[Mesa-stable] [BACKPORT staging/19.0] ac/nir: mark some texture intrinsics as convergent

[Rhys Perry]

Otherwise LLVM can sink them and their texture coordinate calculations
into divergent branches.

v2: simplify the conditions on which the intrinsic is marked as convergent
v3: only mark as convergent in FS and CS with derivative groups

Signed-off-by: Rhys Perry <pendingchaos02 at gmail.com>
Reviewed-by: Marek Olšák <marek.olsak at amd.com>
---
 src/amd/common/ac_nir_to_llvm.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/src/amd/common/ac_nir_to_llvm.c b/src/amd/common/ac_nir_to_llvm.c
index a0815995b12..774ac299753 100644
--- a/src/amd/common/ac_nir_to_llvm.c
+++ b/src/amd/common/ac_nir_to_llvm.c
@@ -1381,6 +1381,20 @@ static LLVMValueRef build_tex_intrinsic(struct ac_nir_context *ctx,
 	}
 
 	args->attributes = AC_FUNC_ATTR_READNONE;
+	if (ctx->stage == MESA_SHADER_FRAGMENT) {
+		/* Prevent texture instructions with implicit derivatives from being
+		 * sinked into branches. */
+		switch (instr->op) {
+		case nir_texop_tex:
+		case nir_texop_txb:
+		case nir_texop_lod:
+			args->attributes |= AC_FUNC_ATTR_CONVERGENT;
+			break;
+		default:
+			break;
+		}
+	}
+
 	return ac_build_image_opcode(&ctx->ac, args);
 }
 
-- 
2.21.0