Commit 7a8f391b0fa397eea4a9602a0132e0247d0f67b7 | zig

author	Andrew Kelley <andrew@ziglang.org> 2019-02-10 10:58:00-05:00
committer	Andrew Kelley <andrew@ziglang.org> 2019-02-10 11:07:00-05:00
log	7a8f391b0fa397eea4a9602a0132e0247d0f67b7
tree	bec959df7cd42b36bea7ab80c93bda4283eee155
parent	bcbcb2e9ffbfef63d3692ea45eea2e2babacc3a9
signature	Commit is signed but in an unrecognized format.

avoid needlessly creating global constants

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

1 files changed, 16 insertions(+), 31 deletions(-)

src
- codegen.cpp

src/codegen.cpp+16-31

 @@ -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(pointee->global_refs->llvm_global, const_val->type->type_ref);
-                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, "");
                 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,
+                size_t elem_index = const_val->data.x_ptr.data.base_array.elem_index;
-                        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 =
+                size_t gen_field_index = struct_const_val->type->data.structure.fields[src_field_index].gen_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->global_refs->llvm_value = LLVMConstIntToPtr(
-                        const_val->type->type_ref);
+                        LLVMConstInt(usize->type_ref, addr_value, false), const_val->type->type_ref);
-                render_const_val_global(g, const_val, "");
                 return const_val->global_refs->llvm_value;
             }
         case ConstPtrSpecialFunction: