[Mesa-dev] [PATCH 3/5] ac: LDS stores in LS and ES don't have to be volatile

Marek Olšák maraeo at gmail.com
Thu Nov 9 22:41:20 UTC 2017


From: Marek Olšák <marek.olsak at amd.com>

I like the writeonly wrapper more than using ac_build_store directly.
---
 src/amd/common/ac_llvm_build.c           |  6 ++++++
 src/amd/common/ac_llvm_build.h           |  2 ++
 src/amd/common/ac_nir_to_llvm.c          |  4 ++--
 src/gallium/drivers/radeonsi/si_shader.c | 15 ++++++++++-----
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/src/amd/common/ac_llvm_build.c b/src/amd/common/ac_llvm_build.c
index a85ffe1..4c9beda 100644
--- a/src/amd/common/ac_llvm_build.c
+++ b/src/amd/common/ac_llvm_build.c
@@ -1771,20 +1771,26 @@ LLVMValueRef ac_lds_load_volatile(struct ac_llvm_context *ctx,
 {
 	return ac_build_load_custom(ctx, ctx->lds, dw_addr, false, false, true);
 }
 
 void ac_lds_store_volatile(struct ac_llvm_context *ctx,
 			   LLVMValueRef dw_addr, LLVMValueRef value)
 {
 	ac_build_store(ctx, ctx->lds, dw_addr, ac_to_integer(ctx, value), true);
 }
 
+void ac_lds_store_writeonly(struct ac_llvm_context *ctx,
+			    LLVMValueRef dw_addr, LLVMValueRef value)
+{
+	ac_build_store(ctx, ctx->lds, dw_addr, ac_to_integer(ctx, value), false);
+}
+
 LLVMValueRef ac_find_lsb(struct ac_llvm_context *ctx,
 			 LLVMTypeRef dst_type,
 			 LLVMValueRef src0)
 {
 	LLVMValueRef params[2] = {
 		src0,
 
 		/* The value of 1 means that ffs(x=0) = undef, so LLVM won't
 		 * add special code to check for x=0. The reason is that
 		 * the LLVM behavior for x=0 is different from what we
diff --git a/src/amd/common/ac_llvm_build.h b/src/amd/common/ac_llvm_build.h
index e3f716e..25a540a 100644
--- a/src/amd/common/ac_llvm_build.h
+++ b/src/amd/common/ac_llvm_build.h
@@ -288,19 +288,21 @@ void ac_optimize_vs_outputs(struct ac_llvm_context *ac,
 			    uint8_t *vs_output_param_offset,
 			    uint32_t num_outputs,
 			    uint8_t *num_param_exports);
 void ac_init_exec_full_mask(struct ac_llvm_context *ctx);
 
 void ac_declare_lds_as_pointer(struct ac_llvm_context *ac);
 LLVMValueRef ac_lds_load_volatile(struct ac_llvm_context *ctx,
 				  LLVMValueRef dw_addr);
 void ac_lds_store_volatile(struct ac_llvm_context *ctx,
 			   LLVMValueRef dw_addr, LLVMValueRef value);
+void ac_lds_store_writeonly(struct ac_llvm_context *ctx,
+			    LLVMValueRef dw_addr, LLVMValueRef value);
 
 LLVMValueRef ac_find_lsb(struct ac_llvm_context *ctx,
 			 LLVMTypeRef dst_type,
 			 LLVMValueRef src0);
 #ifdef __cplusplus
 }
 #endif
 
 #endif
diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index fa30b91..3f41b9f 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -5841,21 +5841,21 @@ handle_es_outputs_post(struct nir_to_llvm_context *ctx,
 		if (lds_base) {
 			dw_addr = LLVMBuildAdd(ctx->builder, lds_base,
 			                       LLVMConstInt(ctx->ac.i32, param_index * 4, false),
 			                       "");
 		}
 		for (j = 0; j < length; j++) {
 			LLVMValueRef out_val = LLVMBuildLoad(ctx->builder, out_ptr[j], "");
 			out_val = LLVMBuildBitCast(ctx->builder, out_val, ctx->ac.i32, "");
 
 			if (ctx->ac.chip_class  >= GFX9) {
-				ac_lds_store_volatile(&ctx->ac, dw_addr,
+				ac_lds_store_writeonly(&ctx->ac, dw_addr,
 					     LLVMBuildLoad(ctx->builder, out_ptr[j], ""));
 				dw_addr = LLVMBuildAdd(ctx->builder, dw_addr, ctx->ac.i32_1, "");
 			} else {
 				ac_build_buffer_store_dword(&ctx->ac,
 				                            ctx->esgs_ring,
 				                            out_val, 1,
 				                            NULL, ctx->es2gs_offset,
 				                            (4 * param_index + j) * 4,
 				                            1, 1, true, true);
 			}
@@ -5881,21 +5881,21 @@ handle_ls_outputs_post(struct nir_to_llvm_context *ctx)
 		if (i == VARYING_SLOT_CLIP_DIST0)
 			length = ctx->num_output_clips + ctx->num_output_culls;
 		int param = shader_io_get_unique_index(i);
 		mark_tess_output(ctx, false, param);
 		if (length > 4)
 			mark_tess_output(ctx, false, param + 1);
 		LLVMValueRef dw_addr = LLVMBuildAdd(ctx->builder, base_dw_addr,
 						    LLVMConstInt(ctx->ac.i32, param * 4, false),
 						    "");
 		for (unsigned j = 0; j < length; j++) {
-			ac_lds_store_volatile(&ctx->ac, dw_addr,
+			ac_lds_store_writeonly(&ctx->ac, dw_addr,
 				     LLVMBuildLoad(ctx->builder, out_ptr[j], ""));
 			dw_addr = LLVMBuildAdd(ctx->builder, dw_addr, ctx->ac.i32_1, "");
 		}
 	}
 }
 
 struct ac_build_if_state
 {
 	struct nir_to_llvm_context *ctx;
 	LLVMValueRef condition;
diff --git a/src/gallium/drivers/radeonsi/si_shader.c b/src/gallium/drivers/radeonsi/si_shader.c
index ec4cf89..98ac914 100644
--- a/src/gallium/drivers/radeonsi/si_shader.c
+++ b/src/gallium/drivers/radeonsi/si_shader.c
@@ -1110,28 +1110,31 @@ static LLVMValueRef lds_load(struct lp_build_tgsi_context *bld_base,
 
 /**
  * Store to LDS.
  *
  * \param swizzle	offset (typically 0..3)
  * \param dw_addr	address in dwords
  * \param value		value to store
  */
 static void lds_store(struct lp_build_tgsi_context *bld_base,
 		      unsigned dw_offset_imm, LLVMValueRef dw_addr,
-		      LLVMValueRef value)
+		      LLVMValueRef value, bool Volatile)
 {
 	struct si_shader_context *ctx = si_shader_context(bld_base);
 
 	dw_addr = lp_build_add(&bld_base->uint_bld, dw_addr,
 			    LLVMConstInt(ctx->i32, dw_offset_imm, 0));
 
-	ac_lds_store_volatile(&ctx->ac, dw_addr, value);
+	if (Volatile)
+		ac_lds_store_volatile(&ctx->ac, dw_addr, value);
+	else
+		ac_lds_store_writeonly(&ctx->ac, dw_addr, value);
 }
 
 static LLVMValueRef desc_from_addr_base64k(struct si_shader_context *ctx,
 						  unsigned param)
 {
 	LLVMBuilderRef builder = ctx->ac.builder;
 
 	LLVMValueRef addr = LLVMGetParam(ctx->main_fn, param);
 	addr = LLVMBuildZExt(builder, addr, ctx->i64, "");
 	addr = LLVMBuildShl(builder, addr, LLVMConstInt(ctx->i64, 16, 0), "");
@@ -1260,21 +1263,21 @@ static void store_output_tcs(struct lp_build_tgsi_context *bld_base,
 	uint32_t writemask = reg->Register.WriteMask;
 	while (writemask) {
 		chan_index = u_bit_scan(&writemask);
 		LLVMValueRef value = dst[chan_index];
 
 		if (inst->Instruction.Saturate)
 			value = ac_build_clamp(&ctx->ac, value);
 
 		/* Skip LDS stores if there is no LDS read of this output. */
 		if (!skip_lds_store)
-			lds_store(bld_base, chan_index, dw_addr, value);
+			lds_store(bld_base, chan_index, dw_addr, value, true);
 
 		value = ac_to_integer(&ctx->ac, value);
 		values[chan_index] = value;
 
 		if (reg->Register.WriteMask != 0xF && !is_tess_factor) {
 			ac_build_buffer_store_dword(&ctx->ac, buffer, value, 1,
 						    buf_addr, base,
 						    4 * chan_index, 1, 0, true, false);
 		}
 
@@ -3179,21 +3182,22 @@ static void si_llvm_emit_ls_epilogue(struct lp_build_tgsi_context *bld_base)
 		if (name == TGSI_SEMANTIC_LAYER ||
 		    name == TGSI_SEMANTIC_VIEWPORT_INDEX)
 			continue;
 
 		int param = si_shader_io_get_unique_index(name, index);
 		LLVMValueRef dw_addr = LLVMBuildAdd(ctx->ac.builder, base_dw_addr,
 					LLVMConstInt(ctx->i32, param * 4, 0), "");
 
 		for (chan = 0; chan < 4; chan++) {
 			lds_store(bld_base, chan, dw_addr,
-				  LLVMBuildLoad(ctx->ac.builder, out_ptr[chan], ""));
+				  LLVMBuildLoad(ctx->ac.builder, out_ptr[chan], ""),
+				  false);
 		}
 	}
 
 	if (ctx->screen->b.chip_class >= GFX9)
 		si_set_ls_return_value_for_tcs(ctx);
 }
 
 static void si_llvm_emit_es_epilogue(struct lp_build_tgsi_context *bld_base)
 {
 	struct si_shader_context *ctx = si_shader_context(bld_base);
@@ -3226,21 +3230,22 @@ static void si_llvm_emit_es_epilogue(struct lp_build_tgsi_context *bld_base)
 
 		param = si_shader_io_get_unique_index(info->output_semantic_name[i],
 						      info->output_semantic_index[i]);
 
 		for (chan = 0; chan < 4; chan++) {
 			LLVMValueRef out_val = LLVMBuildLoad(ctx->ac.builder, out_ptr[chan], "");
 			out_val = ac_to_integer(&ctx->ac, out_val);
 
 			/* GFX9 has the ESGS ring in LDS. */
 			if (ctx->screen->b.chip_class >= GFX9) {
-				lds_store(bld_base, param * 4 + chan, lds_base, out_val);
+				lds_store(bld_base, param * 4 + chan, lds_base, out_val,
+					  false);
 				continue;
 			}
 
 			ac_build_buffer_store_dword(&ctx->ac,
 						    ctx->esgs_ring,
 						    out_val, 1, NULL, soffset,
 						    (4 * param + chan) * 4,
 						    1, 1, true, true);
 		}
 	}
-- 
2.7.4



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