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avoid needlessly creating global constants

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This deletes some legacy cruft, and produces leaner object files.
Example:

```
var x: i32 = 1234;

export fn entry() i32 {
    return x;
}
```

This produces:

```
@x = internal unnamed_addr global i32 1234, align 4
@0 = internal unnamed_addr constant i32* @x, align 8
```

and @0 is never even used. After this commit, @0 is not produced.

This fixes a bug: Zig was creating invalid LLVM IR when one of these
globals that shouldn't exist takes the address of a thread local
variable. In LLVM 8.0.0rc2, it would produce a linker error. But
probably after my bug report is solved it will be caught by the IR
verifier.

https://bugs.llvm.org/show_bug.cgi?id=40652
This commit is contained in:
Andrew Kelley 2019-02-10 10:58:00 -05:00
parent bcbcb2e9ff
commit 7a8f391b0f
No known key found for this signature in database
GPG Key ID: 7C5F548F728501A9
1 changed files with 16 additions and 31 deletions
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47
src/codegen.cpp
View File

@ -5762,81 +5762,71 @@ static LLVMValueRef gen_const_val_ptr(CodeGen *g, ConstExprValue *const_val, con
zig_unreachable();
case ConstPtrSpecialRef:
{
render_const_val_global(g, const_val, name);
assert(const_val->global_refs != nullptr);
ConstExprValue *pointee = const_val->data.x_ptr.data.ref.pointee;
render_const_val(g, pointee, "");
render_const_val_global(g, pointee, "");
ConstExprValue *other_val = pointee;
const_val->global_refs->llvm_value = LLVMConstBitCast(other_val->global_refs->llvm_global, const_val->type->type_ref);
render_const_val_global(g, const_val, "");
const_val->global_refs->llvm_value = LLVMConstBitCast(pointee->global_refs->llvm_global, const_val->type->type_ref);
return const_val->global_refs->llvm_value;
}
case ConstPtrSpecialBaseArray:
{
render_const_val_global(g, const_val, name);
assert(const_val->global_refs != nullptr);
ConstExprValue *array_const_val = const_val->data.x_ptr.data.base_array.array_val;
size_t elem_index = const_val->data.x_ptr.data.base_array.elem_index;
assert(array_const_val->type->id == ZigTypeIdArray);
if (array_const_val->type->zero_bits) {
if (!type_has_bits(array_const_val->type)) {
// make this a null pointer
ZigType *usize = g->builtin_types.entry_usize;
const_val->global_refs->llvm_value = LLVMConstIntToPtr(LLVMConstNull(usize->type_ref),
const_val->type->type_ref);
render_const_val_global(g, const_val, "");
return const_val->global_refs->llvm_value;
}
LLVMValueRef uncasted_ptr_val = gen_const_ptr_array_recursive(g, array_const_val,
elem_index);
size_t elem_index = const_val->data.x_ptr.data.base_array.elem_index;
LLVMValueRef uncasted_ptr_val = gen_const_ptr_array_recursive(g, array_const_val, elem_index);
LLVMValueRef ptr_val = LLVMConstBitCast(uncasted_ptr_val, const_val->type->type_ref);
const_val->global_refs->llvm_value = ptr_val;
render_const_val_global(g, const_val, "");
return ptr_val;
}
case ConstPtrSpecialBaseStruct:
{
render_const_val_global(g, const_val, name);
assert(const_val->global_refs != nullptr);
ConstExprValue *struct_const_val = const_val->data.x_ptr.data.base_struct.struct_val;
assert(struct_const_val->type->id == ZigTypeIdStruct);
if (struct_const_val->type->zero_bits) {
if (!type_has_bits(struct_const_val->type)) {
// make this a null pointer
ZigType *usize = g->builtin_types.entry_usize;
const_val->global_refs->llvm_value = LLVMConstIntToPtr(LLVMConstNull(usize->type_ref),
const_val->type->type_ref);
render_const_val_global(g, const_val, "");
return const_val->global_refs->llvm_value;
}
size_t src_field_index = const_val->data.x_ptr.data.base_struct.field_index;
size_t gen_field_index =
struct_const_val->type->data.structure.fields[src_field_index].gen_index;
size_t gen_field_index = struct_const_val->type->data.structure.fields[src_field_index].gen_index;
LLVMValueRef uncasted_ptr_val = gen_const_ptr_struct_recursive(g, struct_const_val,
gen_field_index);
LLVMValueRef ptr_val = LLVMConstBitCast(uncasted_ptr_val, const_val->type->type_ref);
const_val->global_refs->llvm_value = ptr_val;
render_const_val_global(g, const_val, "");
return ptr_val;
}
case ConstPtrSpecialBaseErrorUnionCode:
{
render_const_val_global(g, const_val, name);
assert(const_val->global_refs != nullptr);
ConstExprValue *err_union_const_val = const_val->data.x_ptr.data.base_err_union_code.err_union_val;
assert(err_union_const_val->type->id == ZigTypeIdErrorUnion);
if (err_union_const_val->type->zero_bits) {
if (!type_has_bits(err_union_const_val->type)) {
// make this a null pointer
ZigType *usize = g->builtin_types.entry_usize;
const_val->global_refs->llvm_value = LLVMConstIntToPtr(LLVMConstNull(usize->type_ref),
const_val->type->type_ref);
render_const_val_global(g, const_val, "");
return const_val->global_refs->llvm_value;
}
LLVMValueRef uncasted_ptr_val = gen_const_ptr_err_union_code_recursive(g, err_union_const_val);
LLVMValueRef ptr_val = LLVMConstBitCast(uncasted_ptr_val, const_val->type->type_ref);
const_val->global_refs->llvm_value = ptr_val;
render_const_val_global(g, const_val, "");
return ptr_val;
}
case ConstPtrSpecialBaseErrorUnionPayload:
{
render_const_val_global(g, const_val, name);
assert(const_val->global_refs != nullptr);
ConstExprValue *err_union_const_val = const_val->data.x_ptr.data.base_err_union_payload.err_union_val;
assert(err_union_const_val->type->id == ZigTypeIdErrorUnion);
if (err_union_const_val->type->zero_bits) {
@ -5844,18 +5834,16 @@ static LLVMValueRef gen_const_val_ptr(CodeGen *g, ConstExprValue *const_val, con
ZigType *usize = g->builtin_types.entry_usize;
const_val->global_refs->llvm_value = LLVMConstIntToPtr(LLVMConstNull(usize->type_ref),
const_val->type->type_ref);
render_const_val_global(g, const_val, "");
return const_val->global_refs->llvm_value;
}
LLVMValueRef uncasted_ptr_val = gen_const_ptr_err_union_payload_recursive(g, err_union_const_val);
LLVMValueRef ptr_val = LLVMConstBitCast(uncasted_ptr_val, const_val->type->type_ref);
const_val->global_refs->llvm_value = ptr_val;
render_const_val_global(g, const_val, "");
return ptr_val;
}
case ConstPtrSpecialBaseOptionalPayload:
{
render_const_val_global(g, const_val, name);
assert(const_val->global_refs != nullptr);
ConstExprValue *optional_const_val = const_val->data.x_ptr.data.base_optional_payload.optional_val;
assert(optional_const_val->type->id == ZigTypeIdOptional);
if (optional_const_val->type->zero_bits) {
@ -5863,23 +5851,20 @@ static LLVMValueRef gen_const_val_ptr(CodeGen *g, ConstExprValue *const_val, con
ZigType *usize = g->builtin_types.entry_usize;
const_val->global_refs->llvm_value = LLVMConstIntToPtr(LLVMConstNull(usize->type_ref),
const_val->type->type_ref);
render_const_val_global(g, const_val, "");
return const_val->global_refs->llvm_value;
}
LLVMValueRef uncasted_ptr_val = gen_const_ptr_optional_payload_recursive(g, optional_const_val);
LLVMValueRef ptr_val = LLVMConstBitCast(uncasted_ptr_val, const_val->type->type_ref);
const_val->global_refs->llvm_value = ptr_val;
render_const_val_global(g, const_val, "");
return ptr_val;
}
case ConstPtrSpecialHardCodedAddr:
{
render_const_val_global(g, const_val, name);
assert(const_val->global_refs != nullptr);
uint64_t addr_value = const_val->data.x_ptr.data.hard_coded_addr.addr;
ZigType *usize = g->builtin_types.entry_usize;
const_val->global_refs->llvm_value = LLVMConstIntToPtr(LLVMConstInt(usize->type_ref, addr_value, false),
const_val->type->type_ref);
render_const_val_global(g, const_val, "");
const_val->global_refs->llvm_value = LLVMConstIntToPtr(
LLVMConstInt(usize->type_ref, addr_value, false), const_val->type->type_ref);
return const_val->global_refs->llvm_value;
}
case ConstPtrSpecialFunction: