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stage2: add lowering of ZO encoding

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ZO (probably) stands for zero operands encoding which is effectively
only the opcode.
This commit is contained in:
Jakub Konka 2021-12-23 17:51:19 +01:00
parent a70b4068c6
commit d23a1487bd
1 changed files with 22 additions and 7 deletions
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29
src/arch/x86_64/Emit.zig
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@ -185,13 +185,11 @@ fn fixupRelocs(emit: *Emit) InnerError!void {
}
fn mirBrk(emit: *Emit) InnerError!void {
const encoder = try Encoder.init(emit.code, 1);
encoder.opcode_1byte(0xcc);
return lowerToZoEnc(.brk, emit.code);
}
fn mirNop(emit: *Emit) InnerError!void {
const encoder = try Encoder.init(emit.code, 1);
encoder.opcode_1byte(0x90);
return lowerToZoEnc(.nop, emit.code);
}
fn mirSyscall(emit: *Emit) InnerError!void {
@ -436,7 +434,6 @@ fn mirRet(emit: *Emit, inst: Mir.Inst.Index) InnerError!void {
const tag = emit.mir.instructions.items(.tag)[inst];
assert(tag == .ret);
const ops = Mir.Ops.decode(emit.mir.instructions.items(.ops)[inst]);
const encoder = try Encoder.init(emit.code, 3);
switch (ops.flags) {
0b00 => {
// RETF imm16
@ -444,14 +441,14 @@ fn mirRet(emit: *Emit, inst: Mir.Inst.Index) InnerError!void {
const imm = emit.mir.instructions.items(.data)[inst].imm;
return lowerToIEnc(.ret_far, imm, emit.code);
},
0b01 => encoder.opcode_1byte(0xcb), // RETF
0b01 => return lowerToZoEnc(.ret_far, emit.code),
0b10 => {
// RET imm16
// I
const imm = emit.mir.instructions.items(.data)[inst].imm;
return lowerToIEnc(.ret_near, imm, emit.code);
},
0b11 => encoder.opcode_1byte(0xc3), // RET
0b11 => return lowerToZoEnc(.ret_near, emit.code),
}
}
@ -471,11 +468,16 @@ const Tag = enum {
push,
pop,
@"test",
brk,
nop,
ret_near,
ret_far,
};
const Encoding = enum {
/// OP
zo,
/// OP rel32
d,
@ -509,6 +511,13 @@ const Encoding = enum {
inline fn getOpCode(tag: Tag, enc: Encoding) ?u8 {
switch (enc) {
.zo => return switch (tag) {
.ret_near => 0xc3,
.ret_far => 0xcb,
.brk => 0xcc,
.nop => 0x90,
else => null,
},
.d => return switch (tag) {
.jmp_near => 0xe9,
.call_near => 0xe8,
@ -638,6 +647,12 @@ const RegisterOrMemory = union(enum) {
}
};
fn lowerToZoEnc(tag: Tag, code: *std.ArrayList(u8)) InnerError!void {
const opc = getOpCode(tag, .zo).?;
const encoder = try Encoder.init(code, 1);
encoder.opcode_1byte(opc);
}
fn lowerToIEnc(tag: Tag, imm: i32, code: *std.ArrayList(u8)) InnerError!void {
var opc = getOpCode(tag, .i).?;
if (tag == .ret_far or tag == .ret_near) {