authorgravatar for kubkon@jakubkonka.comJakub Konka <kubkon@jakubkonka.com> 2021-12-23 17:51:19+01:00
committergravatar for kubkon@jakubkonka.comJakub Konka <kubkon@jakubkonka.com> 2021-12-23 18:49:40+01:00
logd23a1487bd397ce86108ae2727b67a1d0614f7a9
treec0c87facf901c419f6f2aa08d0eeff98c18574e4
parenta70b4068c6a8585da8b0a28326010807e5c427c1

stage2: add lowering of ZO encoding

ZO (probably) stands for zero operands encoding which is effectively only the opcode.

1 files changed, 22 insertions(+), 7 deletions(-)

src/arch/x86_64/Emit.zig+22-7
......@@ -185,13 +185,11 @@ fn fixupRelocs(emit: *Emit) InnerError!void {
185185}
186186
187187fn mirBrk(emit: *Emit) InnerError!void {
188 const encoder = try Encoder.init(emit.code, 1);
189 encoder.opcode_1byte(0xcc);
188 return lowerToZoEnc(.brk, emit.code);
190189}
191190
192191fn mirNop(emit: *Emit) InnerError!void {
193 const encoder = try Encoder.init(emit.code, 1);
194 encoder.opcode_1byte(0x90);
192 return lowerToZoEnc(.nop, emit.code);
195193}
196194
197195fn mirSyscall(emit: *Emit) InnerError!void {
......@@ -436,7 +434,6 @@ fn mirRet(emit: *Emit, inst: Mir.Inst.Index) InnerError!void {
436434 const tag = emit.mir.instructions.items(.tag)[inst];
437435 assert(tag == .ret);
438436 const ops = Mir.Ops.decode(emit.mir.instructions.items(.ops)[inst]);
439 const encoder = try Encoder.init(emit.code, 3);
440437 switch (ops.flags) {
441438 0b00 => {
442439 // RETF imm16
......@@ -444,14 +441,14 @@ fn mirRet(emit: *Emit, inst: Mir.Inst.Index) InnerError!void {
444441 const imm = emit.mir.instructions.items(.data)[inst].imm;
445442 return lowerToIEnc(.ret_far, imm, emit.code);
446443 },
447 0b01 => encoder.opcode_1byte(0xcb), // RETF
444 0b01 => return lowerToZoEnc(.ret_far, emit.code),
448445 0b10 => {
449446 // RET imm16
450447 // I
451448 const imm = emit.mir.instructions.items(.data)[inst].imm;
452449 return lowerToIEnc(.ret_near, imm, emit.code);
453450 },
454 0b11 => encoder.opcode_1byte(0xc3), // RET
451 0b11 => return lowerToZoEnc(.ret_near, emit.code),
455452 }
456453}
457454
......@@ -471,11 +468,16 @@ const Tag = enum {
471468 push,
472469 pop,
473470 @"test",
471 brk,
472 nop,
474473 ret_near,
475474 ret_far,
476475};
477476
478477const Encoding = enum {
478 /// OP
479 zo,
480
479481 /// OP rel32
480482 d,
481483
......@@ -509,6 +511,13 @@ const Encoding = enum {
509511
510512inline fn getOpCode(tag: Tag, enc: Encoding) ?u8 {
511513 switch (enc) {
514 .zo => return switch (tag) {
515 .ret_near => 0xc3,
516 .ret_far => 0xcb,
517 .brk => 0xcc,
518 .nop => 0x90,
519 else => null,
520 },
512521 .d => return switch (tag) {
513522 .jmp_near => 0xe9,
514523 .call_near => 0xe8,
......@@ -638,6 +647,12 @@ const RegisterOrMemory = union(enum) {
638647 }
639648};
640649
650fn lowerToZoEnc(tag: Tag, code: *std.ArrayList(u8)) InnerError!void {
651 const opc = getOpCode(tag, .zo).?;
652 const encoder = try Encoder.init(code, 1);
653 encoder.opcode_1byte(opc);
654}
655
641656fn lowerToIEnc(tag: Tag, imm: i32, code: *std.ArrayList(u8)) InnerError!void {
642657 var opc = getOpCode(tag, .i).?;
643658 if (tag == .ret_far or tag == .ret_near) {