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Fix llvmFieldIndex for zero sized fields

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It is possible for Zig to emit field ptr instructions to fields whos
type is zero sized. In this case llvm should return a pointer which
points to the next none zero sized parameter.
This commit is contained in:
Jimmi Holst Christensen
2022-01-07 19:02:24 +01:00
parent f78d3b27ca
commit f48f687c05
1 changed files with 35 additions and 19 deletions
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54
src/codegen/llvm.zig
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@@ -2647,7 +2647,7 @@ pub const FuncGen = struct {
switch (struct_ty.zigTypeTag()) {
.Struct => {
var ptr_ty_buf: Type.Payload.Pointer = undefined;
const llvm_field_index = llvmFieldIndex(struct_ty, field_index, target, &ptr_ty_buf);
const llvm_field_index = llvmFieldIndex(struct_ty, field_index, target, &ptr_ty_buf).?;
const field_ptr = self.builder.buildStructGEP(struct_llvm_val, llvm_field_index, "");
const field_ptr_ty = Type.initPayload(&ptr_ty_buf.base);
return self.load(field_ptr, field_ptr_ty);
@@ -4354,8 +4354,18 @@ pub const FuncGen = struct {
.Struct => {
const target = self.dg.module.getTarget();
var ty_buf: Type.Payload.Pointer = undefined;
const llvm_field_index = llvmFieldIndex(struct_ty, field_index, target, &ty_buf);
return self.builder.buildStructGEP(struct_ptr, llvm_field_index, "");
if (llvmFieldIndex(struct_ty, field_index, target, &ty_buf)) |llvm_field_index| {
return self.builder.buildStructGEP(struct_ptr, llvm_field_index, "");
} else {
// If we found no index then this means this is a zero sized field at the
// end of the struct. Treat our struct pointer as an array of two and get
// the index to the element at index `1` to get a pointer to the end of
// the struct.
const llvm_usize = try self.dg.llvmType(Type.usize);
const llvm_index = llvm_usize.constInt(1, .False);
const indices: [1]*const llvm.Value = .{llvm_index};
return self.builder.buildInBoundsGEP(struct_ptr, &indices, indices.len, "");
}
},
.Union => return self.unionFieldPtr(inst, struct_ptr, struct_ty, field_index),
else => unreachable,
@@ -4750,32 +4760,37 @@ fn toLlvmCallConv(cc: std.builtin.CallingConvention, target: std.Target) llvm.Ca
};
}
/// Take into account 0 bit fields.
/// Take into account 0 bit fields. Returns null if an llvm field could not be found. This only
/// happends if you want the field index of a zero sized field at the end of the struct.
fn llvmFieldIndex(
ty: Type,
field_index: u32,
target: std.Target,
ptr_pl_buf: *Type.Payload.Pointer,
) c_uint {
) ?c_uint {
const struct_obj = ty.castTag(.@"struct").?.data;
if (struct_obj.layout != .Packed) {
var llvm_field_index: c_uint = 0;
for (struct_obj.fields.values()) |field, i| {
if (!field.ty.hasCodeGenBits()) continue;
if (i == field_index) {
ptr_pl_buf.* = .{
.data = .{
.pointee_type = field.ty,
.@"align" = field.normalAlignment(target),
.@"addrspace" = .generic,
},
};
return llvm_field_index;
if (!field.ty.hasCodeGenBits())
continue;
if (field_index > i) {
llvm_field_index += 1;
continue;
}
llvm_field_index += 1;
ptr_pl_buf.* = .{
.data = .{
.pointee_type = field.ty,
.@"align" = field.normalAlignment(target),
.@"addrspace" = .generic,
},
};
return llvm_field_index;
} else {
// We did not find an llvm field that corrispons to this zig field.
return null;
}
unreachable;
}
// Our job here is to return the host integer field index.
@@ -4784,7 +4799,8 @@ fn llvmFieldIndex(
var running_bits: u16 = 0;
var llvm_field_index: c_uint = 0;
for (struct_obj.fields.values()) |field, i| {
if (!field.ty.hasCodeGenBits()) continue;
if (!field.ty.hasCodeGenBits())
continue;
const field_align = field.packedAlignment();
if (field_align == 0) {