nir: Add a basic constant folding pass

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

4 files changed, 283 insertions, 0 deletions

diff --git a/src/glsl/Makefile.sources b/src/glsl/Makefile.sources
index fe0f47b..604d9ed 100644
--- a/src/glsl/Makefile.sources
+++ b/src/glsl/Makefile.sources
@@ -36,6 +36,7 @@ NIR_FILES = \
 	$(GLSL_SRCDIR)/nir/nir_metadata.c \
 	$(GLSL_SRCDIR)/nir/nir_opcodes.c \
 	$(GLSL_SRCDIR)/nir/nir_opcodes.h \
+	$(GLSL_SRCDIR)/nir/nir_opt_constant_folding.c \
 	$(GLSL_SRCDIR)/nir/nir_opt_copy_propagate.c \
 	$(GLSL_SRCDIR)/nir/nir_opt_cse.c \
 	$(GLSL_SRCDIR)/nir/nir_opt_dce.c \
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index f3845f9..0c21dca 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1399,6 +1399,7 @@ void nir_convert_to_ssa(nir_shader *shader);
 void nir_convert_from_ssa(nir_shader *shader);
 
 bool nir_opt_algebraic(nir_shader *shader);
+bool nir_opt_constant_folding(nir_shader *shader);
 
 bool nir_opt_global_to_local(nir_shader *shader);
 
diff --git a/src/glsl/nir/nir_opt_constant_folding.c b/src/glsl/nir/nir_opt_constant_folding.c
new file mode 100644
index 0000000..61f6723
--- /dev/null
+++ b/src/glsl/nir/nir_opt_constant_folding.c
@@ -0,0 +1,279 @@
+/*
+ * Copyright © 2014 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.
+ *
+ * Authors:
+ *    Jason Ekstrand (jason@jlekstrand.net)
+ *
+ */
+
+#include "nir.h"
+#include <math.h>
+
+/*
+ * Implements SSA-based constant folding.
+ */
+
+struct constant_fold_state {
+   void *mem_ctx;
+   nir_function_impl *impl;
+   bool progress;
+};
+
+#define SRC_COMP(T, IDX, CMP) src[IDX]->value.T[instr->src[IDX].swizzle[CMP]]
+#define SRC(T, IDX) SRC_COMP(T, IDX, i)
+#define DEST_COMP(T, CMP) dest->value.T[CMP]
+#define DEST(T) DEST_COMP(T, i)
+
+#define FOLD_PER_COMP(EXPR) \
+   for (unsigned i = 0; i < instr->dest.dest.ssa.num_components; i++) { \
+      EXPR; \
+   } \
+
+static bool
+constant_fold_alu_instr(nir_alu_instr *instr, void *void_state)
+{
+   struct constant_fold_state *state = void_state;
+   nir_load_const_instr *src[4], *dest;
+
+   if (!instr->dest.dest.is_ssa)
+      return false;
+
+   for (unsigned i = 0; i < nir_op_infos[instr->op].num_inputs; i++) {
+      if (!instr->src[i].src.is_ssa)
+         return false;
+
+      if (instr->src[i].src.ssa->parent_instr->type != nir_instr_type_load_const)
+         return false;
+
+      /* We shouldn't have any source modifiers in the optimization loop. */
+      assert(!instr->src[i].abs && !instr->src[i].negate);
+
+      src[i] = nir_instr_as_load_const(instr->src[i].src.ssa->parent_instr);
+   }
+
+   /* We shouldn't have any saturate modifiers in the optimization loop. */
+   assert(!instr->dest.saturate);
+
+   dest = nir_load_const_instr_create(state->mem_ctx);
+   dest->array_elems = 0;
+   dest->num_components = instr->dest.dest.ssa.num_components;
+
+   switch (instr->op) {
+   case nir_op_ineg:
+      FOLD_PER_COMP(DEST(i) = -SRC(i, 0));
+      break;
+   case nir_op_fneg:
+      FOLD_PER_COMP(DEST(f) = -SRC(f, 0));
+      break;
+   case nir_op_inot:
+      FOLD_PER_COMP(DEST(i) = ~SRC(i, 0));
+      break;
+   case nir_op_fnot:
+      FOLD_PER_COMP(DEST(f) = (SRC(f, 0) == 0.0f) ? 1.0f : 0.0f);
+      break;
+   case nir_op_frcp:
+      FOLD_PER_COMP(DEST(f) = 1.0f / SRC(f, 0));
+      break;
+   case nir_op_frsq:
+      FOLD_PER_COMP(DEST(f) = 1.0f / sqrt(SRC(f, 0)));
+      break;
+   case nir_op_fsqrt:
+      FOLD_PER_COMP(DEST(f) = sqrtf(SRC(f, 0)));
+      break;
+   case nir_op_fexp:
+      FOLD_PER_COMP(DEST(f) = expf(SRC(f, 0)));
+      break;
+   case nir_op_flog:
+      FOLD_PER_COMP(DEST(f) = logf(SRC(f, 0)));
+      break;
+   case nir_op_fexp2:
+      FOLD_PER_COMP(DEST(f) = exp2f(SRC(f, 0)));
+      break;
+   case nir_op_flog2:
+      FOLD_PER_COMP(DEST(f) = log2f(SRC(f, 0)));
+      break;
+   case nir_op_f2i:
+      FOLD_PER_COMP(DEST(i) = SRC(f, 0));
+      break;
+   case nir_op_f2u:
+      FOLD_PER_COMP(DEST(u) = SRC(f, 0));
+      break;
+   case nir_op_i2f:
+      FOLD_PER_COMP(DEST(f) = SRC(i, 0));
+      break;
+   case nir_op_f2b:
+      FOLD_PER_COMP(DEST(u) = (SRC(i, 0) == 0.0f) ? NIR_FALSE : NIR_TRUE);
+      break;
+   case nir_op_b2f:
+      FOLD_PER_COMP(DEST(f) = SRC(u, 0) ? 1.0f : 0.0f);
+      break;
+   case nir_op_i2b:
+      FOLD_PER_COMP(DEST(u) = SRC(i, 0) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_u2f:
+      FOLD_PER_COMP(DEST(f) = SRC(u, 0));
+      break;
+   case nir_op_bany2:
+      DEST_COMP(u, 0) = (SRC_COMP(u, 0, 0) || SRC_COMP(u, 0, 1)) ?
+                        NIR_TRUE : NIR_FALSE;
+      break;
+   case nir_op_fadd:
+      FOLD_PER_COMP(DEST(f) = SRC(f, 0) + SRC(f, 1));
+      break;
+   case nir_op_iadd:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) + SRC(i, 1));
+      break;
+   case nir_op_fsub:
+      FOLD_PER_COMP(DEST(f) = SRC(f, 0) - SRC(f, 1));
+      break;
+   case nir_op_isub:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) - SRC(i, 1));
+      break;
+   case nir_op_fmul:
+      FOLD_PER_COMP(DEST(f) = SRC(f, 0) * SRC(f, 1));
+      break;
+   case nir_op_imul:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) * SRC(i, 1));
+      break;
+   case nir_op_fdiv:
+      FOLD_PER_COMP(DEST(f) = SRC(f, 0) / SRC(f, 1));
+      break;
+   case nir_op_idiv:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) / SRC(i, 1));
+      break;
+   case nir_op_udiv:
+      FOLD_PER_COMP(DEST(u) = SRC(u, 0) / SRC(u, 1));
+      break;
+   case nir_op_flt:
+      FOLD_PER_COMP(DEST(u) = (SRC(f, 0) < SRC(f, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_fge:
+      FOLD_PER_COMP(DEST(u) = (SRC(f, 0) >= SRC(f, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_feq:
+      FOLD_PER_COMP(DEST(u) = (SRC(f, 0) == SRC(f, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_fne:
+      FOLD_PER_COMP(DEST(u) = (SRC(f, 0) != SRC(f, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_ilt:
+      FOLD_PER_COMP(DEST(u) = (SRC(i, 0) < SRC(i, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_ige:
+      FOLD_PER_COMP(DEST(u) = (SRC(i, 0) >= SRC(i, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_ieq:
+      FOLD_PER_COMP(DEST(u) = (SRC(i, 0) == SRC(i, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_ine:
+      FOLD_PER_COMP(DEST(u) = (SRC(i, 0) != SRC(i, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_ult:
+      FOLD_PER_COMP(DEST(u) = (SRC(u, 0) < SRC(u, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_uge:
+      FOLD_PER_COMP(DEST(u) = (SRC(u, 0) >= SRC(u, 1)) ? NIR_TRUE : NIR_FALSE);
+      break;
+   case nir_op_ishl:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) << SRC(i, 1));
+      break;
+   case nir_op_ishr:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) >> SRC(i, 1));
+      break;
+   case nir_op_ushr:
+      FOLD_PER_COMP(DEST(u) = SRC(u, 0) >> SRC(u, 1));
+      break;
+   case nir_op_iand:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) & SRC(i, 1));
+      break;
+   case nir_op_ior:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) | SRC(i, 1));
+      break;
+   case nir_op_ixor:
+      FOLD_PER_COMP(DEST(i) = SRC(i, 0) ^ SRC(i, 1));
+      break;
+   default:
+      ralloc_free(dest);
+      return false;
+   }
+
+   dest->dest.is_ssa = true;
+   nir_ssa_def_init(&dest->instr, &dest->dest.ssa,
+                    instr->dest.dest.ssa.num_components,
+                    instr->dest.dest.ssa.name);
+
+   nir_instr_insert_before(&instr->instr, &dest->instr);
+
+   nir_src new_src = {
+      .is_ssa = true,
+      .ssa = &dest->dest.ssa,
+   };
+
+   nir_ssa_def_rewrite_uses(&instr->dest.dest.ssa, new_src, state->mem_ctx);
+
+   nir_instr_remove(&instr->instr);
+   ralloc_free(instr);
+
+   return true;
+}
+
+static bool
+constant_fold_block(nir_block *block, void *void_state)
+{
+   struct constant_fold_state *state = void_state;
+
+   nir_foreach_instr_safe(block, instr) {
+      if (instr->type != nir_instr_type_alu)
+         continue;
+
+      state->progress |= constant_fold_alu_instr(nir_instr_as_alu(instr), state);
+   }
+
+   return true;
+}
+
+static bool
+nir_opt_constant_folding_impl(nir_function_impl *impl)
+{
+   struct constant_fold_state state;
+
+   state.mem_ctx = ralloc_parent(impl);
+   state.impl = impl;
+   state.progress = false;
+
+   nir_foreach_block(impl, constant_fold_block, &state);
+
+   return state.progress;
+}
+
+bool
+nir_opt_constant_folding(nir_shader *shader)
+{
+   bool progress = false;
+
+   nir_foreach_overload(shader, overload) {
+      if (overload->impl)
+         progress |= nir_opt_constant_folding_impl(overload->impl);
+   }
+
+   return progress;
+}
diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
index 120bd5c..b712085 100644
--- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
@@ -55,6 +55,8 @@ fs_visitor::emit_nir_code()
       nir_validate_shader(nir);
       progress |= nir_opt_algebraic(nir);
       nir_validate_shader(nir);
+      progress |= nir_opt_constant_folding(nir);
+      nir_validate_shader(nir);
    } while (progress);
 
    /* Lower a bunch of stuff */