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llvm: fix lowering of packed struct constants

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The big-endian logic here was simply incorrect. Luckily, it was also
overcomplicated; after calling `Value.writeToPackedMemory`, there is a
method on `std.math.big.int.Mutable` which just does the correct
endianness load for us.
This commit is contained in:
Matthew Lugg 2025-11-17 01:36:07 +01:00 committed by Alex Rønne Petersen
parent 891f187032
commit a319211eee
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1 changed files with 9 additions and 22 deletions
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31
src/codegen/llvm.zig
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@ -3651,35 +3651,22 @@ pub const Object = struct {
.opt => {}, // pointer like optional expected
else => unreachable,
}
const bits = ty.bitSize(zcu);
const bytes: usize = @intCast(std.mem.alignForward(u64, bits, 8) / 8);
var stack = std.heap.stackFallback(32, o.gpa);
const allocator = stack.get();
const limbs = try allocator.alloc(
std.math.big.Limb,
std.mem.alignForward(usize, bytes, @sizeOf(std.math.big.Limb)) /
@sizeOf(std.math.big.Limb),
);
const bits: usize = @intCast(ty.bitSize(zcu));
const buffer = try allocator.alloc(u8, (bits + 7) / 8);
defer allocator.free(buffer);
const limbs = try allocator.alloc(std.math.big.Limb, std.math.big.int.calcTwosCompLimbCount(bits));
defer allocator.free(limbs);
@memset(limbs, 0);
val.writeToPackedMemory(ty, pt, std.mem.sliceAsBytes(limbs)[0..bytes], 0) catch unreachable;
val.writeToPackedMemory(ty, pt, buffer, 0) catch unreachable;
if (builtin.target.cpu.arch.endian() == .little) {
if (target.cpu.arch.endian() == .big)
std.mem.reverse(u8, std.mem.sliceAsBytes(limbs)[0..bytes]);
} else if (target.cpu.arch.endian() == .little) {
for (limbs) |*limb| {
limb.* = std.mem.nativeToLittle(usize, limb.*);
}
}
var big: std.math.big.int.Mutable = .init(limbs, 0);
big.readTwosComplement(buffer, bits, target.cpu.arch.endian(), .unsigned);
return o.builder.bigIntConst(llvm_int_ty, .{
.limbs = limbs,
.positive = true,
});
return o.builder.bigIntConst(llvm_int_ty, big.toConst());
}
fn lowerValue(o: *Object, pt: Zcu.PerThread, arg_val: InternPool.Index) Error!Builder.Constant {