Commit 71c5eebd32d44ca01fedcb48674c5e7185f10289 | zig

author	Jakub Konka <kubkon@jakubkonka.com> 2021-12-20 18:20:06+01:00
committer	Jakub Konka <kubkon@jakubkonka.com> 2021-12-20 18:20:06+01:00
log	71c5eebd32d44ca01fedcb48674c5e7185f10289
tree	2f58bd79d159f7c8952af53fe68e78e17e312003
parent	4a40c0a80c8f7014097f3ac6f523c7e21cda80a9

stage2: remove obsolete MOV variant 0b11

* variant `0b11` when both `reg1 != .none` and `reg2 != .none` is
  identical to `0b00` therefore it can safely be removed
* fix proper destination register size calculation when setting register from
  another source register

3 files changed, 3 insertions(+), 14 deletions(-)

src
- arch
  - x86_64
    CodeGen.zig
    Emit.zig
    Mir.zig

src/arch/x86_64/CodeGen.zig+1-2

...	...	@@ -2968,9 +2968,8 @@ fn genSetReg(self: *Self, ty: Type, reg: Register, mcv: MCValue) InnerError!void
2968	2968	_ = try self.addInst(.{
2969	2969	.tag = .mov,
2970	2970	.ops = (Mir.Ops{
2971		.reg1 = reg,
	2971	.reg1 = registerAlias(reg, @divExact(src_reg.size(), 8)),
2972	2972	.reg2 = src_reg,
2973		.flags = 0b11,
2974	2973	}).encode(),
2975	2974	.data = undefined,
2976	2975	});

src/arch/x86_64/Emit.zig+1-11

...	...	@@ -1119,17 +1119,7 @@ fn mirMovImpl(
1119	1119	encoder.imm32(imm_op);
1120	1120	break :blk;
1121	1121	}
1122		// mov reg1, reg2
1123		// RM
1124		const opc: u8 = if (ops.reg1.size() == 8) 0x8a else 0x8b;
1125		const encoder = try Encoder.init(code, 3);
1126		encoder.rex(.{
1127		.w = ops.reg1.size() == 64 and ops.reg2.size() == 64,
1128		.r = ops.reg1.isExtended(),
1129		.b = ops.reg2.isExtended(),
1130		});
1131		encoder.opcode_1byte(opc);
1132		encoder.modRm_direct(ops.reg1.lowId(), ops.reg2.lowId());
	1122	return EmitResult.err(allocator, src_loc, "TODO unused variant: mov reg1, reg2, 0b11", .{});
1133	1123	},
1134	1124	}
1135	1125	return EmitResult.ok();

src/arch/x86_64/Mir.zig+1-1

...	...	@@ -145,7 +145,7 @@ pub const Inst = struct {
145	145	/// 0b10 [reg1 + imm32], reg2
146	146	/// 0b10 [reg1 + 0], imm32
147	147	/// 0b11 [reg1 + imm32], imm32
148		/// 0b11 reg1, reg2 (RM)
	148	/// 0b11 AVAILABLE
149	149	/// Notes:
150	150	/// * If reg2 is `none` then it means Data field `imm` is used as the immediate.
151	151	/// * When two imm32 values are required, Data field `payload` points at `ImmPair`.