diff options
| -rw-r--r-- | src/mesa/drivers/dri/i965/brw_vec4.cpp | 98 | ||||
| -rw-r--r-- | src/mesa/drivers/dri/i965/brw_vec4.h | 1 |
2 files changed, 99 insertions, 0 deletions
diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp b/src/mesa/drivers/dri/i965/brw_vec4.cpp index bfb0fba3987..5477fe6ab5f 100644 --- a/src/mesa/drivers/dri/i965/brw_vec4.cpp +++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp @@ -311,6 +311,103 @@ src_reg::equals(const src_reg &r) const sizeof(fixed_hw_reg)) == 0); } +/* Replaces unused channels of a swizzle with channels that are used. + * + * For instance, this pass transforms + * + * mov vgrf4.yz, vgrf5.wxzy + * + * into + * + * mov vgrf4.yz, vgrf5.xxzx + * + * This eliminates false uses of some channels, letting dead code elimination + * remove the instructions that wrote them. + */ +bool +vec4_visitor::opt_reduce_swizzle() +{ + bool progress = false; + + foreach_in_list_safe(vec4_instruction, inst, &instructions) { + if (inst->dst.file == BAD_FILE || inst->dst.file == HW_REG) + continue; + + int swizzle[4]; + + /* Determine which channels of the sources are read. */ + switch (inst->opcode) { + case BRW_OPCODE_DP4: + case BRW_OPCODE_DPH: /* FINISHME: DPH reads only three channels of src0, + * but all four of src1. + */ + swizzle[0] = 0; + swizzle[1] = 1; + swizzle[2] = 2; + swizzle[3] = 3; + break; + case BRW_OPCODE_DP3: + swizzle[0] = 0; + swizzle[1] = 1; + swizzle[2] = 2; + swizzle[3] = -1; + break; + case BRW_OPCODE_DP2: + swizzle[0] = 0; + swizzle[1] = 1; + swizzle[2] = -1; + swizzle[3] = -1; + break; + default: + swizzle[0] = inst->dst.writemask & WRITEMASK_X ? 0 : -1; + swizzle[1] = inst->dst.writemask & WRITEMASK_Y ? 1 : -1; + swizzle[2] = inst->dst.writemask & WRITEMASK_Z ? 2 : -1; + swizzle[3] = inst->dst.writemask & WRITEMASK_W ? 3 : -1; + break; + } + + /* Resolve unread channels (-1) by assigning them the swizzle of the + * first channel that is used. + */ + int first_used_channel = 0; + for (int i = 0; i < 4; i++) { + if (swizzle[i] != -1) { + first_used_channel = swizzle[i]; + break; + } + } + for (int i = 0; i < 4; i++) { + if (swizzle[i] == -1) { + swizzle[i] = first_used_channel; + } + } + + /* Update sources' swizzles. */ + for (int i = 0; i < 3; i++) { + if (inst->src[i].file != GRF && + inst->src[i].file != ATTR && + inst->src[i].file != UNIFORM) + continue; + + int swiz[4]; + for (int j = 0; j < 4; j++) { + swiz[j] = BRW_GET_SWZ(inst->src[i].swizzle, swizzle[j]); + } + + unsigned new_swizzle = BRW_SWIZZLE4(swiz[0], swiz[1], swiz[2], swiz[3]); + if (inst->src[i].swizzle != new_swizzle) { + inst->src[i].swizzle = new_swizzle; + progress = true; + } + } + } + + if (progress) + invalidate_live_intervals(); + + return progress; +} + static bool try_eliminate_instruction(vec4_instruction *inst, int new_writemask, const struct brw_context *brw) @@ -1699,6 +1796,7 @@ vec4_visitor::run() iteration++; int pass_num = 0; + OPT(opt_reduce_swizzle); OPT(dead_code_eliminate); OPT(dead_control_flow_eliminate, this); OPT(opt_copy_propagation); diff --git a/src/mesa/drivers/dri/i965/brw_vec4.h b/src/mesa/drivers/dri/i965/brw_vec4.h index 517eab13c1b..f0239cb998a 100644 --- a/src/mesa/drivers/dri/i965/brw_vec4.h +++ b/src/mesa/drivers/dri/i965/brw_vec4.h @@ -380,6 +380,7 @@ public: void calculate_live_intervals(); void invalidate_live_intervals(); void split_virtual_grfs(); + bool opt_reduce_swizzle(); bool dead_code_eliminate(); bool virtual_grf_interferes(int a, int b); bool opt_copy_propagation(); |