nir/search: Add support for matching unknown constants

There are some algebraic transformations that we want to do but only if
certain things are constants.  For instance, we may want to replace
a * (b + c) with (a * b) + (a * c) as long as a and either b or c is constant.
While this generates more instructions, some of it will get constant
folded.

nir_algebraic.py doesn't handle this yet, but that's ok because the C
language will make sure that false is the default for now.

Reviewed-by: Kenneth Graunke <[email protected]>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/glsl/nir/nir_search.h b/src/glsl/nir/nir_search.h
index 8ec58b07139..18aa28dcc66 100644
--- a/src/glsl/nir/nir_search.h
+++ b/src/glsl/nir/nir_search.h
@@ -47,6 +47,13 @@ typedef struct {
 
    /** The variable index;  Must be less than NIR_SEARCH_MAX_VARIABLES */
    unsigned variable;
+
+   /** Indicates that the given variable must be a constant
+    *
+    * This is only alloed in search expressions and indicates that the
+    * given variable is only allowed to match constant values.
+    */
+   bool is_constant;
 } nir_search_variable;
 
 typedef struct {