refactor ir.cpp

Analysis functions no longer return `ZigType *`. Instead they
return `IrInstruction *`.

src/all_types.hpp

@@ -1690,6 +1690,7 @@ struct CodeGen {
     Buf cache_dir;
 
     IrInstruction *invalid_instruction;
+    IrInstruction *unreach_instruction;
 
     ConstExprValue const_void_val;
     ConstExprValue panic_msg_vals[PanicMsgIdCount];
@@ -2183,7 +2184,10 @@ struct IrInstruction {
     // if ref_count is zero and the instruction has no side effects,
     // the instruction can be omitted in codegen
     size_t ref_count;
-    IrInstruction *other;
+    // When analyzing IR, instructions that point to this instruction in the "old ir"
+    // can find the instruction that corresponds to this value in the "new ir"
+    // with this child field.
+    IrInstruction *child;
     IrBasicBlock *owner_bb;
     // true if this instruction was generated by zig and not from user code
     bool is_gen;

src/analyze.cpp

@@ -5512,10 +5512,19 @@ Error type_resolve(CodeGen *g, ZigType *ty, ResolveStatus status) {
 }
 
 bool ir_get_var_is_comptime(ZigVar *var) {
-    if (!var->is_comptime)
+    // The is_comptime field can be left null, which means not comptime.
+    if (var->is_comptime == nullptr)
         return false;
-    if (var->is_comptime->other)
-        return var->is_comptime->other->value.data.x_bool;
+    // When the is_comptime field references an instruction that has to get analyzed, this
+    // is the value.
+    if (var->is_comptime->child != nullptr) {
+        assert(var->is_comptime->child->value.type->id == ZigTypeIdBool);
+        return var->is_comptime->child->value.data.x_bool;
+    }
+    // As an optimization, is_comptime values which are constant are allowed
+    // to be omitted from analysis. In this case, there is no child instruction
+    // and we simply look at the unanalyzed const parent instruction.
+    assert(var->is_comptime->value.type->id == ZigTypeIdBool);
     return var->is_comptime->value.data.x_bool;
 }
 

src/codegen.cpp

@@ -7279,10 +7279,15 @@ static void init(CodeGen *g) {
 
     define_builtin_types(g);
 
-    g->invalid_instruction = allocate<IrInstruction>(1);
+    IrInstruction *sentinel_instructions = allocate<IrInstruction>(2);
+    g->invalid_instruction = &sentinel_instructions[0];
     g->invalid_instruction->value.type = g->builtin_types.entry_invalid;
     g->invalid_instruction->value.global_refs = allocate<ConstGlobalRefs>(1);
 
+    g->unreach_instruction = &sentinel_instructions[1];
+    g->unreach_instruction->value.type = g->builtin_types.entry_unreachable;
+    g->unreach_instruction->value.global_refs = allocate<ConstGlobalRefs>(1);
+
     g->const_void_val.special = ConstValSpecialStatic;
     g->const_void_val.type = g->builtin_types.entry_void;
     g->const_void_val.global_refs = allocate<ConstGlobalRefs>(1);