Commit 708894cf9903bab2e9b0dde0b609a6cc7cc55ffd | zig

author	Andrew Kelley <andrew@ziglang.org> 2024-05-01 17:14:24-07:00
committer	Andrew Kelley <andrew@ziglang.org> 2024-05-08 19:37:29-07:00
log	708894cf9903bab2e9b0dde0b609a6cc7cc55ffd
tree	a161dbfb600fef3c647a038e4dcbd142e2389f76
parent	6730b366a059a83d64f66644bf49d69cb31a6a08

add a debug subcommand for printing LLVM integer type alignment

Useful when debugging why upgrading from LLVM 17 to 18 caused C ABI
regressions. Turns out LLVM 18 does the following insane thing:

```diff
-[nix-shell:~/dev/zig/build-llvm17]$ stage4/bin/zig llvm-ints i386-linux-musl
+[nix-shell:~/src/zig/build-llvm18]$ stage4/bin/zig llvm-ints i386-linux-musl
 LLVMABIAlignmentOfType(i1) == 1
 LLVMABIAlignmentOfType(i8) == 1
 LLVMABIAlignmentOfType(i16) == 2
 LLVMABIAlignmentOfType(i32) == 4
 LLVMABIAlignmentOfType(i64) == 4
-LLVMABIAlignmentOfType(i128) == 4
-LLVMABIAlignmentOfType(i256) == 4
+LLVMABIAlignmentOfType(i128) == 16
+LLVMABIAlignmentOfType(i256) == 16
```

2 files changed, 56 insertions(+), 0 deletions(-)

src
- codegen
  - llvm
    bindings.zig
- main.zig

src/codegen/llvm/bindings.zig+11

...	...	@@ -43,6 +43,9 @@ pub const Context = opaque {
43	43
44	44	pub const getBrokenDebugInfo = ZigLLVMGetBrokenDebugInfo;
45	45	extern fn ZigLLVMGetBrokenDebugInfo(C: *Context) bool;
	46
	47	pub const intType = LLVMIntTypeInContext;
	48	extern fn LLVMIntTypeInContext(C: Context, NumBits: c_uint) Type;
46	49	};
47	50
48	51	pub const Module = opaque {
...	...	@@ -96,13 +99,21 @@ pub const TargetMachine = opaque {
96	99	llvm_ir_filename: ?[*:0]const u8,
97	100	bitcode_filename: ?[*:0]const u8,
98	101	) bool;
	102
	103	pub const createTargetDataLayout = LLVMCreateTargetDataLayout;
	104	extern fn LLVMCreateTargetDataLayout(TargetMachine) TargetData;
99	105	};
100	106
101	107	pub const TargetData = opaque {
102	108	pub const dispose = LLVMDisposeTargetData;
103	109	extern fn LLVMDisposeTargetData(*TargetData) void;
	110
	111	pub const abiAlignmentOfType = LLVMABIAlignmentOfType;
	112	extern fn LLVMABIAlignmentOfType(TD: TargetData, Ty: Type) c_uint;
104	113	};
105	114
	115	pub const Type = opaque {};
	116
106	117	pub const CodeModel = enum(c_int) {
107	118	Default,
108	119	JITDefault,

src/main.zig+45

...	...	@@ -118,6 +118,7 @@ const debug_usage = normal_usage ++
118	118	\\ changelist Compute mappings from old ZIR to new ZIR
119	119	\\ dump-zir Dump a file containing cached ZIR
120	120	\\ detect-cpu Compare Zig's CPU feature detection vs LLVM
	121	\\ llvm-ints Dump a list of LLVMABIAlignmentOfType for all integers
121	122	\\
122	123	;
123	124
...	...	@@ -359,6 +360,8 @@ fn mainArgs(gpa: Allocator, arena: Allocator, args: []const []const u8) !void {
359	360	return cmdChangelist(gpa, arena, cmd_args);
360	361	} else if (build_options.enable_debug_extensions and mem.eql(u8, cmd, "dump-zir")) {
361	362	return cmdDumpZir(gpa, arena, cmd_args);
	363	} else if (build_options.enable_debug_extensions and mem.eql(u8, cmd, "llvm-ints")) {
	364	return cmdDumpLlvmInts(gpa, arena, cmd_args);
362	365	} else {
363	366	std.log.info("{s}", .{usage});
364	367	fatal("unknown command: {s}", .{args[1]});
...	...	@@ -6292,6 +6295,48 @@ fn printCpu(cpu: std.Target.Cpu) !void {
6292	6295	try bw.flush();
6293	6296	}
6294	6297
	6298	fn cmdDumpLlvmInts(
	6299	gpa: Allocator,
	6300	arena: Allocator,
	6301	args: []const []const u8,
	6302	) !void {
	6303	_ = gpa;
	6304
	6305	if (!build_options.have_llvm)
	6306	fatal("compiler does not use LLVM; cannot dump LLVM integer sizes", .{});
	6307
	6308	const triple = try arena.dupeZ(u8, args[0]);
	6309
	6310	const llvm = @import("codegen/llvm/bindings.zig");
	6311
	6312	for ([_]std.Target.Cpu.Arch{ .aarch64, .x86 }) \|arch\| {
	6313	@import("codegen/llvm.zig").initializeLLVMTarget(arch);
	6314	}
	6315
	6316	const target: *llvm.Target = t: {
	6317	var target: *llvm.Target = undefined;
	6318	var error_message: [*:0]const u8 = undefined;
	6319	if (llvm.Target.getFromTriple(triple, &target, &error_message) != .False) @panic("bad");
	6320	break :t target;
	6321	};
	6322	const tm = llvm.TargetMachine.create(target, triple, null, null, .None, .Default, .Default, false, false, .Default, null);
	6323	const dl = tm.createTargetDataLayout();
	6324	const context = llvm.Context.create();
	6325
	6326	var bw = io.bufferedWriter(io.getStdOut().writer());
	6327	const stdout = bw.writer();
	6328
	6329	for ([_]u16{ 1, 8, 16, 32, 64, 128, 256 }) \|bits\| {
	6330	const int_type = context.intType(bits);
	6331	const alignment = dl.abiAlignmentOfType(int_type);
	6332	try stdout.print("LLVMABIAlignmentOfType(i{d}) == {d}\n", .{ bits, alignment });
	6333	}
	6334
	6335	try bw.flush();
	6336
	6337	return cleanExit();
	6338	}
	6339
6295	6340	/// This is only enabled for debug builds.
6296	6341	fn cmdDumpZir(
6297	6342	gpa: Allocator,