Commit 17e07ffc6381a1650b6bac5948b9f22d24411982 | zig

author	Matthew Lugg <mlugg@mlugg.co.uk> 2026-08-06 08:07:53+01:00
committer	Matthew Lugg <mlugg@mlugg.co.uk> 2026-08-07 09:32:22+02:00
log	17e07ffc6381a1650b6bac5948b9f22d24411982
tree	3d72ff4335360dd314567cfaf822deec99a472dd
parent	21f23814383ff8060a6b983c5ff9e47b5f1853ba

llvm: represent bool as i8 in memory

Follow-up to https://codeberg.org/ziglang/zig/pulls/35711

3 files changed, 40 insertions(+), 10 deletions(-)

src
- codegen
  - llvm.zig
  - llvm
    FuncGen.zig
test
- llvm_ir.zig

src/codegen/llvm.zig+9-4

 @@ -2912,7 +2912,7 @@ pub const Object = struct {
         return switch (t.toIntern()) {
             .u0_type => unreachable, // no runtime bits
-            .u1_type => try o.intType(1, repr),
+            .u1_type, .bool_type => try o.intType(1, repr),
             .u8_type, .i8_type => try o.intType(8, repr),
             .u16_type, .i16_type => try o.intType(16, repr),
             .u29_type => try o.intType(29, repr),
 @@ -2983,7 +2983,6 @@ pub const Object = struct {
                 // @foo = external global i8
                 return .i8;
             },
-            .bool_type => .i1,
             .anyerror_type => try o.errorIntType(repr),
             .void_type => unreachable, // no runtime bits
             .type_type => unreachable, // no runtime bits
 @@ -3472,8 +3471,14 @@ pub const Object = struct {
                 .null => unreachable, // non-runtime value
                 .@"unreachable" => unreachable, // non-runtime value
-                .false => .false,
+                .false => switch (repr) {
-                .true => .true,
+                    .as_value => .false,
+                    .in_memory, .memory_access => try o.builder.intConst(.i8, 0),
+                },
+                .true => switch (repr) {
+                    .as_value => .true,
+                    .in_memory, .memory_access => try o.builder.intConst(.i8, 1),
+                },
             },
             .enum_literal => unreachable, // non-runtime value
             .@"extern" => unreachable, // non-runtime value

src/codegen/llvm/FuncGen.zig+11-6

 @@ -2950,12 +2950,11 @@ fn airIsErr(
         if (operand_is_ptr and operand_ty.isVolatilePtr(zcu)) .@"volatile" else .normal;
     if (err_union_ty.errorUnionSet(zcu).errorSetIsEmpty(zcu)) {
-        const val: Builder.Constant = switch (cond) {
+        return switch (cond) {
             .eq => .true, // 0 == 0
             .ne => .false, // 0 != 0
             else => unreachable,
         };
-        return val.toValue();
     }
     if (operand_is_ptr) self.maybeMarkAllowZeroAccess(operand_ty.ptrInfo(zcu));
 @@ -6666,7 +6665,10 @@ fn load(
     const llvm_value_ty = try o.lowerType(load_ty, .as_value);
     if (llvm_access_ty != llvm_value_ty) {
-        assert(load_ty.isAbiInt(zcu));
+        const signedness: std.lang.Signedness = switch (load_ty.toIntern()) {
+            .bool_type => .unsigned,
+            else => load_ty.intInfo(zcu).signedness,
+        };
         // `load_ty` is an integer type with padding bits. In theory, we shouldn't need any special
         // handling for these, as LLVM's documented semantics are a valid implementation of Zig's
         // semantics. However:
 @@ -6685,7 +6687,7 @@ fn load(
         // implemented, but until then, do a normal trunc for packed types.
         return fg.wip.cast(switch (load_ty.zigTypeTag(zcu)) {
             .@"struct", .@"union" => .trunc,
-            else => switch (load_ty.intInfo(zcu).signedness) {
+            else => switch (signedness) {
                 .unsigned => .@"trunc nuw",
                 .signed => .@"trunc nsw",
             },
 @@ -6740,10 +6742,13 @@ fn store(
     const llvm_value_ty = try o.lowerType(elem_ty, .as_value);
     if (llvm_access_ty != llvm_value_ty) {
-        assert(elem_ty.isAbiInt(zcu));
+        const signedness: std.lang.Signedness = switch (elem_ty.toIntern()) {
+            .bool_type => .unsigned,
+            else => elem_ty.intInfo(zcu).signedness,
+        };
         // `elem_ty` is an integer type with padding bits, so we need to handle it specially---see
         // the corresponding comment in `FuncGen.load` for more details.
-        const extended = try fg.wip.cast(switch (elem_ty.intInfo(zcu).signedness) {
+        const extended = try fg.wip.cast(switch (signedness) {
             .unsigned => .zext,
             .signed => .sext,
         }, elem, llvm_access_ty, "");

test/llvm_ir.zig+20

...	@@ -116,6 +116,26 @@ pub fn addCases(cases: *tests.LlvmIrContext) void {	...	@@ -116,6 +116,26 @@ pub fn addCases(cases: *tests.LlvmIrContext) void {
116	"null_pointer_is_valid",	116	"null_pointer_is_valid",
117	"store i16 42, ptr",	117	"store i16 42, ptr",
118	}, .{});	118	}, .{});
		119
		120	cases.addMatches("load and store bool",
		121	\\export fn foo(a: bool, b: align(2) bool) void {
		122	\\ const tmp = a.*;
		123	\\ a.* = b.*;
		124	\\ b.* = tmp;
		125	\\}
		126	, &.{
		127	// TODO: this should all be one multiline string literal, but `-femit-llvm-ir` is currently
		128	// emitting CRLF on Windows, which is a pain to handle here. In future that option will emit
		129	// unoptimized LLVM IR emitted directly from Zig, so that bug will go away.
		130	" %3 = load i8, ptr %0, align 1",
		131	" %4 = trunc nuw i8 %3 to i1",
		132	" %5 = load i8, ptr %1, align 2",
		133	" %6 = trunc nuw i8 %5 to i1",
		134	" %7 = zext i1 %6 to i8",
		135	" store i8 %7, ptr %0, align 1",
		136	" %8 = zext i1 %4 to i8",
		137	" store i8 %8, ptr %1, align 2",
		138	}, .{ .strip = true });
119	}	139	}
120		140
121	const std = @import("std");	141	const std = @import("std");