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Sema: allow tail calls of function pointers

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Resolves: #22474
This commit is contained in:
mlugg 2025-01-12 20:55:30 +00:00 committed by Matthew Lugg
parent 15fe999572
commit f78f9388fe
4 changed files with 110 additions and 74 deletions
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8
src/Sema.zig
View File

@ -7983,7 +7983,13 @@ fn analyzeCall(
}
if (call_tag == .call_always_tail) {
return sema.handleTailCall(block, call_src, sema.typeOf(runtime_func), result);
const func_or_ptr_ty = sema.typeOf(runtime_func);
const runtime_func_ty = switch (func_or_ptr_ty.zigTypeTag(zcu)) {
.@"fn" => func_or_ptr_ty,
.pointer => func_or_ptr_ty.childType(zcu),
else => unreachable,
};
return sema.handleTailCall(block, call_src, runtime_func_ty, result);
}
if (resolved_ret_ty.toIntern() == .noreturn_type) {

1
test/behavior.zig
View File

@ -17,7 +17,6 @@ test {
_ = @import("behavior/byteswap.zig");
_ = @import("behavior/byval_arg_var.zig");
_ = @import("behavior/call.zig");
_ = @import("behavior/call_tail.zig");
_ = @import("behavior/cast.zig");
_ = @import("behavior/cast_int.zig");
_ = @import("behavior/comptime_memory.zig");

103
test/behavior/call.zig
View File

@ -651,3 +651,106 @@ test "function call with cast to anyopaque pointer" {
};
Foo.bar(Foo.t);
}
test "arguments pointed to on stack into tailcall" {
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_c and builtin.os.tag == .windows) return error.SkipZigTest; // MSVC doesn't support always tail calls
switch (builtin.cpu.arch) {
.wasm32,
.mips,
.mipsel,
.mips64,
.mips64el,
.powerpc,
.powerpcle,
.powerpc64,
.powerpc64le,
=> return error.SkipZigTest,
else => {},
}
const S = struct {
var base: usize = undefined;
var result_off: [7]usize = undefined;
var result_len: [7]usize = undefined;
var result_index: usize = 0;
noinline fn insertionSort(data: []u64) void {
result_off[result_index] = @intFromPtr(data.ptr) - base;
result_len[result_index] = data.len;
result_index += 1;
if (data.len > 1) {
var least_i: usize = 0;
var i: usize = 1;
while (i < data.len) : (i += 1) {
if (data[i] < data[least_i])
least_i = i;
}
std.mem.swap(u64, &data[0], &data[least_i]);
// there used to be a bug where
// `data[1..]` is created on the stack
// and pointed to by the first argument register
// then stack is invalidated by the tailcall and
// overwritten by callee
// https://github.com/ziglang/zig/issues/9703
return @call(.always_tail, insertionSort, .{data[1..]});
}
}
};
var data = [_]u64{ 1, 6, 2, 7, 1, 9, 3 };
S.base = @intFromPtr(&data);
S.insertionSort(data[0..]);
try expect(S.result_len[0] == 7);
try expect(S.result_len[1] == 6);
try expect(S.result_len[2] == 5);
try expect(S.result_len[3] == 4);
try expect(S.result_len[4] == 3);
try expect(S.result_len[5] == 2);
try expect(S.result_len[6] == 1);
try expect(S.result_off[0] == 0);
try expect(S.result_off[1] == 8);
try expect(S.result_off[2] == 16);
try expect(S.result_off[3] == 24);
try expect(S.result_off[4] == 32);
try expect(S.result_off[5] == 40);
try expect(S.result_off[6] == 48);
}
test "tail call function pointer" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_llvm) {
if (builtin.cpu.arch.isMIPS() or builtin.cpu.arch.isPowerPC() or builtin.cpu.arch.isWasm()) {
return error.SkipZigTest;
}
}
if (builtin.zig_backend == .stage2_c and builtin.os.tag == .windows) return error.SkipZigTest; // MSVC doesn't support always tail calls
const S = struct {
fn foo(n: u8) void {
if (n == 0) return;
const other: *const fn (u8) void = &bar;
return @call(.always_tail, other, .{n - 1});
}
fn bar(n: u8) void {
var other: *const fn (u8) void = undefined;
other = &foo; // runtime-known pointer
return @call(.always_tail, other, .{n});
}
};
S.foo(100);
}

72
test/behavior/call_tail.zig
View File

@ -1,72 +0,0 @@
const builtin = @import("builtin");
const std = @import("std");
const expect = std.testing.expect;
var base: usize = undefined;
var result_off: [7]usize = undefined;
var result_len: [7]usize = undefined;
var result_index: usize = 0;
noinline fn insertionSort(data: []u64) void {
result_off[result_index] = @intFromPtr(data.ptr) - base;
result_len[result_index] = data.len;
result_index += 1;
if (data.len > 1) {
var least_i: usize = 0;
var i: usize = 1;
while (i < data.len) : (i += 1) {
if (data[i] < data[least_i])
least_i = i;
}
std.mem.swap(u64, &data[0], &data[least_i]);
// there used to be a bug where
// `data[1..]` is created on the stack
// and pointed to by the first argument register
// then stack is invalidated by the tailcall and
// overwritten by callee
// https://github.com/ziglang/zig/issues/9703
return @call(.always_tail, insertionSort, .{data[1..]});
}
}
test "arguments pointed to on stack into tailcall" {
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
switch (builtin.cpu.arch) {
.wasm32,
.mips,
.mipsel,
.mips64,
.mips64el,
.powerpc,
.powerpcle,
.powerpc64,
.powerpc64le,
=> return error.SkipZigTest,
else => {},
}
if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_c and builtin.os.tag == .windows) return error.SkipZigTest; // MSVC doesn't support always tail calls
var data = [_]u64{ 1, 6, 2, 7, 1, 9, 3 };
base = @intFromPtr(&data);
insertionSort(data[0..]);
try expect(result_len[0] == 7);
try expect(result_len[1] == 6);
try expect(result_len[2] == 5);
try expect(result_len[3] == 4);
try expect(result_len[4] == 3);
try expect(result_len[5] == 2);
try expect(result_len[6] == 1);
try expect(result_off[0] == 0);
try expect(result_off[1] == 8);
try expect(result_off[2] == 16);
try expect(result_off[3] == 24);
try expect(result_off[4] == 32);
try expect(result_off[5] == 40);
try expect(result_off[6] == 48);
}