ac/llvm: fix nir_texop_texture_samples with NULL descriptors

With VK_EXT_robustness2, descriptors can be NULL and the number of
samples returned by nir_texop_texture_samples should be 0.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4775>

diff --git a/src/amd/llvm/ac_nir_to_llvm.c b/src/amd/llvm/ac_nir_to_llvm.c
index 28c4a4c404e6c09cbdef37bea8a7f6b9be8a40bc..2a495eb76e4e21a8d95ebcc676812bdc95961493 100644 (file)
--- a/src/amd/llvm/ac_nir_to_llvm.c
+++ b/src/amd/llvm/ac_nir_to_llvm.c
@@ -4469,6 +4469,8 @@ static void visit_tex(struct ac_nir_context *ctx, nir_tex_instr *instr)
 
        if (instr->op == nir_texop_texture_samples) {
                LLVMValueRef res, samples, is_msaa;
+               LLVMValueRef default_sample;
+
                res = LLVMBuildBitCast(ctx->ac.builder, args.resource, ctx->ac.v8i32, "");
                samples = LLVMBuildExtractElement(ctx->ac.builder, res,
                                                  LLVMConstInt(ctx->ac.i32, 3, false), "");
@@ -4485,8 +4487,27 @@ static void visit_tex(struct ac_nir_context *ctx, nir_tex_instr *instr)
                                       LLVMConstInt(ctx->ac.i32, 0xf, false), "");
                samples = LLVMBuildShl(ctx->ac.builder, ctx->ac.i32_1,
                                       samples, "");
+
+               if (ctx->abi->robust_buffer_access) {
+                       LLVMValueRef dword1, is_null_descriptor;
+
+                       /* Extract the second dword of the descriptor, if it's
+                        * all zero, then it's a null descriptor.
+                        */
+                       dword1 = LLVMBuildExtractElement(ctx->ac.builder, res,
+                                                        LLVMConstInt(ctx->ac.i32, 1, false), "");
+                       is_null_descriptor =
+                               LLVMBuildICmp(ctx->ac.builder, LLVMIntEQ, dword1,
+                                             LLVMConstInt(ctx->ac.i32, 0, false), "");
+                       default_sample =
+                               LLVMBuildSelect(ctx->ac.builder, is_null_descriptor,
+                                               ctx->ac.i32_0, ctx->ac.i32_1, "");
+               } else {
+                       default_sample = ctx->ac.i32_1;
+               }
+
                samples = LLVMBuildSelect(ctx->ac.builder, is_msaa, samples,
-                                         ctx->ac.i32_1, "");
+                                         default_sample, "");
                result = samples;
                goto write_result;
        }