intel/fs: Introduce regioning lowering pass.

This legalization pass is meant to handle situations where the source
or destination regioning controls of an instruction are unsupported by
the hardware and need to be lowered away into separate instructions.
This should be more reliable and future-proof than the current
approach of handling CHV/BXT restrictions manually all over the
visitor.  The same mechanism is leveraged to lower unsupported type
conversions easily, which obsoletes the lower_conversions pass.

v2: Give conditional modifiers the same treatment as predicates for
    SEL instructions in lower_dst_modifiers() (Iago).  Special-case a
    couple of other instructions with inconsistent conditional mod
    semantics in lower_dst_modifiers() (Curro).

Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

src/intel/Makefile.sources

@@ -64,6 +64,7 @@ COMPILER_FILES = \
 	compiler/brw_fs_live_variables.h \
 	compiler/brw_fs_lower_conversions.cpp \
 	compiler/brw_fs_lower_pack.cpp \
+	compiler/brw_fs_lower_regioning.cpp \
 	compiler/brw_fs_nir.cpp \
 	compiler/brw_fs_reg_allocate.cpp \
 	compiler/brw_fs_register_coalesce.cpp \

src/intel/compiler/brw_fs.cpp

@@ -6478,7 +6478,10 @@ fs_visitor::optimize()
       OPT(dead_code_eliminate);
    }
 
-   if (OPT(lower_conversions)) {
+   progress = false;
+   OPT(lower_conversions);
+   OPT(lower_regioning);
+   if (progress) {
       OPT(opt_copy_propagation);
       OPT(dead_code_eliminate);
       OPT(lower_simd_width);

src/intel/compiler/brw_fs.h

@@ -164,6 +164,7 @@ public:
    void lower_uniform_pull_constant_loads();
    bool lower_load_payload();
    bool lower_pack();
+   bool lower_regioning();
    bool lower_conversions();
    bool lower_logical_sends();
    bool lower_integer_multiplication();
@@ -536,24 +537,8 @@ namespace brw {
       }
    }
 
-   /**
-    * Remove any modifiers from the \p i-th source region of the instruction,
-    * including negate, abs and any implicit type conversion to the execution
-    * type.  Instead any source modifiers will be implemented as a separate
-    * MOV instruction prior to the original instruction.
-    */
-   inline bool
-   lower_src_modifiers(fs_visitor *v, bblock_t *block, fs_inst *inst, unsigned i)
-   {
-      assert(inst->components_read(i) == 1);
-      const fs_builder ibld(v, block, inst);
-      const fs_reg tmp = ibld.vgrf(get_exec_type(inst));
-
-      ibld.MOV(tmp, inst->src[i]);
-      inst->src[i] = tmp;
-
-      return true;
-   }
+   bool
+   lower_src_modifiers(fs_visitor *v, bblock_t *block, fs_inst *inst, unsigned i);
 }
 
 void shuffle_from_32bit_read(const brw::fs_builder &bld,

src/intel/compiler/brw_fs_lower_regioning.cpp

@@ -0,0 +1,399 @@
+/*
+ * 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 "brw_fs.h"
+#include "brw_cfg.h"
+#include "brw_fs_builder.h"
+
+using namespace brw;
+
+namespace {
+   /* From the SKL PRM Vol 2a, "Move":
+    *
+    * "A mov with the same source and destination type, no source modifier,
+    *  and no saturation is a raw move. A packed byte destination region (B
+    *  or UB type with HorzStride == 1 and ExecSize > 1) can only be written
+    *  using raw move."
+    */
+   bool
+   is_byte_raw_mov(const fs_inst *inst)
+   {
+      return type_sz(inst->dst.type) == 1 &&
+             inst->opcode == BRW_OPCODE_MOV &&
+             inst->src[0].type == inst->dst.type &&
+             !inst->saturate &&
+             !inst->src[0].negate &&
+             !inst->src[0].abs;
+   }
+
+   /*
+    * Return an acceptable byte stride for the destination of an instruction
+    * that requires it to have some particular alignment.
+    */
+   unsigned
+   required_dst_byte_stride(const fs_inst *inst)
+   {
+      if (type_sz(inst->dst.type) < get_exec_type_size(inst) &&
+          !is_byte_raw_mov(inst)) {
+         return get_exec_type_size(inst);
+      } else {
+         unsigned stride = inst->dst.stride * type_sz(inst->dst.type);
+
+         for (unsigned i = 0; i < inst->sources; i++) {
+            if (!is_uniform(inst->src[i]))
+               stride = MAX2(stride, inst->src[i].stride *
+                             type_sz(inst->src[i].type));
+         }
+
+         return stride;
+      }
+   }
+
+   /*
+    * Return an acceptable byte sub-register offset for the destination of an
+    * instruction that requires it to be aligned to the sub-register offset of
+    * the sources.
+    */
+   unsigned
+   required_dst_byte_offset(const fs_inst *inst)
+   {
+      for (unsigned i = 0; i < inst->sources; i++) {
+         if (!is_uniform(inst->src[i]))
+            if (reg_offset(inst->src[i]) % REG_SIZE !=
+                reg_offset(inst->dst) % REG_SIZE)
+               return 0;
+      }
+
+      return reg_offset(inst->dst) % REG_SIZE;
+   }
+
+   /*
+    * Return whether the instruction has an unsupported channel bit layout
+    * specified for the i-th source region.
+    */
+   bool
+   has_invalid_src_region(const gen_device_info *devinfo, const fs_inst *inst,
+                          unsigned i)
+   {
+      if (is_unordered(inst)) {
+         return false;
+      } else {
+         const unsigned dst_byte_stride = inst->dst.stride * type_sz(inst->dst.type);
+         const unsigned src_byte_stride = inst->src[i].stride *
+            type_sz(inst->src[i].type);
+         const unsigned dst_byte_offset = reg_offset(inst->dst) % REG_SIZE;
+         const unsigned src_byte_offset = reg_offset(inst->src[i]) % REG_SIZE;
+
+         return has_dst_aligned_region_restriction(devinfo, inst) &&
+                !is_uniform(inst->src[i]) &&
+                (src_byte_stride != dst_byte_stride ||
+                 src_byte_offset != dst_byte_offset);
+      }
+   }
+
+   /*
+    * Return whether the instruction has an unsupported channel bit layout
+    * specified for the destination region.
+    */
+   bool
+   has_invalid_dst_region(const gen_device_info *devinfo,
+                          const fs_inst *inst)
+   {
+      if (is_unordered(inst)) {
+         return false;
+      } else {
+         const brw_reg_type exec_type = get_exec_type(inst);
+         const unsigned dst_byte_offset = reg_offset(inst->dst) % REG_SIZE;
+         const unsigned dst_byte_stride = inst->dst.stride * type_sz(inst->dst.type);
+         const bool is_narrowing_conversion = !is_byte_raw_mov(inst) &&
+            type_sz(inst->dst.type) < type_sz(exec_type);
+
+         return (has_dst_aligned_region_restriction(devinfo, inst) &&
+                 (required_dst_byte_stride(inst) != dst_byte_stride ||
+                  required_dst_byte_offset(inst) != dst_byte_offset)) ||
+                (is_narrowing_conversion &&
+                 required_dst_byte_stride(inst) != dst_byte_stride);
+      }
+   }
+
+   /*
+    * Return whether the instruction has unsupported source modifiers
+    * specified for the i-th source region.
+    */
+   bool
+   has_invalid_src_modifiers(const gen_device_info *devinfo, const fs_inst *inst,
+                             unsigned i)
+   {
+      return !inst->can_do_source_mods(devinfo) &&
+             (inst->src[i].negate || inst->src[i].abs);
+   }
+
+   /*
+    * Return whether the instruction has an unsupported type conversion
+    * specified for the destination.
+    */
+   bool
+   has_invalid_conversion(const gen_device_info *devinfo, const fs_inst *inst)
+   {
+      switch (inst->opcode) {
+      case BRW_OPCODE_MOV:
+         return false;
+      case BRW_OPCODE_SEL:
+         return inst->dst.type != get_exec_type(inst);
+      case SHADER_OPCODE_BROADCAST:
+      case SHADER_OPCODE_MOV_INDIRECT:
+         /* The source and destination types of these may be hard-coded to
+          * integer at codegen time due to hardware limitations of 64-bit
+          * types.
+          */
+         return ((devinfo->gen == 7 && !devinfo->is_haswell) ||
+                 devinfo->is_cherryview || gen_device_info_is_9lp(devinfo)) &&
+                type_sz(inst->src[0].type) > 4 &&
+                inst->dst.type != inst->src[0].type;
+      default:
+         /* FIXME: We assume the opcodes don't explicitly mentioned before
+          * just work fine with arbitrary conversions.
+          */
+         return false;
+      }
+   }
+
+   /**
+    * Return whether the instruction has non-standard semantics for the
+    * conditional mod which don't cause the flag register to be updated with
+    * the comparison result.
+    */
+   bool
+   has_inconsistent_cmod(const fs_inst *inst)
+   {
+      return inst->opcode == BRW_OPCODE_SEL ||
+             inst->opcode == BRW_OPCODE_CSEL ||
+             inst->opcode == BRW_OPCODE_IF ||
+             inst->opcode == BRW_OPCODE_WHILE;
+   }
+
+   bool
+   lower_instruction(fs_visitor *v, bblock_t *block, fs_inst *inst);
+}
+
+namespace brw {
+   /**
+    * Remove any modifiers from the \p i-th source region of the instruction,
+    * including negate, abs and any implicit type conversion to the execution
+    * type.  Instead any source modifiers will be implemented as a separate
+    * MOV instruction prior to the original instruction.
+    */
+   bool
+   lower_src_modifiers(fs_visitor *v, bblock_t *block, fs_inst *inst, unsigned i)
+   {
+      assert(inst->components_read(i) == 1);
+      const fs_builder ibld(v, block, inst);
+      const fs_reg tmp = ibld.vgrf(get_exec_type(inst));
+
+      lower_instruction(v, block, ibld.MOV(tmp, inst->src[i]));
+      inst->src[i] = tmp;
+
+      return true;
+   }
+}
+
+namespace {
+   /**
+    * Remove any modifiers from the destination region of the instruction,
+    * including saturate, conditional mod and any implicit type conversion
+    * from the execution type.  Instead any destination modifiers will be
+    * implemented as a separate MOV instruction after the original
+    * instruction.
+    */
+   bool
+   lower_dst_modifiers(fs_visitor *v, bblock_t *block, fs_inst *inst)
+   {
+      const fs_builder ibld(v, block, inst);
+      const brw_reg_type type = get_exec_type(inst);
+      /* Not strictly necessary, but if possible use a temporary with the same
+       * channel alignment as the current destination in order to avoid
+       * violating the restrictions enforced later on by lower_src_region()
+       * and lower_dst_region(), which would introduce additional copy
+       * instructions into the program unnecessarily.
+       */
+      const unsigned stride =
+         type_sz(inst->dst.type) * inst->dst.stride <= type_sz(type) ? 1 :
+         type_sz(inst->dst.type) * inst->dst.stride / type_sz(type);
+      const fs_reg tmp = horiz_stride(ibld.vgrf(type, stride), stride);
+
+      /* Emit a MOV taking care of all the destination modifiers. */
+      fs_inst *mov = ibld.at(block, inst->next).MOV(inst->dst, tmp);
+      mov->saturate = inst->saturate;
+      if (!has_inconsistent_cmod(inst))
+         mov->conditional_mod = inst->conditional_mod;
+      if (inst->opcode != BRW_OPCODE_SEL) {
+         mov->predicate = inst->predicate;
+         mov->predicate_inverse = inst->predicate_inverse;
+      }
+      mov->flag_subreg = inst->flag_subreg;
+      lower_instruction(v, block, mov);
+
+      /* Point the original instruction at the temporary, and clean up any
+       * destination modifiers.
+       */
+      assert(inst->size_written == inst->dst.component_size(inst->exec_size));
+      inst->dst = tmp;
+      inst->size_written = inst->dst.component_size(inst->exec_size);
+      inst->saturate = false;
+      if (!has_inconsistent_cmod(inst))
+         inst->conditional_mod = BRW_CONDITIONAL_NONE;
+
+      assert(!inst->flags_written() || !mov->predicate);
+      return true;
+   }
+
+   /**
+    * Remove any non-trivial shuffling of data from the \p i-th source region
+    * of the instruction.  Instead implement the region as a series of integer
+    * copies into a temporary with the same channel layout as the destination.
+    */
+   bool
+   lower_src_region(fs_visitor *v, bblock_t *block, fs_inst *inst, unsigned i)
+   {
+      assert(inst->components_read(i) == 1);
+      const fs_builder ibld(v, block, inst);
+      const unsigned stride = type_sz(inst->dst.type) * inst->dst.stride /
+                              type_sz(inst->src[i].type);
+      assert(stride > 0);
+      const fs_reg tmp = horiz_stride(ibld.vgrf(inst->src[i].type, stride),
+                                      stride);
+
+      /* Emit a series of 32-bit integer copies with any source modifiers
+       * cleaned up (because their semantics are dependent on the type).
+       */
+      const brw_reg_type raw_type = brw_int_type(MIN2(type_sz(tmp.type), 4),
+                                                 false);
+      const unsigned n = type_sz(tmp.type) / type_sz(raw_type);
+      fs_reg raw_src = inst->src[i];
+      raw_src.negate = false;
+      raw_src.abs = false;
+
+      for (unsigned j = 0; j < n; j++)
+         ibld.MOV(subscript(tmp, raw_type, j), subscript(raw_src, raw_type, j));
+
+      /* Point the original instruction at the temporary, making sure to keep
+       * any source modifiers in the instruction.
+       */
+      fs_reg lower_src = tmp;
+      lower_src.negate = inst->src[i].negate;
+      lower_src.abs = inst->src[i].abs;
+      inst->src[i] = lower_src;
+
+      return true;
+   }
+
+   /**
+    * Remove any non-trivial shuffling of data from the destination region of
+    * the instruction.  Instead implement the region as a series of integer
+    * copies from a temporary with a channel layout compatible with the
+    * sources.
+    */
+   bool
+   lower_dst_region(fs_visitor *v, bblock_t *block, fs_inst *inst)
+   {
+      const fs_builder ibld(v, block, inst);
+      const unsigned stride = required_dst_byte_stride(inst) /
+                              type_sz(inst->dst.type);
+      assert(stride > 0);
+      const fs_reg tmp = horiz_stride(ibld.vgrf(inst->dst.type, stride),
+                                      stride);
+
+      /* Emit a series of 32-bit integer copies from the temporary into the
+       * original destination.
+       */
+      const brw_reg_type raw_type = brw_int_type(MIN2(type_sz(tmp.type), 4),
+                                                 false);
+      const unsigned n = type_sz(tmp.type) / type_sz(raw_type);
+
+      if (inst->predicate && inst->opcode != BRW_OPCODE_SEL) {
+         /* Note that in general we cannot simply predicate the copies on the
+          * same flag register as the original instruction, since it may have
+          * been overwritten by the instruction itself.  Instead initialize
+          * the temporary with the previous contents of the destination
+          * register.
+          */
+         for (unsigned j = 0; j < n; j++)
+            ibld.MOV(subscript(tmp, raw_type, j),
+                     subscript(inst->dst, raw_type, j));
+      }
+
+      for (unsigned j = 0; j < n; j++)
+         ibld.at(block, inst->next).MOV(subscript(inst->dst, raw_type, j),
+                                        subscript(tmp, raw_type, j));
+
+      /* Point the original instruction at the temporary, making sure to keep
+       * any destination modifiers in the instruction.
+       */
+      assert(inst->size_written == inst->dst.component_size(inst->exec_size));
+      inst->dst = tmp;
+      inst->size_written = inst->dst.component_size(inst->exec_size);
+
+      return true;
+   }
+
+   /**
+    * Legalize the source and destination regioning controls of the specified
+    * instruction.
+    */
+   bool
+   lower_instruction(fs_visitor *v, bblock_t *block, fs_inst *inst)
+   {
+      const gen_device_info *devinfo = v->devinfo;
+      bool progress = false;
+
+      if (has_invalid_conversion(devinfo, inst))
+         progress |= lower_dst_modifiers(v, block, inst);
+
+      if (has_invalid_dst_region(devinfo, inst))
+         progress |= lower_dst_region(v, block, inst);
+
+      for (unsigned i = 0; i < inst->sources; i++) {
+         if (has_invalid_src_modifiers(devinfo, inst, i))
+            progress |= lower_src_modifiers(v, block, inst, i);
+
+         if (has_invalid_src_region(devinfo, inst, i))
+            progress |= lower_src_region(v, block, inst, i);
+      }
+
+      return progress;
+   }
+}
+
+bool
+fs_visitor::lower_regioning()
+{
+   bool progress = false;
+
+   foreach_block_and_inst_safe(block, fs_inst, inst, cfg)
+      progress |= lower_instruction(this, block, inst);
+
+   if (progress)
+      invalidate_live_intervals();
+
+   return progress;
+}

src/intel/compiler/brw_ir_fs.h

@@ -486,6 +486,16 @@ get_exec_type_size(const fs_inst *inst)
    return type_sz(get_exec_type(inst));
 }
 
+/**
+ * Return whether the instruction isn't an ALU instruction and cannot be
+ * assumed to complete in-order.
+ */
+static inline bool
+is_unordered(const fs_inst *inst)
+{
+   return inst->mlen || inst->is_send_from_grf() || inst->is_math();
+}
+
 /**
  * Return whether the following regioning restriction applies to the specified
  * instruction.  From the Cherryview PRM Vol 7. "Register Region

src/intel/compiler/meson.build

@@ -57,6 +57,7 @@ libintel_compiler_files = files(
   'brw_fs_live_variables.h',
   'brw_fs_lower_conversions.cpp',
   'brw_fs_lower_pack.cpp',
+  'brw_fs_lower_regioning.cpp',
   'brw_fs_nir.cpp',
   'brw_fs_reg_allocate.cpp',
   'brw_fs_register_coalesce.cpp',