Commit 995fd7314c

Andrew Kelley <andrew@ziglang.org>
2020-07-24 23:06:44
Revert "Support taking extern pointers at comptime"
This reverts commit d3ebd428650748e60db70dd2171cc044855814b1. This caused a build failure on multiple targets.
1 parent 978a38e
src/codegen.cpp
@@ -7754,13 +7754,6 @@ static LLVMValueRef gen_const_val(CodeGen *g, ZigValue *const_val, const char *n
 }
 
 static void render_const_val(CodeGen *g, ZigValue *const_val, const char *name) {
-    if (const_val->special == ConstValSpecialRuntime) {
-        // `const_val` refers to an extern variable. Don't generate an `LLVMValueRef` for
-        // the variable. We shouldn't call `LLVMSetInitializer` on it either.
-        assert(const_val->llvm_global);
-        return;
-    }
-
     if (!const_val->llvm_value)
         const_val->llvm_value = gen_const_val(g, const_val, name);
 
@@ -7769,13 +7762,6 @@ static void render_const_val(CodeGen *g, ZigValue *const_val, const char *name)
 }
 
 static void render_const_val_global(CodeGen *g, ZigValue *const_val, const char *name) {
-    if (const_val->special == ConstValSpecialRuntime) {
-        // `const_val` refers to an extern variable. `llvm_global` should already
-        // have been created by an earlier codegen pass.
-        assert(const_val->llvm_global);
-        return;
-    }
-
     if (!const_val->llvm_global) {
         LLVMTypeRef type_ref = const_val->llvm_value ?
             LLVMTypeOf(const_val->llvm_value) : get_llvm_type(g, const_val->type);
@@ -7905,39 +7891,6 @@ static void do_code_gen(CodeGen *g) {
 
     generate_error_name_table(g);
 
-    // Create extern variables
-    for (size_t i = 0; i < g->global_vars.length; i += 1) {
-        TldVar *tld_var = g->global_vars.at(i);
-        ZigVar *var = tld_var->var;
-
-        bool externally_initialized = var->decl_node->data.variable_declaration.expr == nullptr;
-        if (!externally_initialized) {
-            continue;
-        }
-
-        assert(var->decl_node->data.variable_declaration.is_extern);
-        const char *symbol_name = var->name;
-
-        LLVMValueRef global_value;
-        LLVMValueRef existing_llvm_var = LLVMGetNamedGlobal(g->module, symbol_name);
-        if (existing_llvm_var) {
-            global_value = LLVMConstBitCast(existing_llvm_var,
-                    LLVMPointerType(get_llvm_type(g, var->var_type), 0));
-        } else {
-            global_value = LLVMAddGlobal(g->module, get_llvm_type(g, var->var_type), symbol_name);
-            // TODO debug info for the extern variable
-
-            LLVMSetLinkage(global_value, LLVMExternalLinkage);
-            maybe_import_dll(g, global_value, GlobalLinkageIdStrong);
-            LLVMSetAlignment(global_value, var->align_bytes);
-            LLVMSetGlobalConstant(global_value, var->gen_is_const);
-            set_global_tls(g, var, global_value);
-        }
-
-        var->value_ref = global_value;
-        var->const_value->llvm_global = global_value;
-    }
-
     // Generate module level variables
     for (size_t i = 0; i < g->global_vars.length; i += 1) {
         TldVar *tld_var = g->global_vars.at(i);
@@ -8003,12 +7956,28 @@ static void do_code_gen(CodeGen *g) {
             linkage = global_export->linkage;
         }
 
+        LLVMValueRef global_value;
         bool externally_initialized = var->decl_node->data.variable_declaration.expr == nullptr;
-        if (!externally_initialized) {
+        if (externally_initialized) {
+            LLVMValueRef existing_llvm_var = LLVMGetNamedGlobal(g->module, symbol_name);
+            if (existing_llvm_var) {
+                global_value = LLVMConstBitCast(existing_llvm_var,
+                        LLVMPointerType(get_llvm_type(g, var->var_type), 0));
+            } else {
+                global_value = LLVMAddGlobal(g->module, get_llvm_type(g, var->var_type), symbol_name);
+                // TODO debug info for the extern variable
+
+                LLVMSetLinkage(global_value, to_llvm_linkage(linkage));
+                maybe_import_dll(g, global_value, GlobalLinkageIdStrong);
+                LLVMSetAlignment(global_value, var->align_bytes);
+                LLVMSetGlobalConstant(global_value, var->gen_is_const);
+                set_global_tls(g, var, global_value);
+            }
+        } else {
             bool exported = (linkage != GlobalLinkageIdInternal);
             render_const_val(g, var->const_value, symbol_name);
             render_const_val_global(g, var->const_value, symbol_name);
-            LLVMValueRef global_value = var->const_value->llvm_global;
+            global_value = var->const_value->llvm_global;
 
             if (exported) {
                 LLVMSetLinkage(global_value, to_llvm_linkage(linkage));
@@ -8028,9 +7997,10 @@ static void do_code_gen(CodeGen *g) {
 
             LLVMSetGlobalConstant(global_value, var->gen_is_const);
             set_global_tls(g, var, global_value);
-            var->value_ref = global_value;
         }
 
+        var->value_ref = global_value;
+
         for (size_t export_i = 1; export_i < var->export_list.length; export_i += 1) {
             GlobalExport *global_export = &var->export_list.items[export_i];
             LLVMAddAlias(g->module, LLVMTypeOf(var->value_ref), var->value_ref, buf_ptr(&global_export->name));
src/ir.cpp
@@ -19894,34 +19894,30 @@ static IrInstGen *ir_get_var_ptr(IrAnalyze *ira, IrInst *source_instr, ZigVar *v
     IrInstGen *result = ir_build_var_ptr_gen(ira, source_instr, var);
     result->value->type = var_ptr_type;
 
-    bool is_local_var = !var->decl_node->data.variable_declaration.is_extern &&
-        var->const_value->special == ConstValSpecialRuntime;
-
-    // The address of a thread-local variable can't be resolved even by a linker because
-    // it's dependent on the current thread. The concept of current thread doesn't exist
-    // at compile time, so even if we had a symbolic (i.e., relocatable) representation
-    // of a pointer to a thread-local variable, there would be no ways to make use of it
-    // in a meaningful way.
-    //
-    // The same goes for local variables - They are stored in a stack frame, whose
-    // instance doesn't even exist at compile/link time.
-    if (!var->is_thread_local && !is_local_var) {
+    if (!linkage_makes_it_runtime && !var->is_thread_local && value_is_comptime(var->const_value)) {
         ZigValue *val = var->const_value;
-
-        ConstPtrMut ptr_mut;
-        if (comptime_var_mem) {
-            ptr_mut = ConstPtrMutComptimeVar;
-        } else if (var->gen_is_const && !linkage_makes_it_runtime) {
-            ptr_mut = ConstPtrMutComptimeConst;
-        } else {
-            assert(!comptime_var_mem);
-            ptr_mut = ConstPtrMutRuntimeVar;
+        switch (val->special) {
+            case ConstValSpecialRuntime:
+                break;
+            case ConstValSpecialStatic: // fallthrough
+            case ConstValSpecialLazy: // fallthrough
+            case ConstValSpecialUndef: {
+                ConstPtrMut ptr_mut;
+                if (comptime_var_mem) {
+                    ptr_mut = ConstPtrMutComptimeVar;
+                } else if (var->gen_is_const) {
+                    ptr_mut = ConstPtrMutComptimeConst;
+                } else {
+                    assert(!comptime_var_mem);
+                    ptr_mut = ConstPtrMutRuntimeVar;
+                }
+                result->value->special = ConstValSpecialStatic;
+                result->value->data.x_ptr.mut = ptr_mut;
+                result->value->data.x_ptr.special = ConstPtrSpecialRef;
+                result->value->data.x_ptr.data.ref.pointee = val;
+                return result;
+            }
         }
-        result->value->special = ConstValSpecialStatic;
-        result->value->data.x_ptr.mut = ptr_mut;
-        result->value->data.x_ptr.special = ConstPtrSpecialRef;
-        result->value->data.x_ptr.data.ref.pointee = val;
-        return result;
     }
 
     bool in_fn_scope = (scope_fn_entry(var->parent_scope) != nullptr);
@@ -22292,15 +22288,12 @@ static IrInstGen *ir_analyze_struct_field_ptr(IrAnalyze *ira, IrInst* source_ins
             if (type_is_invalid(struct_val->type))
                 return ira->codegen->invalid_inst_gen;
 
-            if (ptr_val->data.x_ptr.mut != ConstPtrMutRuntimeVar) {
-                // This to allow lazy values to be resolved.
-                if ((err = ir_resolve_const_val(ira->codegen, ira->new_irb.exec,
-                    source_instr->source_node, struct_val, UndefOk)))
-                {
-                    return ira->codegen->invalid_inst_gen;
-                }
+            // This to allow lazy values to be resolved.
+            if ((err = ir_resolve_const_val(ira->codegen, ira->new_irb.exec,
+                source_instr->source_node, struct_val, UndefOk)))
+            {
+                return ira->codegen->invalid_inst_gen;
             }
-
             if (initializing && struct_val->special == ConstValSpecialUndef) {
                 struct_val->data.x_struct.fields = alloc_const_vals_ptrs(ira->codegen, struct_type->data.structure.src_field_count);
                 struct_val->special = ConstValSpecialStatic;
test/standalone/extern_ref/build.zig
@@ -1,15 +0,0 @@
-const Builder = @import("std").build.Builder;
-
-pub fn build(b: *Builder) void {
-    const mode = b.standardReleaseOptions();
-
-    const obj = b.addStaticLibrary("obj", "obj.zig");
-    obj.setBuildMode(mode);
-
-    const main = b.addTest("main.zig");
-    main.setBuildMode(mode);
-    main.linkLibrary(obj);
-
-    const test_step = b.step("test", "Test it");
-    test_step.dependOn(&main.step);
-}
test/standalone/extern_ref/main.zig
@@ -1,120 +0,0 @@
-const std = @import("std");
-const eql = std.mem.eql;
-
-// These are defined in `obj.zig`
-extern var global_var: usize;
-extern const global_const: usize;
-
-const TheStruct = @import("./types.zig").TheStruct;
-extern var global_var_struct: TheStruct;
-extern const global_const_struct: TheStruct;
-
-const TheUnion = @import("./types.zig").TheUnion;
-extern var global_var_union: TheUnion;
-extern const global_const_union: TheUnion;
-
-extern var global_var_array: [4]u32;
-extern const global_const_array: [4]u32;
-
-// Take the pointers to external entities as constant values
-const p_global_var = &global_var;
-const p_global_const = &global_const;
-
-test "access the external integers" {
-    std.testing.expect(p_global_var.* == 2);
-    std.testing.expect(p_global_const.* == 422);
-}
-
-const p_global_var_struct = &global_var_struct;
-const p_global_const_struct = &global_const_struct;
-
-const p_global_var_struct_val = &global_var_struct.value;
-const p_global_const_struct_val = &global_const_struct.value;
-
-const p_global_var_struct_array = &global_var_struct.array;
-const p_global_const_struct_array = &global_const_struct.array;
-
-const p_global_var_struct_array2 = global_var_struct.array[1..3];
-const p_global_const_struct_array2 = global_const_struct.array[1..3];
-
-const p_global_var_struct_array3 = &global_var_struct.array[1];
-const p_global_const_struct_array3 = &global_const_struct.array[1];
-
-test "access the external integers in a struct through comptime ptrs" {
-    std.testing.expect(p_global_var_struct.value == 2);
-    std.testing.expect(p_global_const_struct.value == 422);
-
-    std.testing.expect(p_global_var_struct_val.* == 2);
-    std.testing.expect(p_global_const_struct_val.* == 422);
-}
-
-test "access the external arrays in a struct through comptime ptrs" {
-    // TODO
-    // std.testing.expect(eql(u32, &p_global_var_struct.array, &[_]u32{1, 2, 3, 4}));
-    // std.testing.expect(eql(u32, &p_global_const_struct.array, &[_]u32{5, 6, 7, 8}));
-
-    // TODO
-    // std.testing.expect(eql(u32, p_global_var_struct_array, &[_]u32{1, 2, 3, 4}));
-    // std.testing.expect(eql(u32, p_global_const_struct_array, &[_]u32{5, 6, 7, 8}));
-
-    // TODO
-    // std.testing.expect(eql(u32, p_global_var_struct_array2, &[_]u32{2, 3}));
-    // std.testing.expect(eql(u32, p_global_const_struct_array2, &[_]u32{6, 7}));
-
-    // TODO
-    // std.testing.expect(p_global_var_struct_array3.* == 2);
-    // std.testing.expect(p_global_const_struct_array3.* == 6);
-}
-
-test "access the external integers with indirection through comptime ptrs" {
-    std.testing.expect(p_global_var_struct.p_value.* == 3);
-    std.testing.expect(p_global_const_struct.p_value.* == 423);
-}
-
-const p_global_var_struct_inner_val = &global_var_struct.inner.value;
-const p_global_const_struct_inner_val = &global_const_struct.inner.value;
-
-test "access the external integers in a nested struct through comptime ptrs" {
-    // TODO
-    // std.testing.expect(p_global_var_struct_inner_val.* == 4);
-    // std.testing.expect(p_global_const_struct_inner_val.* == 424);
-}
-
-const p_global_var_union = &global_var_union;
-const p_global_const_union = &global_const_union;
-
-const p_global_var_union_val = &global_var_union.U32;
-const p_global_const_union_val = &global_const_union.U32;
-
-test "access the external integers in a union through comptime ptrs" {
-    std.testing.expect(p_global_var_union.U32 == 10);
-    std.testing.expect(p_global_const_union.U32 == 20);
-
-    // TODO
-    // std.testing.expect(p_global_var_union_val.* == 10);
-    // std.testing.expect(p_global_const_union_val.* == 20);
-}
-
-const p_global_var_array = &global_var_array;
-const p_global_const_array = &global_const_array;
-
-const p_global_var_array2 = global_var_array[1..3];
-const p_global_const_array2 = global_const_array[1..3];
-
-const p_global_var_array3 = &global_var_array[1];
-const p_global_const_array3 = &global_const_array[1];
-
-test "access the external arrays through comptime ptrs" {
-    std.testing.expect(eql(u32, &global_var_array, &[_]u32{1, 2, 3, 4}));
-    std.testing.expect(eql(u32, &global_const_array, &[_]u32{5, 6, 7, 8}));
-
-    std.testing.expect(eql(u32, p_global_var_array, &[_]u32{1, 2, 3, 4}));
-    std.testing.expect(eql(u32, p_global_const_array, &[_]u32{5, 6, 7, 8}));
-
-    std.testing.expect(eql(u32, p_global_var_array2, &[_]u32{2, 3}));
-    std.testing.expect(eql(u32, p_global_const_array2, &[_]u32{6, 7}));
-
-    // TODO
-    // std.testing.expect(p_global_var_array3.* == 2);
-    // std.testing.expect(p_global_const_array3.* == 6);
-}
test/standalone/extern_ref/obj.zig
@@ -1,27 +0,0 @@
-export var global_var: usize = 2;
-export const global_const: usize = 422;
-
-const TheStruct = @import("./types.zig").TheStruct;
-export var global_var_struct = TheStruct{
-    .value = 2,
-    .array = [_]u32{ 1, 2, 3, 4 },
-    .p_value = &@as(u32, 3),
-    .inner = .{ .value = 4 },
-};
-export const global_const_struct = TheStruct{
-    .value = 422,
-    .array = [_]u32{ 5, 6, 7, 8 },
-    .p_value = &@as(u32, 423),
-    .inner = .{ .value = 424 },
-};
-
-const TheUnion = @import("./types.zig").TheUnion;
-export var global_var_union = TheUnion{
-    .U32 = 10,
-};
-export const global_const_union = TheUnion{
-    .U32 = 20,
-};
-
-export var global_var_array = [4]u32{ 1, 2, 3, 4 };
-export const global_const_array = [4]u32{ 5, 6, 7, 8 };
test/standalone/extern_ref/types.zig
@@ -1,15 +0,0 @@
-pub const TheStruct = extern struct {
-    value: u32,
-    array: [4]u32,
-    p_value: *const u32,
-    inner: InnerStruct,
-};
-
-pub const InnerStruct = extern struct {
-    value: u32,
-};
-
-pub const TheUnion = extern union {
-    U32: u32,
-    Bool: bool,
-};
test/compile_errors.zig
@@ -7637,26 +7637,4 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
     , &[_][]const u8{
         "tmp.zig:4:9: error: expected type '*c_void', found '?*c_void'",
     });
-
-    cases.add("pointer to a local runtime `var` is not constant",
-        \\export fn get_ptr() *const u32 {
-        \\    var local_var: u32 = 42;
-        \\    return struct {
-        \\        const ptr = &local_var;
-        \\    }.ptr;
-        \\}
-    , &[_][]const u8{
-        ":4:21: error: cannot store runtime value in compile time variable",
-    });
-
-    cases.add("pointer to a local runtime `const` is not constant",
-        \\export fn get_ptr(x: u32) *const u32 {
-        \\    const local_var: u32 = x;
-        \\    return struct {
-        \\        const ptr = &local_var;
-        \\    }.ptr;
-        \\}
-    , &[_][]const u8{
-        ":4:21: error: cannot store runtime value in compile time variable",
-    });
 }
test/standalone.zig
@@ -19,7 +19,6 @@ pub fn addCases(cases: *tests.StandaloneContext) void {
     cases.addBuildFile("test/standalone/use_alias/build.zig");
     cases.addBuildFile("test/standalone/brace_expansion/build.zig");
     cases.addBuildFile("test/standalone/empty_env/build.zig");
-    cases.addBuildFile("test/standalone/extern_ref/build.zig");
     if (std.Target.current.os.tag != .wasi) {
         cases.addBuildFile("test/standalone/load_dynamic_library/build.zig");
     }