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stage2: add lowering to I encoding

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Examples include push imm32.
This commit is contained in:
Jakub Konka 2021-12-23 10:01:03 +01:00
parent b657956c44
commit a70b4068c6
1 changed files with 56 additions and 34 deletions
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90
src/arch/x86_64/Emit.zig
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@ -215,16 +215,7 @@ fn mirPushPop(emit: *Emit, tag: Tag, inst: Mir.Inst.Index) InnerError!void {
// PUSH imm32
assert(tag == .push);
const imm = emit.mir.instructions.items(.data)[inst].imm;
const opc: u8 = if (imm <= math.maxInt(i8)) 0x6a else 0x6b;
const encoder = try Encoder.init(emit.code, 2);
encoder.opcode_1byte(opc);
if (imm <= math.maxInt(i8)) {
encoder.imm8(@intCast(i8, imm));
} else if (imm <= math.maxInt(i16)) {
encoder.imm16(@intCast(i16, imm));
} else {
encoder.imm32(imm);
}
return lowerToIEnc(.push, imm, emit.code);
},
0b11 => unreachable,
}
@ -422,31 +413,17 @@ fn mirTest(emit: *Emit, inst: Mir.Inst.Index) InnerError!void {
assert(tag == .@"test");
const ops = Mir.Ops.decode(emit.mir.instructions.items(.ops)[inst]);
switch (ops.flags) {
0b00 => blk: {
0b00 => {
if (ops.reg2 == .none) {
// TEST r/m64, imm32
// MI
const imm = emit.mir.instructions.items(.data)[inst].imm;
if (ops.reg1.to64() == .rax) {
// TODO reduce the size of the instruction if the immediate
// is smaller than 32 bits
const encoder = try Encoder.init(emit.code, 6);
encoder.rex(.{
.w = true,
});
encoder.opcode_1byte(0xa9);
encoder.imm32(imm);
break :blk;
// TEST rax, imm32
// I
return lowerToIEnc(.@"test", imm, emit.code);
}
const opc: u8 = if (ops.reg1.size() == 8) 0xf6 else 0xf7;
const encoder = try Encoder.init(emit.code, 7);
encoder.rex(.{
.w = true,
.b = ops.reg1.isExtended(),
});
encoder.opcode_1byte(opc);
encoder.modRm_direct(0, ops.reg1.lowId());
encoder.imm8(@intCast(i8, imm));
break :blk;
return lowerToMiEnc(.@"test", RegisterOrMemory.reg(ops.reg1), imm, emit.code);
}
// TEST r/m64, r64
return emit.fail("TODO TEST r/m64, r64", .{});
@ -463,16 +440,16 @@ fn mirRet(emit: *Emit, inst: Mir.Inst.Index) InnerError!void {
switch (ops.flags) {
0b00 => {
// RETF imm16
// I
const imm = emit.mir.instructions.items(.data)[inst].imm;
encoder.opcode_1byte(0xca);
encoder.imm16(@intCast(i16, imm));
return lowerToIEnc(.ret_far, imm, emit.code);
},
0b01 => encoder.opcode_1byte(0xcb), // RETF
0b10 => {
// RET imm16
// I
const imm = emit.mir.instructions.items(.data)[inst].imm;
encoder.opcode_1byte(0xc2);
encoder.imm16(@intCast(i16, imm));
return lowerToIEnc(.ret_near, imm, emit.code);
},
0b11 => encoder.opcode_1byte(0xc3), // RET
}
@ -493,6 +470,9 @@ const Tag = enum {
call_near,
push,
pop,
@"test",
ret_near,
ret_far,
};
const Encoding = enum {
@ -505,6 +485,9 @@ const Encoding = enum {
/// OP r64
o,
/// OP imm32
i,
/// OP r/m64, imm32
mi,
@ -541,9 +524,17 @@ inline fn getOpCode(tag: Tag, enc: Encoding) ?u8 {
.pop => 0x58,
else => null,
},
.i => return switch (tag) {
.push => 0x68,
.@"test" => 0xa9,
.ret_near => 0xc2,
.ret_far => 0xca,
else => null,
},
.mi => return switch (tag) {
.adc, .add, .sub, .xor, .@"and", .@"or", .sbb, .cmp => 0x81,
.mov => 0xc7,
.@"test" => 0xf7,
else => null,
},
.mr => return switch (tag) {
@ -601,6 +592,7 @@ inline fn getModRmExt(tag: Tag) ?u3 {
.call_near => 0x2,
.push => 0x6,
.pop => 0x0,
.@"test" => 0x0,
else => null,
};
}
@ -646,6 +638,36 @@ const RegisterOrMemory = union(enum) {
}
};
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) {
const encoder = try Encoder.init(code, 3);
encoder.opcode_1byte(opc);
encoder.imm16(@intCast(i16, imm));
return;
}
if (immOpSize(imm) == 8) {
// TODO I think getOpCode should track this
switch (tag) {
.push => opc += 2,
.@"test" => opc -= 1,
else => return error.EmitFail,
}
}
const encoder = try Encoder.init(code, 5);
if (immOpSize(imm) == 16) {
encoder.opcode_1byte(0x66);
}
encoder.opcode_1byte(opc);
if (immOpSize(imm) == 8) {
encoder.imm8(@intCast(i8, imm));
} else if (immOpSize(imm) == 16) {
encoder.imm16(@intCast(i16, imm));
} else {
encoder.imm32(imm);
}
}
fn lowerToOEnc(tag: Tag, reg: Register, code: *std.ArrayList(u8)) InnerError!void {
if (reg.size() != 16 and reg.size() != 64) return error.EmitFail; // TODO correct for push/pop, but is it universal?
const opc = getOpCode(tag, .o).?;