nir: Make bcsel a fully vector operation

Previously, the condition was a scalar that applied to all components
simultaneously.  As of this commit, the condition is a vector and each
component is switched seperately.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

src/glsl/nir/nir_lower_variables.c

@@ -836,6 +836,7 @@ lower_deref_to_ssa_block(nir_block *block, void *void_state)
                mov = nir_alu_instr_create(state->mem_ctx, nir_op_bcsel);
                mov->src[0].src = nir_src_copy(intrin->predicate,
                                               state->mem_ctx);
+               /* Splat the condition to all channels */
                memset(mov->src[0].swizzle, 0, sizeof mov->src[0].swizzle);
 
                mov->src[1].src.is_ssa = true;

src/glsl/nir/nir_opcodes.h

@@ -325,9 +325,8 @@ TRIOP(flrp, nir_type_float)
  * bools (0.0 vs 1.0) and one for integer bools (0 vs ~0).
  */
 
-OPCODE(fcsel, 3, true, 0, nir_type_float, ARR(1, 0, 0),
-       ARR(nir_type_float, nir_type_float, nir_type_float))
-OPCODE(bcsel, 3, true, 0, nir_type_unsigned, ARR(1, 0, 0),
+TRIOP(fcsel, nir_type_float)
+OPCODE(bcsel, 3, true, 0, nir_type_unsigned, ARR(0, 0, 0),
        ARR(nir_type_bool, nir_type_unsigned, nir_type_unsigned))
 
 TRIOP(bfi, nir_type_unsigned)

src/glsl/nir/nir_opt_peephole_select.c

@@ -136,6 +136,8 @@ nir_opt_peephole_select_block(nir_block *block, void *void_state)
       nir_phi_instr *phi = nir_instr_as_phi(instr);
       nir_alu_instr *sel = nir_alu_instr_create(state->mem_ctx, nir_op_bcsel);
       sel->src[0].src = nir_src_copy(if_stmt->condition, state->mem_ctx);
+      /* Splat the condition to all channels */
+      memset(sel->src[0].swizzle, 0, sizeof sel->src[0].swizzle);
 
       assert(exec_list_length(&phi->srcs) == 2);
       foreach_list_typed(nir_phi_src, src, node, &phi->srcs) {

src/glsl/nir/nir_to_ssa.c

@@ -235,6 +235,8 @@ rewrite_def_forwards(nir_dest *dest, void *_state)
       csel->dest.dest.reg.reg = dest->reg.reg;
       csel->dest.write_mask = (1 << dest->reg.reg->num_components) - 1;
       csel->src[0].src = nir_src_copy(*state->predicate, state->mem_ctx);
+      /* Splat the condition to all channels */
+      memset(csel->src[0].swizzle, 0, sizeof csel->src[0].swizzle);
       csel->src[2].src.is_ssa = true;
       csel->src[2].src.ssa = get_ssa_src(dest->reg.reg, state);
    }

src/mesa/drivers/dri/i965/brw_fs_nir.cpp

@@ -965,9 +965,14 @@ fs_visitor::nir_emit_alu(nir_alu_instr *instr)
       break;
 
    case nir_op_bcsel:
-      emit(CMP(reg_null_d, op[0], fs_reg(0), BRW_CONDITIONAL_NZ));
-      emit_percomp(BRW_OPCODE_SEL, result, op[1], op[2],
-                   instr->dest.write_mask, false, BRW_PREDICATE_NORMAL);
+      for (unsigned i = 0; i < 4; i++) {
+         if (!((instr->dest.write_mask >> i) & 1))
+            continue;
+
+         emit(CMP(reg_null_d, offset(op[0], i), fs_reg(0), BRW_CONDITIONAL_NZ));
+         emit(SEL(offset(result, i), offset(op[1], i), offset(op[2], i)))
+             ->predicate = BRW_PREDICATE_NORMAL;
+      }
       break;
 
    default: