nir: propagate bitsize information in nir_search

When we replace an expresion we have to compute bitsize information for the
replacement. We do this in two passes to validate that bitsize information
is consistent and correct: first we propagate bitsize from child nodes to
parent, then we do it the other way around, starting from the original's
instruction destination bitsize.

v2 (Iago):
- Always use nir_type_bool32 instead of nir_type_bool when generating
  algebraic optimizations. Before we used nir_type_bool32 with constants
  and nir_type_bool with variables.
- Fix bool comparisons in nir_search.c to account for bitsized types.

v3 (Sam):
- Unpack the double constant value as unsigned long long (8 bytes) in
nir_algrebraic.py.

v4 (Sam):
- Use helpers to get type size and base type from nir_alu_type.

Signed-off-by: Iago Toral Quiroga <itoral@igalia.com>
Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>

src/compiler/nir/nir_search.h

@@ -71,10 +71,12 @@ typedef struct {
 typedef struct {
    nir_search_value value;
 
+   nir_alu_type type;
+
    union {
-      uint32_t u;
-      int32_t i;
-      float f;
+      uint64_t u;
+      int64_t i;
+      double d;
    } data;
 } nir_search_constant;