nir/algebraic: optimize bits=umin(bits, 32-(offset&0x1f))

Optimizes patterns which are created by recent versions of vkd3d-proton,
when constant folding doesn't eliminate it entirely:
- ubitfield_extract(value, offset, umin(bits, 32-(offset&0x1f)))
- ibitfield_extract(value, offset, umin(bits, 32-(offset&0x1f)))
- bitfield_insert(base, insert, offset, umin(bits, 32-(offset&0x1f)))

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/13225>

src/compiler/nir/nir_opt_algebraic.py

@@ -1813,6 +1813,16 @@ optimizations.extend([
    (('bfm', 'bits', ('iand', 31, 'offset')), ('bfm', 'bits', 'offset')),
    (('bfm', ('iand', 31, 'bits'), 'offset'), ('bfm', 'bits', 'offset')),
 
+   # Optimizations for ubitfield_extract(value, offset, umin(bits, 32-(offset&0x1f))) and such
+   (('ult', a, ('umin', ('iand', a, b), c)), False),
+   (('ult', 31, ('umin', '#bits(is_ult_32)', a)), False),
+   (('ubfe', 'value', 'offset', ('umin', 'width', ('iadd', 32, ('ineg', ('iand', 31, 'offset'))))),
+    ('ubfe', 'value', 'offset', 'width')),
+   (('ibfe', 'value', 'offset', ('umin', 'width', ('iadd', 32, ('ineg', ('iand', 31, 'offset'))))),
+    ('ibfe', 'value', 'offset', 'width')),
+   (('bfm', ('umin', 'width', ('iadd', 32, ('ineg', ('iand', 31, 'offset')))), 'offset'),
+    ('bfm', 'width', 'offset')),
+
    # Section 8.8 (Integer Functions) of the GLSL 4.60 spec says:
    #
    #    If bits is zero, the result will be zero.

src/compiler/nir/nir_search_helpers.h

@@ -225,27 +225,44 @@ is_not_const_zero(UNUSED struct hash_table *ht, const nir_alu_instr *instr,
    return true;
 }
 
-/** Is value unsigned less than 0xfffc07fc? */
+/** Is value unsigned less than the limit? */
 static inline bool
-is_ult_0xfffc07fc(UNUSED struct hash_table *ht, const nir_alu_instr *instr,
-                  unsigned src, unsigned num_components,
-                  const uint8_t *swizzle)
+is_ult(const nir_alu_instr *instr, unsigned src, unsigned num_components, const uint8_t *swizzle,
+       uint64_t limit)
 {
    /* only constant srcs: */
    if (!nir_src_is_const(instr->src[src].src))
       return false;
 
    for (unsigned i = 0; i < num_components; i++) {
-      const unsigned val =
+      const uint64_t val =
          nir_src_comp_as_uint(instr->src[src].src, swizzle[i]);
 
-      if (val >= 0xfffc07fcU)
+      if (val >= limit)
          return false;
    }
 
    return true;
 }
 
+/** Is value unsigned less than 32? */
+static inline bool
+is_ult_32(UNUSED struct hash_table *ht, const nir_alu_instr *instr,
+          unsigned src, unsigned num_components,
+          const uint8_t *swizzle)
+{
+   return is_ult(instr, src, num_components, swizzle, 32);
+}
+
+/** Is value unsigned less than 0xfffc07fc? */
+static inline bool
+is_ult_0xfffc07fc(UNUSED struct hash_table *ht, const nir_alu_instr *instr,
+                  unsigned src, unsigned num_components,
+                  const uint8_t *swizzle)
+{
+   return is_ult(instr, src, num_components, swizzle, 0xfffc07fcU);
+}
+
 /** Is the first 5 bits of value unsigned greater than or equal 2? */
 static inline bool
 is_first_5_bits_uge_2(UNUSED struct hash_table *ht, const nir_alu_instr *instr,