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detect comptime var references in asm input/output and improve errors

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xdBronch 2025-10-15 00:33:12 -04:00
parent 493ad58ff7
commit 717ac0d5ce
6 changed files with 87 additions and 35 deletions
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2
lib/std/zig/AstGen.zig
View file

@ -12906,9 +12906,9 @@ const GenZir = struct {
}
const small: Zir.Inst.Asm.Small = .{
.is_volatile = args.is_volatile,
.outputs_len = @intCast(args.outputs.len),
.inputs_len = @intCast(args.inputs.len),
.is_volatile = args.is_volatile,
};
const new_index: Zir.Inst.Index = @enumFromInt(astgen.instructions.len);

29
src/Sema.zig
View file

@ -16303,6 +16303,7 @@ fn zirAsm(
const pt = sema.pt;
const zcu = pt.zcu;
const ip = &zcu.intern_pool;
const extra = sema.code.extraData(Zir.Inst.Asm, extended.operand);
const src = block.nodeOffset(extra.data.src_node);
const ret_ty_src = block.src(.{ .node_offset_asm_ret_ty = extra.data.src_node });
@ -16348,28 +16349,38 @@ fn zirAsm(
for (out_args, 0..) |*arg, out_i| {
const output = sema.code.extraData(Zir.Inst.Asm.Output, extra_i);
const output_src = block.src(.{ .asm_output = .{
.offset = src.offset.node_offset.x,
.output_index = @intCast(out_i),
} });
extra_i = output.end;
const is_type = @as(u1, @truncate(output_type_bits)) != 0;
output_type_bits >>= 1;
const name = sema.code.nullTerminatedString(output.data.name);
if (is_type) {
// Indicate the output is the asm instruction return value.
arg.* = .none;
const out_ty = try sema.resolveType(block, ret_ty_src, output.data.operand);
expr_ty = Air.internedToRef(out_ty.toIntern());
} else {
arg.* = try sema.resolveInst(output.data.operand);
const inst = try sema.resolveInst(output.data.operand);
if (!sema.checkRuntimeValue(inst)) {
const output_name = try ip.getOrPutString(sema.gpa, pt.tid, name, .no_embedded_nulls);
return sema.failWithContainsReferenceToComptimeVar(block, output_src, output_name, "assembly output", .fromInterned(inst.toInterned().?));
}
arg.* = inst;
}
const constraint = sema.code.nullTerminatedString(output.data.constraint);
const name = sema.code.nullTerminatedString(output.data.name);
needed_capacity += (constraint.len + name.len + (2 + 3)) / 4;
if (output.data.operand.toIndex()) |index| {
if (zir_tags[@intFromEnum(index)] == .ref) {
// TODO: better error location; it would be even nicer if there were notes that pointed at the output and the variable definition
return sema.fail(block, src, "asm cannot output to const local '{s}'", .{name});
// TODO: it would be even nicer if there were notes that pointed at the variable definition
return sema.fail(block, output_src, "asm cannot output to const local '{s}'", .{name});
}
}
@ -16381,9 +16392,18 @@ fn zirAsm(
for (args, 0..) |*arg, arg_i| {
const input = sema.code.extraData(Zir.Inst.Asm.Input, extra_i);
const input_src = block.src(.{ .asm_input = .{
.offset = src.offset.node_offset.x,
.input_index = @intCast(arg_i),
} });
extra_i = input.end;
const uncasted_arg = try sema.resolveInst(input.data.operand);
const name = sema.code.nullTerminatedString(input.data.name);
if (!sema.checkRuntimeValue(uncasted_arg)) {
const input_name = try ip.getOrPutString(sema.gpa, pt.tid, name, .no_embedded_nulls);
return sema.failWithContainsReferenceToComptimeVar(block, input_src, input_name, "assembly input", .fromInterned(uncasted_arg.toInterned().?));
}
const uncasted_arg_ty = sema.typeOf(uncasted_arg);
switch (uncasted_arg_ty.zigTypeTag(zcu)) {
.comptime_int => arg.* = try sema.coerce(block, .usize, uncasted_arg, src),
@ -16394,7 +16414,6 @@ fn zirAsm(
}
const constraint = sema.code.nullTerminatedString(input.data.constraint);
const name = sema.code.nullTerminatedString(input.data.name);
needed_capacity += (constraint.len + name.len + (2 + 3)) / 4;
inputs[arg_i] = .{ .c = constraint, .n = name };
}

31
src/Zcu.zig
View file

@ -1516,6 +1516,25 @@ pub const SrcLoc = struct {
};
return tree.nodeToSpan(src_node);
},
.asm_input => |input| {
const tree = try src_loc.file_scope.getTree(zcu);
const node = input.offset.toAbsolute(src_loc.base_node);
const full = tree.fullAsm(node).?;
const asm_input = full.inputs[input.input_index];
return tree.nodeToSpan(tree.nodeData(asm_input).node_and_token[0]);
},
.asm_output => |output| {
const tree = try src_loc.file_scope.getTree(zcu);
const node = output.offset.toAbsolute(src_loc.base_node);
const full = tree.fullAsm(node).?;
const asm_output = full.outputs[output.output_index];
const data = tree.nodeData(asm_output).opt_node_and_token;
return if (data[0].unwrap()) |output_node|
tree.nodeToSpan(output_node)
else
// token points to the ')'
tree.tokenToSpan(data[1] - 1);
},
.for_input => |for_input| {
const tree = try src_loc.file_scope.getTree(zcu);
const node = for_input.for_node_offset.toAbsolute(src_loc.base_node);
@ -2481,6 +2500,18 @@ pub const LazySrcLoc = struct {
/// The source location points to the operand of a `return` statement, or
/// the `return` itself if there is no explicit operand.
node_offset_return_operand: Ast.Node.Offset,
/// The source location points to an assembly input
asm_input: struct {
/// Points to the assembly node
offset: Ast.Node.Offset,
input_index: u32,
},
/// The source location points to an assembly output
asm_output: struct {
/// Points to the assembly node
offset: Ast.Node.Offset,
output_index: u32,
},
/// The source location points to a for loop input.
for_input: struct {
/// Points to the for loop AST node.

37
src/print_zir.zig
View file

@ -1185,18 +1185,14 @@ const Writer = struct {
tmpl_is_expr: bool,
) !void {
const extra = self.code.extraData(Zir.Inst.Asm, extended.operand);
const outputs_len = @as(u5, @truncate(extended.small));
const inputs_len = @as(u5, @truncate(extended.small >> 5));
const clobbers_len = @as(u5, @truncate(extended.small >> 10));
const is_volatile = @as(u1, @truncate(extended.small >> 15)) != 0;
const small: Zir.Inst.Asm.Small = @bitCast(extended.small);
try self.writeFlag(stream, "volatile, ", is_volatile);
try self.writeFlag(stream, "volatile, ", small.is_volatile);
if (tmpl_is_expr) {
try self.writeInstRef(stream, @enumFromInt(@intFromEnum(extra.data.asm_source)));
try stream.writeAll(", ");
} else {
const asm_source = self.code.nullTerminatedString(extra.data.asm_source);
try stream.print("\"{f}\", ", .{std.zig.fmtString(asm_source)});
try stream.print("\"{f}\"", .{std.zig.fmtString(asm_source)});
}
try stream.writeAll(", ");
@ -1204,7 +1200,7 @@ const Writer = struct {
var output_type_bits = extra.data.output_type_bits;
{
var i: usize = 0;
while (i < outputs_len) : (i += 1) {
while (i < small.outputs_len) : (i += 1) {
const output = self.code.extraData(Zir.Inst.Asm.Output, extra_i);
extra_i = output.end;
@ -1216,17 +1212,14 @@ const Writer = struct {
try stream.print("output({f}, \"{f}\", ", .{
std.zig.fmtIdP(name), std.zig.fmtString(constraint),
});
try self.writeFlag(stream, "->", is_type);
try self.writeFlag(stream, "-> ", is_type);
try self.writeInstRef(stream, output.data.operand);
try stream.writeAll(")");
if (i + 1 < outputs_len) {
try stream.writeAll("), ");
}
try stream.writeAll("), ");
}
}
{
var i: usize = 0;
while (i < inputs_len) : (i += 1) {
while (i < small.inputs_len) : (i += 1) {
const input = self.code.extraData(Zir.Inst.Asm.Input, extra_i);
extra_i = input.end;
@ -1236,23 +1229,11 @@ const Writer = struct {
std.zig.fmtIdP(name), std.zig.fmtString(constraint),
});
try self.writeInstRef(stream, input.data.operand);
try stream.writeAll(")");
if (i + 1 < inputs_len) {
try stream.writeAll(", ");
}
try stream.writeAll("), ");
}
}
{
var i: usize = 0;
while (i < clobbers_len) : (i += 1) {
const str_index = self.code.extra[extra_i];
extra_i += 1;
const clobber = self.code.nullTerminatedString(@enumFromInt(str_index));
try stream.print("{f}", .{std.zig.fmtIdP(clobber)});
if (i + 1 < clobbers_len) {
try stream.writeAll(", ");
}
}
try self.writeInstRef(stream, extra.data.clobbers);
}
try stream.writeAll(")) ");
try self.writeSrcNode(stream, extra.data.src_node);

2
test/cases/compile_errors/asm_output_to_const.zig
View file

@ -9,4 +9,4 @@ export fn foo() void {
// error
//
// :4:5: error: asm cannot output to const local 'f'
// :6:21: error: asm cannot output to const local 'f'

21
test/cases/compile_errors/comptime_var_referenced_by_asm.zig Normal file
View file

@ -0,0 +1,21 @@
export fn foo() void {
comptime var a: u32 = 0;
_ = asm volatile (""
:
: [in] "r" (&a),
);
}
export fn bar() void {
comptime var a: u32 = 0;
_ = asm volatile (""
: [out] "=r" (a),
);
}
// error
//
// :5:21: error: assembly input contains reference to comptime var
// :2:14: note: 'in' points to comptime var declared here
// :12:23: error: assembly output contains reference to comptime var
// :10:14: note: 'out' points to comptime var declared here