nir/algebraic: add ignore_exact() wrapper

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13436>

4 files changed, 42 insertions, 7 deletions

diff --git a/src/compiler/nir/nir_algebraic.py b/src/compiler/nir/nir_algebraic.py
index bfe00d6ed85..9a4e8054345 100644
--- a/src/compiler/nir/nir_algebraic.py
+++ b/src/compiler/nir/nir_algebraic.py
@@ -98,13 +98,33 @@ class VarSet(object):
    def lock(self):
       self.immutable = True
 
+class SearchExpression(object):
+   def __init__(self, expr):
+      self.opcode = expr[0]
+      self.sources = expr[1:]
+      self.ignore_exact = False
+
+   @staticmethod
+   def create(val):
+      if isinstance(val, tuple):
+         return SearchExpression(val)
+      else:
+         assert(isinstance(val, SearchExpression))
+         return val
+
+   def __repr__(self):
+      l = [self.opcode, *self.sources]
+      if self.ignore_exact:
+         l.append('ignore_exact')
+      return repr((*l,))
+
 class Value(object):
    @staticmethod
    def create(val, name_base, varset, algebraic_pass):
       if isinstance(val, bytes):
          val = val.decode('utf-8')
 
-      if isinstance(val, tuple):
+      if isinstance(val, tuple) or isinstance(val, SearchExpression):
          return Expression(val, name_base, varset, algebraic_pass)
       elif isinstance(val, Expression):
          return val
@@ -185,7 +205,9 @@ class Value(object):
       ${val.cond_index},
       ${val.swizzle()},
 % elif isinstance(val, Expression):
-      ${'true' if val.inexact else 'false'}, ${'true' if val.exact else 'false'},
+      ${'true' if val.inexact else 'false'},
+      ${'true' if val.exact else 'false'},
+      ${'true' if val.ignore_exact else 'false'},
       ${val.c_opcode()},
       ${val.comm_expr_idx}, ${val.comm_exprs},
       { ${', '.join(src.array_index for src in val.sources)} },
@@ -339,15 +361,17 @@ _opcode_re = re.compile(r"(?P<inexact>~)?(?P<exact>!)?(?P<opcode>\w+)(?:@(?P<bit
 class Expression(Value):
    def __init__(self, expr, name_base, varset, algebraic_pass):
       Value.__init__(self, expr, name_base, "expression")
-      assert isinstance(expr, tuple)
 
-      m = _opcode_re.match(expr[0])
+      expr = SearchExpression.create(expr)
+
+      m = _opcode_re.match(expr.opcode)
       assert m and m.group('opcode') is not None
 
       self.opcode = m.group('opcode')
       self._bit_size = int(m.group('bits')) if m.group('bits') else None
       self.inexact = m.group('inexact') is not None
       self.exact = m.group('exact') is not None
+      self.ignore_exact = expr.ignore_exact
       self.cond = m.group('cond')
 
       assert not self.inexact or not self.exact, \
@@ -372,7 +396,7 @@ class Expression(Value):
       self.cond_index = get_cond_index(algebraic_pass.expression_cond, self.cond)
 
       self.sources = [ Value.create(src, "{0}_{1}".format(name_base, i), varset, algebraic_pass)
-                       for (i, src) in enumerate(expr[1:]) ]
+                       for (i, src) in enumerate(expr.sources) ]
 
       # nir_search_expression::srcs is hard-coded to 4
       assert len(self.sources) <= 4
@@ -1235,3 +1259,9 @@ class AlgebraicPass(object):
                                              variable_cond = sorted(self.variable_cond.items(), key=lambda kv: kv[1]),
                                              get_c_opcode=get_c_opcode,
                                              itertools=itertools)
+
+# The replacement expression isn't necessarily exact if the search expression is exact.
+def ignore_exact(*expr):
+   expr = SearchExpression.create(expr)
+   expr.ignore_exact = True
+   return expr
diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 949e0f24278..147e0dd345d 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -41,6 +41,8 @@ e = 'e'
 signed_zero_inf_nan_preserve_16 = 'nir_is_float_control_signed_zero_inf_nan_preserve(info->float_controls_execution_mode, 16)'
 signed_zero_inf_nan_preserve_32 = 'nir_is_float_control_signed_zero_inf_nan_preserve(info->float_controls_execution_mode, 32)'
 
+ignore_exact = nir_algebraic.ignore_exact
+
 # Written in the form (<search>, <replace>) where <search> is an expression
 # and <replace> is either an expression or a value.  An expression is
 # defined as a tuple of the form ([~]<op>, <src0>, <src1>, <src2>, <src3>)
diff --git a/src/compiler/nir/nir_search.c b/src/compiler/nir/nir_search.c
index 3246d13ec8a..4fd7ad66143 100644
--- a/src/compiler/nir/nir_search.c
+++ b/src/compiler/nir/nir_search.c
@@ -408,7 +408,7 @@ match_expression(const nir_algebraic_table *table, const nir_search_expression *
       return false;
 
    state->inexact_match = expr->inexact || state->inexact_match;
-   state->has_exact_alu = instr->exact || state->has_exact_alu;
+   state->has_exact_alu = (instr->exact && !expr->ignore_exact) || state->has_exact_alu;
    if (state->inexact_match && state->has_exact_alu)
       return false;
 
diff --git a/src/compiler/nir/nir_search.h b/src/compiler/nir/nir_search.h
index 2a7e9a2f0fe..fb56592cdd4 100644
--- a/src/compiler/nir/nir_search.h
+++ b/src/compiler/nir/nir_search.h
@@ -142,8 +142,11 @@ typedef struct {
    /** In a replacement, requests that the instruction be marked exact. */
    bool exact : 1;
 
+   /** Don't make the replacement exact if the search expression is exact. */
+   bool ignore_exact : 1;
+
    /* One of nir_op or nir_search_op */
-   uint16_t opcode : 14;
+   uint16_t opcode : 13;
 
    /* Commutative expression index.  This is assigned by opt_algebraic.py when
     * search structures are constructed and is a unique (to this structure)