nir: add a bool bitsize lowering pass

The pass lowers 1-bit booleans produced by NIR to the native bitsize
of the operations that produce them.

v2: change on lower_load_const_instr after upstream changes. Added
    TODO2 to explain it, as it was not properly tested yet (see
    already existing TODO) (Neil)

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3885>

4 files changed, 434 insertions, 0 deletions

diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
index 1b05b6bd955..170201e3d34 100644
--- a/src/compiler/Makefile.sources
+++ b/src/compiler/Makefile.sources
@@ -239,6 +239,7 @@ NIR_FILES = \
 	nir/nir_lower_atomics_to_ssbo.c \
 	nir/nir_lower_bitmap.c \
 	nir/nir_lower_bit_size.c \
+	nir/nir_lower_bool_to_bitsize.c \
 	nir/nir_lower_bool_to_float.c \
 	nir/nir_lower_bool_to_int32.c \
 	nir/nir_lower_clamp_color_outputs.c \
diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
index 37c64cab9fd..3e48eb1cf6a 100644
--- a/src/compiler/nir/meson.build
+++ b/src/compiler/nir/meson.build
@@ -118,6 +118,7 @@ files_libnir = files(
   'nir_lower_array_deref_of_vec.c',
   'nir_lower_atomics_to_ssbo.c',
   'nir_lower_bitmap.c',
+  'nir_lower_bool_to_bitsize.c',
   'nir_lower_bool_to_float.c',
   'nir_lower_bool_to_int32.c',
   'nir_lower_clamp_color_outputs.c',
diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
index 1fe0264cbe5..6a1a8e175df 100644
--- a/src/compiler/nir/nir.h
+++ b/src/compiler/nir/nir.h
@@ -3868,6 +3868,7 @@ bool nir_lower_flrp(nir_shader *shader, unsigned lowering_mask,
                     bool always_precise, bool have_ffma);
 
 bool nir_lower_alu_to_scalar(nir_shader *shader, nir_instr_filter_cb cb, const void *data);
+bool nir_lower_bool_to_bitsize(nir_shader *shader);
 bool nir_lower_bool_to_float(nir_shader *shader);
 bool nir_lower_bool_to_int32(nir_shader *shader);
 bool nir_lower_int_to_float(nir_shader *shader);
diff --git a/src/compiler/nir/nir_lower_bool_to_bitsize.c b/src/compiler/nir/nir_lower_bool_to_bitsize.c
new file mode 100644
index 00000000000..5561ffa14a4
--- /dev/null
+++ b/src/compiler/nir/nir_lower_bool_to_bitsize.c
@@ -0,0 +1,431 @@
+/*
+ * Copyright © 2018 Intel Corporation
+ *
+ * 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 "nir.h"
+#include "nir_builder.h"
+
+static bool
+assert_ssa_def_is_not_1bit(nir_ssa_def *def, UNUSED void *unused)
+{
+   assert(def->bit_size > 1);
+   return true;
+}
+
+static bool
+rewrite_1bit_ssa_def_to_32bit(nir_ssa_def *def, void *_progress)
+{
+   bool *progress = _progress;
+   if (def->bit_size == 1) {
+      def->bit_size = 32;
+      *progress = true;
+   }
+   return true;
+}
+
+static uint32_t
+get_bool_convert_opcode(uint32_t dst_bit_size)
+{
+   switch (dst_bit_size) {
+   case 32: return nir_op_i2i32;
+   case 16: return nir_op_i2i16;
+   case 8:  return nir_op_i2i8;
+   default:
+      unreachable("invalid boolean bit-size");
+   }
+}
+
+static void
+make_sources_canonical(nir_builder *b, nir_alu_instr *alu, uint32_t start_idx)
+{
+   /* TODO: for now we take the bit-size of the first source as the canonical
+    * form but we could try to be smarter.
+    */
+   const nir_op_info *op_info = &nir_op_infos[alu->op];
+   uint32_t bit_size = nir_src_bit_size(alu->src[start_idx].src);
+   for (uint32_t i = start_idx + 1; i < op_info->num_inputs; i++) {
+      if (nir_src_bit_size(alu->src[i].src) != bit_size) {
+         b->cursor = nir_before_instr(&alu->instr);
+         nir_op convert_op = get_bool_convert_opcode(bit_size);
+         nir_ssa_def *new_src =
+            nir_build_alu(b, convert_op, alu->src[i].src.ssa, NULL, NULL, NULL);
+         /* Retain the write mask and swizzle of the original instruction so
+          * that we don’t unnecessarily create a vectorized instruction.
+          */
+         nir_alu_instr *conv_instr =
+            nir_instr_as_alu(nir_builder_last_instr(b));
+         conv_instr->dest.write_mask = alu->dest.write_mask;
+         conv_instr->dest.dest.ssa.num_components =
+            alu->dest.dest.ssa.num_components;
+         memcpy(conv_instr->src[0].swizzle,
+                alu->src[i].swizzle,
+                sizeof(conv_instr->src[0].swizzle));
+         nir_instr_rewrite_src(&alu->instr,
+                               &alu->src[i].src, nir_src_for_ssa(new_src));
+         /* The swizzle will have been handled by the conversion instruction
+          * so we can reset it back to the default
+          */
+         for (unsigned j = 0; j < NIR_MAX_VEC_COMPONENTS; j++)
+            alu->src[i].swizzle[j] = j;
+      }
+   }
+}
+
+static bool
+lower_alu_instr(nir_builder *b, nir_alu_instr *alu)
+{
+   const nir_op_info *op_info = &nir_op_infos[alu->op];
+
+   /* For operations that can take multiple boolean sources we need to ensure
+    * that all booleans have the same bit-size
+    */
+   switch (alu->op) {
+   case nir_op_mov:
+   case nir_op_vec2:
+   case nir_op_vec3:
+   case nir_op_vec4:
+   case nir_op_inot:
+   case nir_op_iand:
+   case nir_op_ior:
+   case nir_op_ixor:
+      if (nir_dest_bit_size(alu->dest.dest) > 1)
+         break; /* Not a boolean instruction */
+      /* Fallthrough */
+
+   case nir_op_ball_fequal2:
+   case nir_op_ball_fequal3:
+   case nir_op_ball_fequal4:
+   case nir_op_bany_fnequal2:
+   case nir_op_bany_fnequal3:
+   case nir_op_bany_fnequal4:
+   case nir_op_ball_iequal2:
+   case nir_op_ball_iequal3:
+   case nir_op_ball_iequal4:
+   case nir_op_bany_inequal2:
+   case nir_op_bany_inequal3:
+   case nir_op_bany_inequal4:
+   case nir_op_ieq:
+   case nir_op_ine:
+      make_sources_canonical(b, alu, 0);
+      break;
+
+   case nir_op_bcsel:
+      /* bcsel may be choosing between boolean sources too */
+      if (nir_dest_bit_size(alu->dest.dest) == 1)
+         make_sources_canonical(b, alu, 1);
+      break;
+
+   default:
+      break;
+   }
+
+   /* Now that we have a canonical boolean bit-size, go on and rewrite the
+    * instruction to match the canonical bit-size.
+    */
+   uint32_t bit_size = nir_src_bit_size(alu->src[0].src);
+   assert(bit_size > 1);
+
+   nir_op opcode = alu->op;
+   switch (opcode) {
+   case nir_op_mov:
+   case nir_op_vec2:
+   case nir_op_vec3:
+   case nir_op_vec4:
+   case nir_op_inot:
+   case nir_op_iand:
+   case nir_op_ior:
+   case nir_op_ixor:
+      /* Nothing to do here, we do not specialize these opcodes by bit-size */
+      break;
+
+   case nir_op_f2b1:
+      opcode = bit_size == 8 ? nir_op_f2b8 :
+                               bit_size == 16 ? nir_op_f2b16 : nir_op_f2b32;
+      break;
+
+   case nir_op_i2b1:
+      opcode = bit_size == 8 ? nir_op_i2b8 :
+                               bit_size == 16 ? nir_op_i2b16 : nir_op_i2b32;
+      break;
+
+   case nir_op_flt:
+      opcode = bit_size == 8 ? nir_op_flt8 :
+                               bit_size == 16 ? nir_op_flt16 : nir_op_flt32;
+      break;
+
+   case nir_op_fge:
+      opcode = bit_size == 8 ? nir_op_fge8 :
+                               bit_size == 16 ? nir_op_fge16 : nir_op_fge32;
+      break;
+
+   case nir_op_feq:
+      opcode = bit_size == 8 ? nir_op_feq8 :
+                               bit_size == 16 ? nir_op_feq16 : nir_op_feq32;
+      break;
+
+   case nir_op_fne:
+      opcode = bit_size == 8 ? nir_op_fne8 :
+                               bit_size == 16 ? nir_op_fne16 : nir_op_fne32;
+      break;
+
+   case nir_op_ilt:
+      opcode = bit_size == 8 ? nir_op_ilt8 :
+                               bit_size == 16 ? nir_op_ilt16 : nir_op_ilt32;
+      break;
+
+   case nir_op_ige:
+      opcode = bit_size == 8 ? nir_op_ige8 :
+                               bit_size == 16 ? nir_op_ige16 : nir_op_ige32;
+      break;
+
+   case nir_op_ieq:
+      opcode = bit_size == 8 ? nir_op_ieq8 :
+                               bit_size == 16 ? nir_op_ieq16 : nir_op_ieq32;
+      break;
+
+   case nir_op_ine:
+      opcode = bit_size == 8 ? nir_op_ine8 :
+                               bit_size == 16 ? nir_op_ine16 : nir_op_ine32;
+      break;
+
+   case nir_op_ult:
+      opcode = bit_size == 8 ? nir_op_ult8 :
+                               bit_size == 16 ? nir_op_ult16 : nir_op_ult32;
+      break;
+
+   case nir_op_uge:
+      opcode = bit_size == 8 ? nir_op_uge8 :
+                               bit_size == 16 ? nir_op_uge16 : nir_op_uge32;
+      break;
+
+   case nir_op_ball_fequal2:
+      opcode = bit_size == 8 ? nir_op_b8all_fequal2 :
+                               bit_size == 16 ? nir_op_b16all_fequal2 :
+                                                nir_op_b32all_fequal2;
+      break;
+
+   case nir_op_ball_fequal3:
+      opcode = bit_size == 8 ? nir_op_b8all_fequal3 :
+                               bit_size == 16 ? nir_op_b16all_fequal3 :
+                                                nir_op_b32all_fequal3;
+      break;
+
+   case nir_op_ball_fequal4:
+      opcode = bit_size == 8 ? nir_op_b8all_fequal4 :
+                               bit_size == 16 ? nir_op_b16all_fequal4 :
+                                                nir_op_b32all_fequal4;
+      break;
+
+   case nir_op_bany_fnequal2:
+      opcode = bit_size == 8 ? nir_op_b8any_fnequal2 :
+                               bit_size == 16 ? nir_op_b16any_fnequal2 :
+                                                nir_op_b32any_fnequal2;
+      break;
+
+   case nir_op_bany_fnequal3:
+      opcode = bit_size == 8 ? nir_op_b8any_fnequal3 :
+                               bit_size == 16 ? nir_op_b16any_fnequal3 :
+                                                nir_op_b32any_fnequal3;
+      break;
+
+   case nir_op_bany_fnequal4:
+      opcode = bit_size == 8 ? nir_op_b8any_fnequal4 :
+                               bit_size == 16 ? nir_op_b16any_fnequal4 :
+                                                nir_op_b32any_fnequal4;
+      break;
+
+   case nir_op_ball_iequal2:
+      opcode = bit_size == 8 ? nir_op_b8all_iequal2 :
+                               bit_size == 16 ? nir_op_b16all_iequal2 :
+                                                nir_op_b32all_iequal2;
+      break;
+
+   case nir_op_ball_iequal3:
+      opcode = bit_size == 8 ? nir_op_b8all_iequal3 :
+                               bit_size == 16 ? nir_op_b16all_iequal3 :
+                                                nir_op_b32all_iequal3;
+      break;
+
+   case nir_op_ball_iequal4:
+      opcode = bit_size == 8 ? nir_op_b8all_iequal4 :
+                               bit_size == 16 ? nir_op_b16all_iequal4 :
+                                                nir_op_b32all_iequal4;
+      break;
+
+   case nir_op_bany_inequal2:
+      opcode = bit_size == 8 ? nir_op_b8any_inequal2 :
+                               bit_size == 16 ? nir_op_b16any_inequal2 :
+                                                nir_op_b32any_inequal2;
+      break;
+
+   case nir_op_bany_inequal3:
+      opcode = bit_size == 8 ? nir_op_b8any_inequal3 :
+                               bit_size == 16 ? nir_op_b16any_inequal3 :
+                                                nir_op_b32any_inequal3;
+      break;
+
+   case nir_op_bany_inequal4:
+      opcode = bit_size == 8 ? nir_op_b8any_inequal4 :
+                               bit_size == 16 ? nir_op_b16any_inequal4 :
+                                                nir_op_b32any_inequal4;
+      break;
+
+   case nir_op_bcsel:
+      opcode = bit_size == 8 ? nir_op_b8csel :
+                               bit_size == 16 ? nir_op_b16csel : nir_op_b32csel;
+
+      /* The destination of the selection may have a different bit-size from
+       * the bcsel condition.
+       */
+      bit_size = nir_src_bit_size(alu->src[1].src);
+      break;
+
+   default:
+      assert(alu->dest.dest.ssa.bit_size > 1);
+      for (unsigned i = 0; i < op_info->num_inputs; i++)
+         assert(alu->src[i].src.ssa->bit_size > 1);
+      return false;
+   }
+
+   alu->op = opcode;
+
+   if (alu->dest.dest.ssa.bit_size == 1)
+      alu->dest.dest.ssa.bit_size = bit_size;
+
+   return true;
+}
+
+static bool
+lower_load_const_instr(nir_load_const_instr *load)
+{
+   bool progress = false;
+
+   if (load->def.bit_size > 1)
+      return progress;
+
+   /* TODO: It is not clear if there is any case in which we can ever hit
+    * this path, so for now we just provide a 32-bit default.
+    *
+    * TODO2: after some changed on nir_const_value and other on upstream, we
+    * removed the initialization of a general value like this:
+    *   nir_const_value value = load->value
+    *
+    * to initialize per value component. Need to confirm if that is correct,
+    * but look at the TOO before.
+    */
+   for (unsigned i = 0; i < load->def.num_components; i++) {
+      load->value[i].u32 = load->value[i].b ? NIR_TRUE : NIR_FALSE;
+      load->def.bit_size = 32;
+      progress = true;
+   }
+
+   return progress;
+}
+
+static bool
+lower_phi_instr(nir_builder *b, nir_phi_instr *phi)
+{
+   if (nir_dest_bit_size(phi->dest) != 1)
+      return false;
+
+   /* Ensure all phi sources have a canonical bit-size. We choose the
+    * bit-size of the first phi source as the canonical form.
+    *
+    * TODO: maybe we can be smarter about how we choose the canonical form.
+    */
+   uint32_t dst_bit_size = 0;
+   nir_foreach_phi_src(phi_src, phi) {
+      uint32_t src_bit_size = nir_src_bit_size(phi_src->src);
+      if (dst_bit_size == 0) {
+         dst_bit_size = src_bit_size;
+      } else if (src_bit_size != dst_bit_size) {
+         assert(phi_src->src.is_ssa);
+         b->cursor = nir_before_src(&phi_src->src, false);
+         nir_op convert_op = get_bool_convert_opcode(dst_bit_size);
+         nir_ssa_def *new_src =
+            nir_build_alu(b, convert_op, phi_src->src.ssa, NULL, NULL, NULL);
+         nir_instr_rewrite_src(&phi->instr, &phi_src->src,
+                               nir_src_for_ssa(new_src));
+      }
+   }
+
+   phi->dest.ssa.bit_size = dst_bit_size;
+
+   return true;
+}
+
+static bool
+nir_lower_bool_to_bitsize_impl(nir_builder *b, nir_function_impl *impl)
+{
+   bool progress = false;
+
+   nir_foreach_block(block, impl) {
+      nir_foreach_instr_safe(instr, block) {
+         switch (instr->type) {
+         case nir_instr_type_alu:
+            progress |= lower_alu_instr(b, nir_instr_as_alu(instr));
+            break;
+
+         case nir_instr_type_load_const:
+            progress |= lower_load_const_instr(nir_instr_as_load_const(instr));
+            break;
+
+         case nir_instr_type_phi:
+            progress |= lower_phi_instr(b, nir_instr_as_phi(instr));
+            break;
+
+         case nir_instr_type_ssa_undef:
+         case nir_instr_type_intrinsic:
+         case nir_instr_type_tex:
+            nir_foreach_ssa_def(instr, rewrite_1bit_ssa_def_to_32bit,
+                                &progress);
+            break;
+
+         default:
+            nir_foreach_ssa_def(instr, assert_ssa_def_is_not_1bit, NULL);
+         }
+      }
+   }
+
+   if (progress) {
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+   }
+
+   return progress;
+}
+
+bool
+nir_lower_bool_to_bitsize(nir_shader *shader)
+{
+   nir_builder b;
+   bool progress = false;
+
+   nir_foreach_function(function, shader) {
+      if (function->impl) {
+         nir_builder_init(&b, function->impl);
+         progress = nir_lower_bool_to_bitsize_impl(&b, function->impl) || progress;
+      }
+   }
+
+   return progress;
+}