nir: add nir_lower_amul pass

Lower amul to either imul or imul24, depending on whether 24b is enough
bits to calculate an offset within the thing being dereferenced.

Signed-off-by: Rob Clark <[email protected]>

1 files changed, 316 insertions, 0 deletions

diff --git a/src/compiler/nir/nir_lower_amul.c b/src/compiler/nir/nir_lower_amul.c
new file mode 100644
index 00000000000..4c7f10859cb
--- /dev/null
+++ b/src/compiler/nir/nir_lower_amul.c
@@ -0,0 +1,316 @@
+/*
+ * Copyright © 2019 Google, Inc.
+ *
+ * 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_vla.h"
+
+/* Lowering for amul instructions, for drivers that support imul24.
+ * This pass will analyze indirect derefs, and convert corresponding
+ * amul instructions to either imul or imul24, depending on the
+ * required range.
+ *
+ * 1) Analyze the uniform variables and build a table of UBOs and SSBOs
+ *    that are either too large, or might be too large (unknown size)
+ *    for imul24
+ *
+ * 2) Loop thru looking at all the intrinsics, finding dereferences of
+ *    large variables, and recursively replacing all amul instructions
+ *    used with imul
+ *
+ * 3) Finally loop again thru all instructions replacing any remaining
+ *    amul with imul24.  At this point any remaining amul instructions
+ *    are not involved in calculating an offset into a large variable,
+ *    thanks to the 2nd step, so they can be safely replace with imul24.
+ *
+ * Using two passes over all the instructions lets us handle the case
+ * where, due to CSE, an amul is used to calculate an offset into both
+ * a large and small variable.
+ */
+
+typedef struct {
+   int (*type_size)(const struct glsl_type *, bool);
+
+   /* Tables of UBOs and SSBOs mapping driver_location/base whether
+    * they are too large to use imul24:
+    */
+   bool *large_ubos;
+   bool *large_ssbos;
+
+   /* for cases that we cannot determine UBO/SSBO index, track if *any*
+    * UBO/SSBO is too large for imul24:
+    */
+   bool has_large_ubo;
+   bool has_large_ssbo;
+} lower_state;
+
+/* Lower 'amul's in offset src of large variables to 'imul': */
+static bool
+lower_large_src(nir_src *src, void *s)
+{
+   lower_state *state = s;
+
+   assert(src->is_ssa);
+
+   nir_instr *parent = src->ssa->parent_instr;
+
+   /* No need to visit instructions we've already visited.. this also
+    * avoids infinite recursion when phi's are involved:
+    */
+   if (parent->pass_flags)
+      return false;
+
+   bool progress = nir_foreach_src(parent, lower_large_src, state);
+
+   if (parent->type == nir_instr_type_alu) {
+      nir_alu_instr *alu = nir_instr_as_alu(parent);
+      if (alu->op == nir_op_amul) {
+         alu->op = nir_op_imul;
+         progress = true;
+      }
+   }
+
+   parent->pass_flags = 1;
+
+   return progress;
+}
+
+static bool
+large_ubo(lower_state *state, nir_src src)
+{
+   if (!nir_src_is_const(src))
+      return state->has_large_ubo;
+   return state->large_ubos[nir_src_as_uint(src)];
+}
+
+static bool
+large_ssbo(lower_state *state, nir_src src)
+{
+   if (!nir_src_is_const(src))
+      return state->has_large_ssbo;
+   return state->large_ssbos[nir_src_as_uint(src)];
+}
+
+static bool
+lower_intrinsic(lower_state *state, nir_intrinsic_instr *intr)
+{
+   switch (intr->intrinsic) {
+   case nir_intrinsic_load_ubo:
+      //# src[] = { buffer_index, offset }.
+      if (large_ubo(state, intr->src[0]))
+         return lower_large_src(&intr->src[1], state);
+      return false;
+
+   case nir_intrinsic_load_ssbo:
+      //# src[] = { buffer_index, offset }.
+      if (large_ssbo(state, intr->src[0]))
+         return lower_large_src(&intr->src[1], state);
+      return false;
+
+   case nir_intrinsic_store_ssbo:
+      //# src[] = { value, block_index, offset }
+      if (large_ssbo(state, intr->src[1]))
+         return lower_large_src(&intr->src[2], state);
+      return false;
+
+   case nir_intrinsic_ssbo_atomic_add:
+   case nir_intrinsic_ssbo_atomic_imin:
+   case nir_intrinsic_ssbo_atomic_umin:
+   case nir_intrinsic_ssbo_atomic_imax:
+   case nir_intrinsic_ssbo_atomic_umax:
+   case nir_intrinsic_ssbo_atomic_and:
+   case nir_intrinsic_ssbo_atomic_or:
+   case nir_intrinsic_ssbo_atomic_xor:
+   case nir_intrinsic_ssbo_atomic_exchange:
+   case nir_intrinsic_ssbo_atomic_comp_swap:
+   case nir_intrinsic_ssbo_atomic_fadd:
+   case nir_intrinsic_ssbo_atomic_fmin:
+   case nir_intrinsic_ssbo_atomic_fmax:
+   case nir_intrinsic_ssbo_atomic_fcomp_swap:
+      /* 0: SSBO index
+       * 1: offset
+       */
+      if (large_ssbo(state, intr->src[0]))
+         return lower_large_src(&intr->src[1], state);
+      return false;
+
+   case nir_intrinsic_global_atomic_add:
+   case nir_intrinsic_global_atomic_imin:
+   case nir_intrinsic_global_atomic_umin:
+   case nir_intrinsic_global_atomic_imax:
+   case nir_intrinsic_global_atomic_umax:
+   case nir_intrinsic_global_atomic_and:
+   case nir_intrinsic_global_atomic_or:
+   case nir_intrinsic_global_atomic_xor:
+   case nir_intrinsic_global_atomic_exchange:
+   case nir_intrinsic_global_atomic_comp_swap:
+   case nir_intrinsic_global_atomic_fadd:
+   case nir_intrinsic_global_atomic_fmin:
+   case nir_intrinsic_global_atomic_fmax:
+   case nir_intrinsic_global_atomic_fcomp_swap:
+      /* just assume we that 24b is not sufficient: */
+      return lower_large_src(&intr->src[0], state);
+
+   /* These should all be small enough to unconditionally use imul24: */
+   case nir_intrinsic_shared_atomic_add:
+   case nir_intrinsic_shared_atomic_imin:
+   case nir_intrinsic_shared_atomic_umin:
+   case nir_intrinsic_shared_atomic_imax:
+   case nir_intrinsic_shared_atomic_umax:
+   case nir_intrinsic_shared_atomic_and:
+   case nir_intrinsic_shared_atomic_or:
+   case nir_intrinsic_shared_atomic_xor:
+   case nir_intrinsic_shared_atomic_exchange:
+   case nir_intrinsic_shared_atomic_comp_swap:
+   case nir_intrinsic_shared_atomic_fadd:
+   case nir_intrinsic_shared_atomic_fmin:
+   case nir_intrinsic_shared_atomic_fmax:
+   case nir_intrinsic_shared_atomic_fcomp_swap:
+   case nir_intrinsic_load_uniform:
+   case nir_intrinsic_load_input:
+   case nir_intrinsic_load_output:
+   case nir_intrinsic_store_output:
+   default:
+      return false;
+   }
+}
+
+static bool
+lower_instr(lower_state *state, nir_instr *instr)
+{
+   bool progress = false;
+
+   if (instr->type == nir_instr_type_intrinsic) {
+      progress |= lower_intrinsic(state, nir_instr_as_intrinsic(instr));
+   }
+
+   return progress;
+}
+
+static bool
+is_large(lower_state *state, nir_variable *var)
+{
+   unsigned size = state->type_size(var->type, false);
+
+   /* if size is not known (ie. VLA) then assume the worst: */
+   if (!size)
+      return true;
+
+   return size >= (1 << 23);
+}
+
+bool
+nir_lower_amul(nir_shader *shader,
+               int (*type_size)(const struct glsl_type *, bool))
+{
+   assert(shader->options->has_imul24);
+   assert(type_size);
+
+   /* uniforms list actually includes ubo's and ssbo's: */
+   int num_uniforms = exec_list_length(&shader->uniforms);
+
+   NIR_VLA_FILL(bool, large_ubos, num_uniforms, 0);
+   NIR_VLA_FILL(bool, large_ssbos, num_uniforms, 0);
+
+   lower_state state = {
+         .type_size = type_size,
+         .large_ubos = large_ubos,
+         .large_ssbos = large_ssbos,
+   };
+
+   /* Figure out which UBOs or SSBOs are large enough to be
+    * disqualified from imul24:
+    */
+   nir_foreach_variable(var, &shader->uniforms) {
+      if (var->data.mode == nir_var_mem_ubo) {
+         assert(var->data.driver_location < num_uniforms);
+         if (is_large(&state, var)) {
+            state.has_large_ubo = true;
+            state.large_ubos[var->data.driver_location] = true;
+         }
+      } else if (var->data.mode == nir_var_mem_ssbo) {
+         assert(var->data.driver_location < num_uniforms);
+         if (is_large(&state, var)) {
+            state.has_large_ssbo = true;
+            state.large_ssbos[var->data.driver_location] = true;
+         }
+      }
+   }
+
+   /* clear pass flags: */
+   nir_foreach_function(function, shader) {
+      nir_function_impl *impl = function->impl;
+      if (!impl)
+         continue;
+
+      nir_foreach_block(block, impl) {
+         nir_foreach_instr(instr, block) {
+            instr->pass_flags = 0;
+         }
+      }
+   }
+
+   bool progress = false;
+   nir_foreach_function(function, shader) {
+      nir_function_impl *impl = function->impl;
+
+      if (!impl)
+         continue;
+
+      nir_foreach_block(block, impl) {
+         nir_foreach_instr(instr, block) {
+            progress |= lower_instr(&state, instr);
+         }
+      }
+   }
+
+   /* At this point, all 'amul's used in calculating an offset into
+    * a large variable have been replaced with 'imul'.  So remaining
+    * 'amul's can be replaced with 'imul24':
+    */
+   nir_foreach_function(function, shader) {
+      nir_function_impl *impl = function->impl;
+
+      if (!impl)
+         continue;
+
+      nir_foreach_block(block, impl) {
+         nir_foreach_instr(instr, block) {
+            if (instr->type != nir_instr_type_alu)
+               continue;
+
+            nir_alu_instr *alu = nir_instr_as_alu(instr);
+            if (alu->op != nir_op_amul)
+               continue;
+
+            alu->op = nir_op_imul24;
+            progress |= true;
+         }
+      }
+
+      nir_metadata_preserve(impl, nir_metadata_block_index |
+                                  nir_metadata_dominance);
+
+   }
+
+   return progress;
+}