glsl: Drop borrow/carry lowerings in favor of nir

Unconditionally lowering prevents GL drivers from natively
implementing these ops. Drivers that need lowering should set
lower_uadd_carry and lower_usub_borrow on nir_shader_compiler_options to
get the nir lowerings.

Tested with dEQP-GLES31.functional.shaders.builtin_functions.integer.*

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19704>

src/compiler/glsl/lower_instructions.cpp

@@ -89,8 +89,6 @@ private:
    void dldexp_to_arith(ir_expression *);
    void dfrexp_sig_to_arith(ir_expression *);
    void dfrexp_exp_to_arith(ir_expression *);
-   void carry_to_arith(ir_expression *);
-   void borrow_to_arith(ir_expression *);
    void double_dot_to_fma(ir_expression *);
    void double_lrp(ir_expression *);
    void dceil_to_dfrac(ir_expression *);
@@ -580,44 +578,6 @@ lower_instructions_visitor::dfrexp_exp_to_arith(ir_expression *ir)
    this->progress = true;
 }
 
-void
-lower_instructions_visitor::carry_to_arith(ir_expression *ir)
-{
-   /* Translates
-    *   ir_binop_carry x y
-    * into
-    *   sum = ir_binop_add x y
-    *   bcarry = ir_binop_less sum x
-    *   carry = ir_unop_b2i bcarry
-    */
-
-   ir_rvalue *x_clone = ir->operands[0]->clone(ir, NULL);
-   ir->operation = ir_unop_i2u;
-   ir->init_num_operands();
-   ir->operands[0] = b2i(less(add(ir->operands[0], ir->operands[1]), x_clone));
-   ir->operands[1] = NULL;
-
-   this->progress = true;
-}
-
-void
-lower_instructions_visitor::borrow_to_arith(ir_expression *ir)
-{
-   /* Translates
-    *   ir_binop_borrow x y
-    * into
-    *   bcarry = ir_binop_less x y
-    *   carry = ir_unop_b2i bcarry
-    */
-
-   ir->operation = ir_unop_i2u;
-   ir->init_num_operands();
-   ir->operands[0] = b2i(less(ir->operands[0], ir->operands[1]));
-   ir->operands[1] = NULL;
-
-   this->progress = true;
-}
-
 void
 lower_instructions_visitor::double_dot_to_fma(ir_expression *ir)
 {
@@ -1467,14 +1427,6 @@ lower_instructions_visitor::visit_leave(ir_expression *ir)
          dfrexp_sig_to_arith(ir);
       break;
 
-   case ir_binop_carry:
-      carry_to_arith(ir);
-      break;
-
-   case ir_binop_borrow:
-      borrow_to_arith(ir);
-      break;
-
    case ir_unop_trunc:
       if (lowering(DOPS_TO_DFRAC) && ir->type->is_double())
          dtrunc_to_dfrac(ir);

src/gallium/auxiliary/nir/nir_to_tgsi.c

@@ -3656,6 +3656,8 @@ ntt_fix_nir_options(struct pipe_screen *screen, struct nir_shader *s,
        !options->lower_flrp64 ||
        !options->lower_fmod ||
        !options->lower_rotate ||
+       !options->lower_uadd_carry ||
+       !options->lower_usub_borrow ||
        !options->lower_uadd_sat ||
        !options->lower_usub_sat ||
        !options->lower_uniforms_to_ubo ||
@@ -3674,6 +3676,8 @@ ntt_fix_nir_options(struct pipe_screen *screen, struct nir_shader *s,
       new_options->lower_flrp64 = true;
       new_options->lower_fmod = true;
       new_options->lower_rotate = true;
+      new_options->lower_uadd_carry = true;
+      new_options->lower_usub_borrow = true;
       new_options->lower_uadd_sat = true;
       new_options->lower_usub_sat = true;
       new_options->lower_uniforms_to_ubo = true;
@@ -4030,6 +4034,8 @@ static const nir_shader_compiler_options nir_to_tgsi_compiler_options = {
    .lower_fmod = true,
    .lower_rotate = true,
    .lower_uniforms_to_ubo = true,
+   .lower_uadd_carry = true,
+   .lower_usub_borrow = true,
    .lower_uadd_sat = true,
    .lower_usub_sat = true,
    .lower_vector_cmp = true,

src/gallium/drivers/etnaviv/etnaviv_compiler.c

@@ -42,6 +42,7 @@ etna_compiler_create(const char *renderer, const struct etna_specs *specs)
       .fuse_ffma32 = true,
       .fuse_ffma64 = true,
       .lower_uadd_carry = true,
+      .lower_usub_borrow = true,
       .lower_mul_high = true,
       .lower_bitops = true,
       .lower_all_io_to_temps = true,

src/gallium/drivers/r600/r600_pipe_common.c

@@ -1334,6 +1334,8 @@ bool r600_common_screen_init(struct r600_common_screen *rscreen,
 		.lower_isign = true,
 		.lower_fsign = true,
 		.lower_fmod = true,
+		.lower_uadd_carry = true,
+		.lower_usub_borrow = true,
 		.lower_extract_byte = true,
 		.lower_extract_word = true,
 		.lower_insert_byte = true,

src/gallium/drivers/zink/zink_compiler.c

@@ -338,6 +338,7 @@ zink_screen_init_compiler(struct zink_screen *screen)
       .lower_mul_high = true,
       .lower_rotate = true,
       .lower_uadd_carry = true,
+      .lower_usub_borrow = true,
       .lower_uadd_sat = true,
       .lower_usub_sat = true,
       .lower_vector_cmp = true,

src/microsoft/compiler/nir_to_dxil.c

@@ -115,6 +115,7 @@ nir_options = {
    .lower_usub_sat = true,
    .lower_iadd_sat = true,
    .lower_uadd_carry = true,
+   .lower_usub_borrow = true,
    .lower_mul_high = true,
    .lower_rotate = true,
    .lower_pack_half_2x16 = true,

src/panfrost/midgard/midgard_compile.h

@@ -55,6 +55,8 @@ static const nir_shader_compiler_options midgard_nir_options = {
         .lower_find_lsb = true,
         .lower_ifind_msb = true,
         .lower_fdph = true,
+        .lower_uadd_carry = true,
+        .lower_usub_borrow = true,
 
         /* TODO: We have native ops to help here, which we'll want to look into
          * eventually */