<div dir="ltr">On 3 October 2013 10:59, Matt Turner <<a href="mailto:mattst88@gmail.com" target="_blank">mattst88@gmail.com</a>> wrote: <div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> <div class="im">v2: Check fixed_hw_reg.{file,nr} instead of dst.reg. </div>v3: Store the bool emitted_addc_or_subb in the class, not static. --- src/mesa/drivers/dri/i965/brw_fs.h | 3 + src/mesa/drivers/dri/i965/brw_fs_visitor.cpp | 104 +++++++++++++++++++++++++++ 2 files changed, 107 insertions(+) </blockquote><div> </div><div>Reviewed-by: Paul Berry <<a href="mailto:stereotype441@gmail.com">stereotype441@gmail.com</a>> </div><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> diff --git a/src/mesa/drivers/dri/i965/brw_fs.h b/src/mesa/drivers/dri/i965/brw_fs.h index 6a53e59..c703c2b 100644 <div class="im">--- a/src/mesa/drivers/dri/i965/brw_fs.h +++ b/src/mesa/drivers/dri/i965/brw_fs.h @@ -345,6 +345,7 @@ public: fs_reg src0, fs_reg src1); bool try_emit_saturate(ir_expression *ir); bool try_emit_mad(ir_expression *ir, int mul_arg); + void try_combine_add_with_addc_subb(); void try_replace_with_sel(); void emit_bool_to_cond_code(ir_rvalue *condition); void emit_if_gen6(ir_if *ir); </div>@@ -458,6 +459,8 @@ public: int force_uncompressed_stack; int force_sechalf_stack; + + bool emitted_addc_or_subb; }; /** diff --git a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp index b8c30e6..8accbd6 100644 --- a/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp +++ b/src/mesa/drivers/dri/i965/brw_fs_visitor.cpp @@ -313,6 +313,102 @@ fs_visitor::try_emit_mad(ir_expression *ir, int mul_arg) <div><div class="h5"> return true; } +/** + * The addition and carry in the uaddCarry() built-in function are implemented + * separately as ir_binop_add and ir_binop_carry respectively. i965 generates + * ADDC and a MOV from the accumulator for the carry. + * + * The generated code for uaddCarry(uint x, uint y, out uint carry) would look + * like this: + * + * addc null, x, y + * mov carry, acc0 + * add sum, x, y + * + * This peephole pass optimizes this into + * + * addc sum, x, y + * mov carry, acc0 + * + * usubBorrow() works in the same fashion. + */ +void +fs_visitor::try_combine_add_with_addc_subb() +{ + /* ADDC/SUBB was introduced in gen7. */ + if (brw->gen < 7) + return; + + fs_inst *add_inst = (fs_inst *) instructions.get_tail(); + assert(add_inst->opcode == BRW_OPCODE_ADD); + + /* ADDC/SUBB only operates on UD. */ + if (add_inst->dst.type != BRW_REGISTER_TYPE_UD || + add_inst->src[0].type != BRW_REGISTER_TYPE_UD || + add_inst->src[1].type != BRW_REGISTER_TYPE_UD) + return; + + bool found = false; + fs_inst *match = (fs_inst *) add_inst->prev; + /* The ADDC should appear within 8 instructions of ADD for a vec4. SUBB + * should appear farther away because of the extra MOV negates. + */ + for (int i = 0; i < 16; i++, match = (fs_inst *) match->prev) { + if (match->is_head_sentinel()) + return; + + /* Look for an ADDC/SUBB instruction whose destination is the null + * register (ir_binop_carry emits ADDC with null destination; same for + * ir_binop_borrow with SUBB) and whose sources are identical to those + * of the ADD. + */ + if (match->opcode != BRW_OPCODE_ADDC && match->opcode != BRW_OPCODE_SUBB) + continue; + + /* Only look for newly emitted ADDC/SUBB with null destination. */ + if (match->dst.file != HW_REG || + match->dst.fixed_hw_reg.file != BRW_ARCHITECTURE_REGISTER_FILE || + match-><a href="http://dst.fixed_hw_reg.nr" target="_blank">dst.fixed_hw_reg.nr</a> != BRW_ARF_NULL) + continue; + + fs_reg *src0 = &add_inst->src[0]; + fs_reg *src1 = &add_inst->src[1]; + + /* For SUBB, the ADD's second source will contain a negate modifier + * which at this point will be in the form of a + * + * MOV dst, -src + * + * instruction, so src[1].file will be GRF, even if it's a uniform push + * constant. + */ + if (match->src[1].reg != add_inst->src[1].reg) { + /* The negating MOV should be immediately before the ADD. */ + fs_inst *mov_inst = (fs_inst *) add_inst->prev; + if (mov_inst->opcode != BRW_OPCODE_MOV) + continue; + + src1 = &mov_inst->src[0]; + } + + /* If everything matches, we're done. */ + if (match->src[0].file == src0->file && + match->src[1].file == src1->file && + match->src[0].reg == src0->reg && + match->src[1].reg == src1->reg && + match->src[0].reg_offset == src0->reg_offset && + match->src[1].reg_offset == src1->reg_offset) { + found = true; + break; + } + } + + if (found) { + match->dst = add_inst->dst; + add_inst->remove(); + } +} + void fs_visitor::visit(ir_expression *ir) { </div></div>@@ -415,6 +511,8 @@ fs_visitor::visit(ir_expression *ir) <div class="im"> case ir_binop_add: emit(ADD(this->result, op[0], op[1])); + if (emitted_addc_or_subb) + try_combine_add_with_addc_subb(); break; case ir_binop_sub: assert(!"not reached: should be handled by ir_sub_to_add_neg"); </div>@@ -451,6 +549,8 @@ fs_visitor::visit(ir_expression *ir) <div class="im"> if (brw->gen >= 7 && dispatch_width == 16) fail("16-wide explicit accumulator operands unsupported\n"); + emitted_addc_or_subb = true; + struct brw_reg acc = retype(brw_acc_reg(), BRW_REGISTER_TYPE_UD); emit(ADDC(reg_null_ud, op[0], op[1])); </div>@@ -461,6 +561,8 @@ fs_visitor::visit(ir_expression *ir) <div class="im"> if (brw->gen >= 7 && dispatch_width == 16) fail("16-wide explicit accumulator operands unsupported\n"); + emitted_addc_or_subb = true; + struct brw_reg acc = retype(brw_acc_reg(), BRW_REGISTER_TYPE_UD); emit(SUBB(reg_null_ud, op[0], op[1])); </div>@@ -2610,6 +2712,8 @@ fs_visitor::fs_visitor(struct brw_context *brw, this->force_uncompressed_stack = 0; this->force_sechalf_stack = 0; + this->emitted_addc_or_subb = false; + memset(&this->param_size, 0, sizeof(this->param_size)); <div class="HOEnZb"><div class="h5"> } -- 1.8.3.2 _______________________________________________ mesa-dev mailing list <a href="mailto:mesa-dev@lists.freedesktop.org">mesa-dev@lists.freedesktop.org</a> <a href="http://lists.freedesktop.org/mailman/listinfo/mesa-dev" target="_blank">http://lists.freedesktop.org/mailman/listinfo/mesa-dev</a> </div></div></blockquote></div> </div></div>