--- /dev/null
+/*
+ * Copyright (C) 2020 Collabora Ltd.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "compiler.h"
+#include "bi_builder.h"
+
+/* Dead simple constant folding to cleanup compiler frontend patterns. Before
+ * adding a new pattern here, check why you need it and whether we can avoid
+ * generating the constant BIR at all. */
+
+static uint32_t
+bi_fold_constant(bi_instr *I, bool *unsupported)
+{
+ uint32_t a = I->src[0].value;
+ uint32_t b = I->src[1].value;
+
+ switch (I->op) {
+ case BI_OPCODE_SWZ_V2I16:
+ {
+ uint16_t lo = (a & 0xFFFF);
+ uint16_t hi = (a >> 16);
+
+ enum bi_swizzle swz = I->src[0].swizzle;
+ assert(swz < BI_SWIZZLE_H11);
+
+ /* Note order is H00, H01, H10, H11 */
+ return (((swz & (1 << 1)) ? hi : lo) << 0) |
+ (((swz & (1 << 0)) ? hi : lo) << 16);
+ }
+
+ case BI_OPCODE_MKVEC_V2I16:
+ {
+ bool hi_a = I->src[0].swizzle & BI_SWIZZLE_H11;
+ bool hi_b = I->src[1].swizzle & BI_SWIZZLE_H11;
+
+ uint16_t lo = (hi_a ? (a >> 16) : (a & 0xFFFF));
+ uint16_t hi = (hi_b ? (b >> 16) : (b & 0xFFFF));
+
+ return (hi << 16) | lo;
+ }
+
+ default:
+ *unsupported = true;
+ return 0;
+ }
+}
+
+static bool
+bi_all_srcs_const(bi_instr *I)
+{
+ bi_foreach_src(I, s) {
+ enum bi_index_type type = I->src[s].type;
+
+ if (!(type == BI_INDEX_NULL || type == BI_INDEX_CONSTANT))
+ return false;
+ }
+
+ return true;
+}
+
+void
+bi_opt_constant_fold(bi_context *ctx)
+{
+ bi_foreach_instr_global_safe(ctx, ins) {
+ if (!bi_all_srcs_const(ins)) continue;
+
+ bool unsupported = false;
+ uint32_t replace = bi_fold_constant(ins, &unsupported);
+ if (unsupported) continue;
+
+ /* Replace with constant move, to be copypropped */
+ bi_builder b = bi_init_builder(ctx, bi_after_instr(ins));
+ bi_mov_i32_to(&b, ins->dest[0], bi_imm_u32(replace));
+ bi_remove_instruction(ins);
+ }
+}