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stage2: codegen: fix off-by-one stack variable offsets

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This commit is contained in:
Andrew Kelley 2020-07-29 02:28:35 -07:00
parent 606f157a6b
commit 8899e6e334
1 changed files with 14 additions and 8 deletions
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22
src-self-hosted/codegen.zig
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@ -1346,11 +1346,13 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
return self.fail(src, "TODO implement set stack variable with compare flags value (signed)", .{});
},
.immediate => |x_big| {
if (stack_offset > 128) {
const abi_size = ty.abiSize(self.target.*);
const adj_off = stack_offset + abi_size;
if (adj_off > 128) {
return self.fail(src, "TODO implement set stack variable with large stack offset", .{});
}
try self.code.ensureCapacity(self.code.items.len + 8);
switch (ty.abiSize(self.target.*)) {
switch (abi_size) {
1 => {
return self.fail(src, "TODO implement set abi_size=1 stack variable with immediate", .{});
},
@ -1361,7 +1363,7 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
const x = @intCast(u32, x_big);
// We have a positive stack offset value but we want a twos complement negative
// offset from rbp, which is at the top of the stack frame.
const negative_offset = @intCast(i8, -@intCast(i32, stack_offset));
const negative_offset = @intCast(i8, -@intCast(i32, adj_off));
const twos_comp = @bitCast(u8, negative_offset);
// mov DWORD PTR [rbp+offset], immediate
self.code.appendSliceAssumeCapacity(&[_]u8{ 0xc7, 0x45, twos_comp });
@ -1382,19 +1384,21 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
return self.fail(src, "TODO implement set stack variable from embedded_in_code", .{});
},
.register => |reg| {
const abi_size = ty.abiSize(self.target.*);
const adj_off = stack_offset + abi_size;
try self.code.ensureCapacity(self.code.items.len + 7);
self.rex(.{ .w = reg.size() == 64, .b = reg.isExtended() });
const reg_id: u8 = @truncate(u3, reg.id());
if (stack_offset <= 128) {
if (adj_off <= 128) {
// example: 48 89 55 7f mov QWORD PTR [rbp+0x7f],rdx
const RM = @as(u8, 0b01_000_101) | (reg_id << 3);
const negative_offset = @intCast(i8, -@intCast(i32, stack_offset));
const negative_offset = @intCast(i8, -@intCast(i32, adj_off));
const twos_comp = @bitCast(u8, negative_offset);
self.code.appendSliceAssumeCapacity(&[_]u8{ 0x89, RM, twos_comp });
} else if (stack_offset <= 2147483648) {
} else if (adj_off <= 2147483648) {
// example: 48 89 95 80 00 00 00 mov QWORD PTR [rbp+0x80],rdx
const RM = @as(u8, 0b10_000_101) | (reg_id << 3);
const negative_offset = @intCast(i32, -@intCast(i33, stack_offset));
const negative_offset = @intCast(i32, -@intCast(i33, adj_off));
const twos_comp = @bitCast(u32, negative_offset);
self.code.appendSliceAssumeCapacity(&[_]u8{ 0x89, RM });
mem.writeIntLittle(u32, self.code.addManyAsArrayAssumeCapacity(4), twos_comp);
@ -1605,8 +1609,10 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
}
}
},
.stack_offset => |off| {
.stack_offset => |unadjusted_off| {
try self.code.ensureCapacity(self.code.items.len + 7);
const size_bytes = @divExact(reg.size(), 8);
const off = unadjusted_off + size_bytes;
self.rex(.{ .w = reg.size() == 64, .r = reg.isExtended() });
const reg_id: u8 = @truncate(u3, reg.id());
if (off <= 128) {