[Mesa-dev] [PATCH] ac/nir: don't trash L1 caches for store operations with writeonly memory

[Samuel Pitoiset]

Ported from RadeonSI.

Signed-off-by: Samuel Pitoiset <samuel.pitoi...@gmail.com>
---
 src/amd/common/ac_nir_to_llvm.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index 81a4149c321..bcec66fa107 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -1465,7 +1465,8 @@ static LLVMValueRef extract_vector_range(struct 
ac_llvm_context *ctx, LLVMValueR
 
 static unsigned get_cache_policy(struct ac_nir_context *ctx,
                                 enum gl_access_qualifier access,
-                                bool may_store_unaligned)
+                                bool may_store_unaligned,
+                                bool writeonly_memory)
 {
        unsigned cache_policy = 0;
 
@@ -1474,6 +1475,11 @@ static unsigned get_cache_policy(struct ac_nir_context 
*ctx,
         * get unaligned stores is through shader images.
         */
        if (((may_store_unaligned && ctx->ac.chip_class == SI) ||
+            /* If this is write-only, don't keep data in L1 to prevent
+             * evicting L1 cache lines that may be needed by other
+             * instructions.
+             */
+            writeonly_memory ||
             access & (ACCESS_COHERENT | ACCESS_VOLATILE))) {
                cache_policy |= ac_glc;
        }
@@ -1489,7 +1495,8 @@ static void visit_store_ssbo(struct ac_nir_context *ctx,
        int elem_size_bytes = ac_get_elem_bits(&ctx->ac, LLVMTypeOf(src_data)) 
/ 8;
        unsigned writemask = nir_intrinsic_write_mask(instr);
        enum gl_access_qualifier access = nir_intrinsic_access(instr);
-       unsigned cache_policy = get_cache_policy(ctx, access, false);
+       bool writeonly_memory = access & ACCESS_NON_READABLE;
+       unsigned cache_policy = get_cache_policy(ctx, access, false, 
writeonly_memory);
        LLVMValueRef glc = (cache_policy & ac_glc) ? ctx->ac.i1true : 
ctx->ac.i1false;
 
        LLVMValueRef rsrc = ctx->abi->load_ssbo(ctx->abi,
@@ -1646,7 +1653,7 @@ static LLVMValueRef visit_load_buffer(struct 
ac_nir_context *ctx,
        int elem_size_bytes = instr->dest.ssa.bit_size / 8;
        int num_components = instr->num_components;
        enum gl_access_qualifier access = nir_intrinsic_access(instr);
-       unsigned cache_policy = get_cache_policy(ctx, access, false);
+       unsigned cache_policy = get_cache_policy(ctx, access, false, false);
        LLVMValueRef glc = (cache_policy & ac_glc) ? ctx->ac.i1true : 
ctx->ac.i1false;
 
        LLVMValueRef offset = get_src(ctx, instr->src[1]);
@@ -2359,7 +2366,8 @@ static LLVMValueRef visit_image_load(struct 
ac_nir_context *ctx,
 
        type = glsl_without_array(type);
 
-       args.cache_policy = get_cache_policy(ctx, var->data.image.access, 
false);
+       args.cache_policy =
+               get_cache_policy(ctx, var->data.image.access, false, false);
 
        const enum glsl_sampler_dim dim = glsl_get_sampler_dim(type);
        if (dim == GLSL_SAMPLER_DIM_BUF) {
@@ -2401,9 +2409,11 @@ static void visit_image_store(struct ac_nir_context *ctx,
        const nir_variable *var = get_image_variable(instr);
        const struct glsl_type *type = glsl_without_array(var->type);
        const enum glsl_sampler_dim dim = glsl_get_sampler_dim(type);
+       bool writeonly_memory = var->data.image.access & ACCESS_NON_READABLE;
        struct ac_image_args args = {};
 
-       args.cache_policy = get_cache_policy(ctx, var->data.image.access, true);
+       args.cache_policy = get_cache_policy(ctx, var->data.image.access, true,
+                                            writeonly_memory);
 
        if (dim == GLSL_SAMPLER_DIM_BUF) {
                char name[48];
-- 
2.20.1

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