE
-
 	immed_base = R600_IMAGE_IMMED_RESOURCE_OFFSET;
 	r = load_index_src(ctx, 1, &idx_gpr);
 	if (r)
@@ -9022,7 +9033,7 @@ static int tgsi_store_buffer_rat(struct r600_shader_ctx *ctx)
 	struct tgsi_full_instruction *inst = &ctx->parse.FullToken.FullInstruction;
 	struct r600_bytecode_cf *cf;
 	int r, i;
-	unsigned rat_index_mode;
+	unsigned rat_index_mode = tgsi_indirect_to_rat_index_mode(inst->Dst[0].Indirect);
 	int lasti;
 	int temp_reg = r600_get_temp(ctx), treg2 = r600_get_temp(ctx);
 
@@ -9030,7 +9041,6 @@ static int tgsi_store_buffer_rat(struct r600_shader_ctx *ctx)
 	if (r)
 		return r;
 
-	rat_index_mode = inst->Dst[0].Indirect.Index == 2 ? 2 : 0; // CF_INDEX_1 : CF_INDEX_NONE
 	if (rat_index_mode)
 		egcm_load_index_reg(ctx->bc, 1, false);
 
@@ -9107,9 +9117,7 @@ static int tgsi_store_rat(struct r600_shader_ctx *ctx)
 	bool src_requires_loading = false;
 	int val_gpr, idx_gpr;
 	int r, i;
-	unsigned rat_index_mode;
-
-	rat_index_mode = inst->Dst[0].Indirect.Index == 2 ? 2 : 0; // CF_INDEX_1 : CF_INDEX_NONE
+	unsigned rat_index_mode = tgsi_indirect_to_rat_index_mode(inst->Dst[0].Indirect);
 
 	r = load_index_src(ctx, 0, &idx_gpr);
 	if (r)
@@ -9252,7 +9260,7 @@ static int tgsi_atomic_op_rat(struct r600_shader_ctx *ctx)
 	int idx_gpr;
 	unsigned format, num_format, format_comp, endian;
 	const struct util_format_description *desc;
-	unsigned rat_index_mode;
+	unsigned rat_index_mode = tgsi_indirect_to_rat_index_mode(inst->Src[0].Indirect);
 	unsigned immed_base;
 	unsigned rat_base;
 
@@ -9273,8 +9281,6 @@ static int tgsi_atomic_op_rat(struct r600_shader_ctx *ctx)
 			return r;
 	}
 
-	rat_index_mode = inst->Src[0].Indirect.Index == 2 ? 2 : 0; // CF_INDEX_1 : CF_INDEX_NONE
-
 	if (ctx->inst_info->op == V_RAT_INST_CMPXCHG_INT_RTN) {
 		memset(&alu, 0, sizeof(struct r600_bytecode_alu));
 		alu.op = ALU_OP1_MOV;