Mesa (master): ac/llvm: fix nir_texop_texture_samples with NULL descriptors

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Module: Mesa
Branch: master
Commit: aa94213781447525e2e5da90ee9c72ad0a57527f
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=aa94213781447525e2e5da90ee9c72ad0a57527f

Author: Samuel Pitoiset <samuel.pitoiset at gmail.com>
Date:   Mon Apr 27 13:04:40 2020 +0200

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 at gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas at basnieuwenhuizen.nl>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4775>

---

 src/amd/llvm/ac_nir_to_llvm.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/amd/llvm/ac_nir_to_llvm.c b/src/amd/llvm/ac_nir_to_llvm.c
index 28c4a4c404e..2a495eb76e4 100644
--- 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;
 	}