pan/{mdg, bi}: Lower load_helper_invocation

Passes dEQP-GLES31.functional.shaders.helper_invocation.* on both
architectures

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8774>

src/panfrost/Makefile.sources

@@ -102,6 +102,7 @@ util_FILES := \
         util/pan_ir.h \
         util/pan_liveness.c \
         util/pan_lower_framebuffer.c \
+        util/pan_lower_helper_invocation.c \
         util/pan_lower_writeout.c \
         util/pan_lower_64bit_intrin.c \
         util/pan_sysval.c \

src/panfrost/bifrost/bifrost_compile.c

@@ -2356,6 +2356,7 @@ bi_optimize_nir(nir_shader *nir)
         };
 
         NIR_PASS(progress, nir, pan_nir_lower_64bit_intrin);
+        NIR_PASS(progress, nir, pan_lower_helper_invocation);
 
         NIR_PASS(progress, nir, nir_lower_int64);
 

src/panfrost/midgard/midgard_compile.c

@@ -318,6 +318,7 @@ optimise_nir(nir_shader *nir, unsigned quirks, bool is_blend)
         /* Midgard image ops coordinates are 16-bit instead of 32-bit */
         NIR_PASS(progress, nir, midgard_nir_lower_image_bitsize);
         NIR_PASS(progress, nir, midgard_nir_lower_helper_writes);
+        NIR_PASS(progress, nir, pan_lower_helper_invocation);
 
         NIR_PASS(progress, nir, midgard_nir_lower_algebraic_early);
 

src/panfrost/util/meson.build

@@ -27,6 +27,7 @@ libpanfrost_util_files = files(
   'pan_ir.h',
   'pan_liveness.c',
   'pan_lower_framebuffer.c',
+  'pan_lower_helper_invocation.c',
   'pan_lower_writeout.c',
   'pan_lower_64bit_intrin.c',
   'pan_sysval.c',

src/panfrost/util/pan_ir.h

@@ -283,4 +283,6 @@ bool pan_nir_lower_zs_store(nir_shader *nir);
 
 bool pan_nir_lower_64bit_intrin(nir_shader *shader);
 
+bool pan_lower_helper_invocation(nir_shader *shader);
+
 #endif

src/panfrost/util/pan_lower_helper_invocation.c

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2021 Collabora, Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "pan_ir.h"
+#include "compiler/nir/nir_builder.h"
+
+/* Lower gl_HelperInvocation to (gl_SampleMaskIn == 0), this depends on
+ * architectural details but is required for correct operation with
+ * multisampling. NIR's lowering won't work for us, since there is no in-spec
+ * way to implement load_sample_id_no_per_sample. */
+
+static bool
+pan_lower_helper_invocation_instr(nir_builder *b, nir_instr *instr, void *data)
+{
+        if (instr->type != nir_instr_type_intrinsic)
+                return false;
+
+        nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
+        if (intr->intrinsic != nir_intrinsic_load_helper_invocation)
+                return false;
+
+        b->cursor = nir_before_instr(instr);
+
+        nir_ssa_def *mask = nir_load_sample_mask_in(b);
+        nir_ssa_def *eq = nir_ieq(b, mask, nir_imm_int(b, 0));
+        nir_ssa_def_rewrite_uses(&intr->dest.ssa, nir_src_for_ssa(eq));
+
+        return true;
+}
+
+bool
+pan_lower_helper_invocation(nir_shader *shader)
+{
+        return nir_shader_instructions_pass(shader,
+                                            pan_lower_helper_invocation_instr,
+                                            nir_metadata_block_index | nir_metadata_dominance,
+                                            NULL);
+}