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stage2: optional comparison and 0-bit payloads

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* Sema: implement peer type resolution for optionals and null.
 * Rename `Module.optionalType` to `Type.optional`.
 * LLVM backend: re-use anonymous values. This is especially useful when
   isByRef()=true because it means re-using the same generated LLVM globals.
 * LLVM backend: rework the implementation of is_null and is_non_null
   AIR instructions. Generate slightly better LLVM code, and also fix
   the behavior for optionals whose payload type is 0-bit.
 * LLVM backend: improve `cmp` AIR instruction lowering to support
   pointer-like optionals.
 * `Value`: implement support for equality-checking optionals.
This commit is contained in:
Andrew Kelley
2021-10-15 18:37:09 -07:00
parent 186126c2a4
commit 682cdeceaa
7 changed files with 171 additions and 96 deletions
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14
src/Module.zig
View File

@@ -4249,20 +4249,6 @@ pub fn errNoteNonLazy(
};
}
pub fn optionalType(arena: *Allocator, child_type: Type) Allocator.Error!Type {
switch (child_type.tag()) {
.single_const_pointer => return Type.Tag.optional_single_const_pointer.create(
arena,
child_type.elemType(),
),
.single_mut_pointer => return Type.Tag.optional_single_mut_pointer.create(
arena,
child_type.elemType(),
),
else => return Type.Tag.optional.create(arena, child_type),
}
}
pub fn errorUnionType(
arena: *Allocator,
error_set: Type,

56
src/Sema.zig
View File

@@ -4108,7 +4108,7 @@ fn zirOptionalType(sema: *Sema, block: *Block, inst: Zir.Inst.Index) CompileErro
const inst_data = sema.code.instructions.items(.data)[inst].un_node;
const src = inst_data.src();
const child_type = try sema.resolveType(block, src, inst_data.operand);
const opt_type = try Module.optionalType(sema.arena, child_type);
const opt_type = try Type.optional(sema.arena, child_type);
return sema.addType(opt_type);
}
@@ -9675,7 +9675,7 @@ fn zirCmpxchg(
return sema.fail(block, failure_order_src, "failure atomic ordering must not be Release or AcqRel", .{});
}
const result_ty = try Module.optionalType(sema.arena, elem_ty);
const result_ty = try Type.optional(sema.arena, elem_ty);
// special case zero bit types
if ((try sema.typeHasOnePossibleValue(block, elem_ty_src, elem_ty)) != null) {
@@ -10517,7 +10517,7 @@ fn panicWithMsg(
.@"addrspace" = target_util.defaultAddressSpace(mod.getTarget(), .global_constant), // TODO might need a place that is more dynamic
});
const null_stack_trace = try sema.addConstant(
try Module.optionalType(arena, ptr_stack_trace_ty),
try Type.optional(arena, ptr_stack_trace_ty),
Value.initTag(.null_value),
);
const args = try arena.create([2]Air.Inst.Ref);
@@ -12797,6 +12797,7 @@ fn resolvePeerTypes(
const target = sema.mod.getTarget();
var chosen = instructions[0];
var any_are_null = false;
var chosen_i: usize = 0;
for (instructions[1..]) |candidate, candidate_i| {
const candidate_ty = sema.typeOf(candidate);
@@ -12878,6 +12879,44 @@ fn resolvePeerTypes(
continue;
}
if (chosen_ty_tag == .Null) {
any_are_null = true;
chosen = candidate;
chosen_i = candidate_i + 1;
continue;
}
if (candidate_ty_tag == .Null) {
any_are_null = true;
continue;
}
if (chosen_ty_tag == .Optional) {
var opt_child_buf: Type.Payload.ElemType = undefined;
const opt_child_ty = chosen_ty.optionalChild(&opt_child_buf);
if (coerceInMemoryAllowed(opt_child_ty, candidate_ty, false, target) == .ok) {
continue;
}
if (coerceInMemoryAllowed(candidate_ty, opt_child_ty, false, target) == .ok) {
any_are_null = true;
chosen = candidate;
chosen_i = candidate_i + 1;
continue;
}
}
if (candidate_ty_tag == .Optional) {
var opt_child_buf: Type.Payload.ElemType = undefined;
const opt_child_ty = candidate_ty.optionalChild(&opt_child_buf);
if (coerceInMemoryAllowed(opt_child_ty, chosen_ty, false, target) == .ok) {
chosen = candidate;
chosen_i = candidate_i + 1;
continue;
}
if (coerceInMemoryAllowed(chosen_ty, opt_child_ty, false, target) == .ok) {
any_are_null = true;
continue;
}
}
// At this point, we hit a compile error. We need to recover
// the source locations.
const chosen_src = candidate_srcs.resolve(
@@ -12906,7 +12945,16 @@ fn resolvePeerTypes(
return sema.failWithOwnedErrorMsg(msg);
}
return sema.typeOf(chosen);
const chosen_ty = sema.typeOf(chosen);
if (any_are_null) {
switch (chosen_ty.zigTypeTag()) {
.Null, .Optional => return chosen_ty,
else => return Type.optional(sema.arena, chosen_ty),
}
}
return chosen_ty;
}
pub fn resolveTypeLayout(

117
src/codegen/llvm.zig
View File

@@ -1430,7 +1430,7 @@ pub const FuncGen = struct {
/// This stores the LLVM values used in a function, such that they can be referred to
/// in other instructions. This table is cleared before every function is generated.
func_inst_table: std.AutoHashMapUnmanaged(Air.Inst.Index, *const llvm.Value),
func_inst_table: std.AutoHashMapUnmanaged(Air.Inst.Ref, *const llvm.Value),
/// If the return type isByRef, this is the result pointer. Otherwise null.
ret_ptr: ?*const llvm.Value,
@@ -1472,23 +1472,27 @@ pub const FuncGen = struct {
}
fn resolveInst(self: *FuncGen, inst: Air.Inst.Ref) !*const llvm.Value {
if (self.air.value(inst)) |val| {
const ty = self.air.typeOf(inst);
const llvm_val = try self.dg.genTypedValue(.{ .ty = ty, .val = val });
if (!isByRef(ty)) return llvm_val;
const gop = try self.func_inst_table.getOrPut(self.dg.gpa, inst);
if (gop.found_existing) return gop.value_ptr.*;
// We have an LLVM value but we need to create a global constant and
// set the value as its initializer, and then return a pointer to the global.
const target = self.dg.module.getTarget();
const global = self.dg.object.llvm_module.addGlobal(llvm_val.typeOf(), "");
global.setInitializer(llvm_val);
global.setLinkage(.Private);
global.setGlobalConstant(.True);
global.setAlignment(ty.abiAlignment(target));
return global;
const val = self.air.value(inst).?;
const ty = self.air.typeOf(inst);
const llvm_val = try self.dg.genTypedValue(.{ .ty = ty, .val = val });
if (!isByRef(ty)) {
gop.value_ptr.* = llvm_val;
return llvm_val;
}
const inst_index = Air.refToIndex(inst).?;
return self.func_inst_table.get(inst_index).?;
// We have an LLVM value but we need to create a global constant and
// set the value as its initializer, and then return a pointer to the global.
const target = self.dg.module.getTarget();
const global = self.dg.object.llvm_module.addGlobal(llvm_val.typeOf(), "");
global.setInitializer(llvm_val);
global.setLinkage(.Private);
global.setGlobalConstant(.True);
global.setAlignment(ty.abiAlignment(target));
gop.value_ptr.* = global;
return global;
}
fn genBody(self: *FuncGen, body: []const Air.Inst.Index) Error!void {
@@ -1528,10 +1532,11 @@ pub const FuncGen = struct {
.cmp_lte => try self.airCmp(inst, .lte),
.cmp_neq => try self.airCmp(inst, .neq),
.is_non_null => try self.airIsNonNull(inst, false),
.is_non_null_ptr => try self.airIsNonNull(inst, true),
.is_null => try self.airIsNull(inst, false),
.is_null_ptr => try self.airIsNull(inst, true),
.is_non_null => try self.airIsNonNull(inst, false, false, .NE),
.is_non_null_ptr => try self.airIsNonNull(inst, true , false, .NE),
.is_null => try self.airIsNonNull(inst, false, true , .EQ),
.is_null_ptr => try self.airIsNonNull(inst, true , true , .EQ),
.is_non_err => try self.airIsErr(inst, .EQ, false),
.is_non_err_ptr => try self.airIsErr(inst, .EQ, true),
.is_err => try self.airIsErr(inst, .NE, false),
@@ -1618,7 +1623,10 @@ pub const FuncGen = struct {
},
// zig fmt: on
};
if (opt_value) |val| try self.func_inst_table.putNoClobber(self.gpa, inst, val);
if (opt_value) |val| {
const ref = Air.indexToRef(inst);
try self.func_inst_table.putNoClobber(self.gpa, ref, val);
}
}
}
@@ -1722,8 +1730,7 @@ pub const FuncGen = struct {
}
fn airCmp(self: *FuncGen, inst: Air.Inst.Index, op: math.CompareOperator) !?*const llvm.Value {
if (self.liveness.isUnused(inst))
return null;
if (self.liveness.isUnused(inst)) return null;
const bin_op = self.air.instructions.items(.data)[inst].bin_op;
const lhs = try self.resolveInst(bin_op.lhs);
@@ -1733,7 +1740,7 @@ pub const FuncGen = struct {
const int_ty = switch (operand_ty.zigTypeTag()) {
.Enum => operand_ty.intTagType(&buffer),
.Int, .Bool, .Pointer, .ErrorSet => operand_ty,
.Int, .Bool, .Pointer, .Optional, .ErrorSet => operand_ty,
.Float => {
const operation: llvm.RealPredicate = switch (op) {
.eq => .OEQ,
@@ -2227,45 +2234,57 @@ pub const FuncGen = struct {
);
}
fn airIsNonNull(self: *FuncGen, inst: Air.Inst.Index, operand_is_ptr: bool) !?*const llvm.Value {
if (self.liveness.isUnused(inst))
return null;
fn airIsNonNull(
self: *FuncGen,
inst: Air.Inst.Index,
operand_is_ptr: bool,
invert: bool,
pred: llvm.IntPredicate,
) !?*const llvm.Value {
if (self.liveness.isUnused(inst)) return null;
const un_op = self.air.instructions.items(.data)[inst].un_op;
const operand = try self.resolveInst(un_op);
if (operand_is_ptr) {
const operand_ty = self.air.typeOf(un_op).elemType();
if (operand_ty.isPtrLikeOptional()) {
const operand_llvm_ty = try self.dg.llvmType(operand_ty);
const loaded = self.builder.buildLoad(operand, "");
return self.builder.buildICmp(.NE, loaded, operand_llvm_ty.constNull(), "");
const operand_ty = self.air.typeOf(un_op);
const optional_ty = if (operand_is_ptr) operand_ty.childType() else operand_ty;
var buf: Type.Payload.ElemType = undefined;
const payload_ty = optional_ty.optionalChild(&buf);
if (!payload_ty.hasCodeGenBits()) {
if (invert) {
return self.builder.buildNot(operand, "");
} else {
return operand;
}
}
if (optional_ty.isPtrLikeOptional()) {
const optional_llvm_ty = try self.dg.llvmType(optional_ty);
const loaded = if (operand_is_ptr) self.builder.buildLoad(operand, "") else operand;
return self.builder.buildICmp(pred, loaded, optional_llvm_ty.constNull(), "");
}
if (operand_is_ptr or isByRef(optional_ty)) {
const index_type = self.context.intType(32);
var indices: [2]*const llvm.Value = .{
const indices: [2]*const llvm.Value = .{
index_type.constNull(),
index_type.constInt(1, .False),
};
return self.builder.buildLoad(self.builder.buildInBoundsGEP(operand, &indices, indices.len, ""), "");
const field_ptr = self.builder.buildInBoundsGEP(operand, &indices, indices.len, "");
const non_null_bit = self.builder.buildLoad(field_ptr, "");
if (invert) {
return self.builder.buildNot(non_null_bit, "");
} else {
return non_null_bit;
}
}
const operand_ty = self.air.typeOf(un_op);
if (operand_ty.isPtrLikeOptional()) {
const operand_llvm_ty = try self.dg.llvmType(operand_ty);
return self.builder.buildICmp(.NE, operand, operand_llvm_ty.constNull(), "");
const non_null_bit = self.builder.buildExtractValue(operand, 1, "");
if (invert) {
return self.builder.buildNot(non_null_bit, "");
} else {
return non_null_bit;
}
return self.builder.buildExtractValue(operand, 1, "");
}
fn airIsNull(self: *FuncGen, inst: Air.Inst.Index, operand_is_ptr: bool) !?*const llvm.Value {
if (self.liveness.isUnused(inst))
return null;
return self.builder.buildNot((try self.airIsNonNull(inst, operand_is_ptr)).?, "");
}
fn airIsErr(

14
src/type.zig
View File

@@ -4031,6 +4031,20 @@ pub const Type = extern union {
});
}
pub fn optional(arena: *Allocator, child_type: Type) Allocator.Error!Type {
switch (child_type.tag()) {
.single_const_pointer => return Type.Tag.optional_single_const_pointer.create(
arena,
child_type.elemType(),
),
.single_mut_pointer => return Type.Tag.optional_single_mut_pointer.create(
arena,
child_type.elemType(),
),
else => return Type.Tag.optional.create(arena, child_type),
}
}
pub fn smallestUnsignedBits(max: u64) u16 {
if (max == 0) return 0;
const base = std.math.log2(max);

8
src/value.zig
View File

@@ -1365,12 +1365,20 @@ pub const Value = extern union {
const b_field_index = b.castTag(.enum_field_index).?.data;
return a_field_index == b_field_index;
},
.opt_payload => {
const a_payload = a.castTag(.opt_payload).?.data;
const b_payload = b.castTag(.opt_payload).?.data;
var buffer: Type.Payload.ElemType = undefined;
return eql(a_payload, b_payload, ty.optionalChild(&buffer));
},
.elem_ptr => @panic("TODO: Implement more pointer eql cases"),
.field_ptr => @panic("TODO: Implement more pointer eql cases"),
.eu_payload_ptr => @panic("TODO: Implement more pointer eql cases"),
.opt_payload_ptr => @panic("TODO: Implement more pointer eql cases"),
else => {},
}
} else if (a_tag == .null_value or b_tag == .null_value) {
return false;
}
if (a.pointerDecl()) |a_decl| {

29
test/behavior/optional.zig
View File

@@ -44,3 +44,32 @@ test "optional pointer to size zero struct" {
var o: ?*EmptyStruct = &e;
try expect(o != null);
}
test "equality compare optional pointers" {
try testNullPtrsEql();
comptime try testNullPtrsEql();
}
fn testNullPtrsEql() !void {
var number: i32 = 1234;
var x: ?*i32 = null;
var y: ?*i32 = null;
try expect(x == y);
y = &number;
try expect(x != y);
try expect(x != &number);
try expect(&number != x);
x = &number;
try expect(x == y);
try expect(x == &number);
try expect(&number == x);
}
test "optional with void type" {
const Foo = struct {
x: ?void,
};
var x = Foo{ .x = null };
try expect(x.x == null);
}

29
test/behavior/optional_stage1.zig
View File

@@ -3,27 +3,6 @@ const testing = std.testing;
const expect = testing.expect;
const expectEqual = testing.expectEqual;
test "equality compare nullable pointers" {
try testNullPtrsEql();
comptime try testNullPtrsEql();
}
fn testNullPtrsEql() !void {
var number: i32 = 1234;
var x: ?*i32 = null;
var y: ?*i32 = null;
try expect(x == y);
y = &number;
try expect(x != y);
try expect(x != &number);
try expect(&number != x);
x = &number;
try expect(x == y);
try expect(x == &number);
try expect(&number == x);
}
test "address of unwrap optional" {
const S = struct {
const Foo = struct {
@@ -143,14 +122,6 @@ test "coerce an anon struct literal to optional struct" {
comptime try S.doTheTest();
}
test "optional with void type" {
const Foo = struct {
x: ?void,
};
var x = Foo{ .x = null };
try expect(x.x == null);
}
test "0-bit child type coerced to optional return ptr result location" {
const S = struct {
fn doTheTest() !void {