stage1: small mem usage improvement for IR

move a boolean field to be represented implicitly with the enum tag.
Just borrowing one of the many strategies of stage2.

This simple change took the peak mem usage from std lib tests on
my machine from 8.21 GiB to 8.11 GiB.

3 files changed, 40 insertions, 20 deletions

diff --git a/src/stage1/all_types.hpp b/src/stage1/all_types.hpp
index 7ad585a524..5e1d4969db 100644
--- a/src/stage1/all_types.hpp
+++ b/src/stage1/all_types.hpp
@@ -2629,7 +2629,8 @@ enum IrInstSrcId {
     IrInstSrcIdResolveResult,
     IrInstSrcIdResetResult,
     IrInstSrcIdSetAlignStack,
-    IrInstSrcIdArgType,
+    IrInstSrcIdArgTypeAllowVarFalse,
+    IrInstSrcIdArgTypeAllowVarTrue,
     IrInstSrcIdExport,
     IrInstSrcIdExtern,
     IrInstSrcIdErrorReturnTrace,
@@ -4144,7 +4145,6 @@ struct IrInstSrcArgType {
 
     IrInstSrc *fn_type;
     IrInstSrc *arg_index;
-    bool allow_var;
 };
 
 struct IrInstSrcExport {
diff --git a/src/stage1/ir.cpp b/src/stage1/ir.cpp
index 7906df3b0d..c004e49e48 100644
--- a/src/stage1/ir.cpp
+++ b/src/stage1/ir.cpp
@@ -514,7 +514,8 @@ static void destroy_instruction_src(IrInstSrc *inst) {
             return heap::c_allocator.destroy(reinterpret_cast<IrInstSrcResetResult *>(inst));
         case IrInstSrcIdSetAlignStack:
             return heap::c_allocator.destroy(reinterpret_cast<IrInstSrcSetAlignStack *>(inst));
-        case IrInstSrcIdArgType:
+        case IrInstSrcIdArgTypeAllowVarFalse:
+        case IrInstSrcIdArgTypeAllowVarTrue:
             return heap::c_allocator.destroy(reinterpret_cast<IrInstSrcArgType *>(inst));
         case IrInstSrcIdExport:
             return heap::c_allocator.destroy(reinterpret_cast<IrInstSrcExport *>(inst));
@@ -1546,10 +1547,6 @@ static constexpr IrInstSrcId ir_inst_id(IrInstSrcSetAlignStack *) {
     return IrInstSrcIdSetAlignStack;
 }
 
-static constexpr IrInstSrcId ir_inst_id(IrInstSrcArgType *) {
-    return IrInstSrcIdArgType;
-}
-
 static constexpr IrInstSrcId ir_inst_id(IrInstSrcExport *) {
     return IrInstSrcIdExport;
 }
@@ -4590,10 +4587,17 @@ static IrInstSrc *ir_build_set_align_stack(IrBuilderSrc *irb, Scope *scope, AstN
 static IrInstSrc *ir_build_arg_type(IrBuilderSrc *irb, Scope *scope, AstNode *source_node,
         IrInstSrc *fn_type, IrInstSrc *arg_index, bool allow_var)
 {
-    IrInstSrcArgType *instruction = ir_build_instruction<IrInstSrcArgType>(irb, scope, source_node);
+    IrInstSrcArgType *instruction = heap::c_allocator.create<IrInstSrcArgType>();
+    instruction->base.id = allow_var ?
+        IrInstSrcIdArgTypeAllowVarTrue : IrInstSrcIdArgTypeAllowVarFalse;
+    instruction->base.base.scope = scope;
+    instruction->base.base.source_node = source_node;
+    instruction->base.base.debug_id = exec_next_debug_id(irb->exec);
+    instruction->base.owner_bb = irb->current_basic_block;
+    ir_instruction_append(irb->current_basic_block, &instruction->base);
+
     instruction->fn_type = fn_type;
     instruction->arg_index = arg_index;
-    instruction->allow_var = allow_var;
 
     ir_ref_instruction(fn_type, irb->current_basic_block);
     ir_ref_instruction(arg_index, irb->current_basic_block);
@@ -30976,7 +30980,9 @@ static IrInstGen *ir_analyze_instruction_set_align_stack(IrAnalyze *ira, IrInstS
     return ir_const_void(ira, &instruction->base.base);
 }
 
-static IrInstGen *ir_analyze_instruction_arg_type(IrAnalyze *ira, IrInstSrcArgType *instruction) {
+static IrInstGen *ir_analyze_instruction_arg_type(IrAnalyze *ira, IrInstSrcArgType *instruction,
+        bool allow_var)
+{
     IrInstGen *fn_type_inst = instruction->fn_type->child;
     ZigType *fn_type = ir_resolve_type(ira, fn_type_inst);
     if (type_is_invalid(fn_type))
@@ -30998,7 +31004,7 @@ static IrInstGen *ir_analyze_instruction_arg_type(IrAnalyze *ira, IrInstSrcArgTy
 
     FnTypeId *fn_type_id = &fn_type->data.fn.fn_type_id;
     if (arg_index >= fn_type_id->param_count) {
-        if (instruction->allow_var) {
+        if (allow_var) {
             // TODO remove this with var args
             return ir_const_type(ira, &instruction->base.base, ira->codegen->builtin_types.entry_anytype);
         }
@@ -31013,7 +31019,7 @@ static IrInstGen *ir_analyze_instruction_arg_type(IrAnalyze *ira, IrInstSrcArgTy
         // Args are only unresolved if our function is generic.
         ir_assert(fn_type->data.fn.is_generic, &instruction->base.base);
 
-        if (instruction->allow_var) {
+        if (allow_var) {
             return ir_const_type(ira, &instruction->base.base, ira->codegen->builtin_types.entry_anytype);
         } else {
             ir_add_error(ira, &arg_index_inst->base,
@@ -32383,8 +32389,10 @@ static IrInstGen *ir_analyze_instruction_base(IrAnalyze *ira, IrInstSrc *instruc
             return ir_analyze_instruction_reset_result(ira, (IrInstSrcResetResult *)instruction);
         case IrInstSrcIdSetAlignStack:
             return ir_analyze_instruction_set_align_stack(ira, (IrInstSrcSetAlignStack *)instruction);
-        case IrInstSrcIdArgType:
-            return ir_analyze_instruction_arg_type(ira, (IrInstSrcArgType *)instruction);
+        case IrInstSrcIdArgTypeAllowVarFalse:
+            return ir_analyze_instruction_arg_type(ira, (IrInstSrcArgType *)instruction, false);
+        case IrInstSrcIdArgTypeAllowVarTrue:
+            return ir_analyze_instruction_arg_type(ira, (IrInstSrcArgType *)instruction, true);
         case IrInstSrcIdExport:
             return ir_analyze_instruction_export(ira, (IrInstSrcExport *)instruction);
         case IrInstSrcIdExtern:
@@ -32826,7 +32834,8 @@ bool ir_inst_src_has_side_effects(IrInstSrc *instruction) {
         case IrInstSrcIdAlignCast:
         case IrInstSrcIdImplicitCast:
         case IrInstSrcIdResolveResult:
-        case IrInstSrcIdArgType:
+        case IrInstSrcIdArgTypeAllowVarFalse:
+        case IrInstSrcIdArgTypeAllowVarTrue:
         case IrInstSrcIdErrorReturnTrace:
         case IrInstSrcIdErrorUnion:
         case IrInstSrcIdFloatOp:
diff --git a/src/stage1/ir_print.cpp b/src/stage1/ir_print.cpp
index 98d349012e..6750b6178c 100644
--- a/src/stage1/ir_print.cpp
+++ b/src/stage1/ir_print.cpp
@@ -308,8 +308,10 @@ const char* ir_inst_src_type_str(IrInstSrcId id) {
             return "SrcResetResult";
         case IrInstSrcIdSetAlignStack:
             return "SrcSetAlignStack";
-        case IrInstSrcIdArgType:
-            return "SrcArgType";
+        case IrInstSrcIdArgTypeAllowVarFalse:
+            return "SrcArgTypeAllowVarFalse";
+        case IrInstSrcIdArgTypeAllowVarTrue:
+            return "SrcArgTypeAllowVarTrue";
         case IrInstSrcIdExport:
             return "SrcExport";
         case IrInstSrcIdExtern:
@@ -2344,11 +2346,17 @@ static void ir_print_set_align_stack(IrPrintSrc *irp, IrInstSrcSetAlignStack *in
     fprintf(irp->f, ")");
 }
 
-static void ir_print_arg_type(IrPrintSrc *irp, IrInstSrcArgType *instruction) {
+static void ir_print_arg_type(IrPrintSrc *irp, IrInstSrcArgType *instruction, bool allow_var) {
     fprintf(irp->f, "@ArgType(");
     ir_print_other_inst_src(irp, instruction->fn_type);
     fprintf(irp->f, ",");
     ir_print_other_inst_src(irp, instruction->arg_index);
+    fprintf(irp->f, ",");
+    if (allow_var) {
+        fprintf(irp->f, "allow_var=true");
+    } else {
+        fprintf(irp->f, "allow_var=false");
+    }
     fprintf(irp->f, ")");
 }
 
@@ -2942,8 +2950,11 @@ static void ir_print_inst_src(IrPrintSrc *irp, IrInstSrc *instruction, bool trai
         case IrInstSrcIdSetAlignStack:
             ir_print_set_align_stack(irp, (IrInstSrcSetAlignStack *)instruction);
             break;
-        case IrInstSrcIdArgType:
-            ir_print_arg_type(irp, (IrInstSrcArgType *)instruction);
+        case IrInstSrcIdArgTypeAllowVarFalse:
+            ir_print_arg_type(irp, (IrInstSrcArgType *)instruction, false);
+            break;
+        case IrInstSrcIdArgTypeAllowVarTrue:
+            ir_print_arg_type(irp, (IrInstSrcArgType *)instruction, true);
             break;
         case IrInstSrcIdExport:
             ir_print_export(irp, (IrInstSrcExport *)instruction);