stage2: implimentation of @setEvalBranchQuota

src/Module.zig

@@ -765,6 +765,8 @@ pub const Scope = struct {
  label: ?Label = null,
  inlining: ?*Inlining,
  is_comptime: bool,
+ /// Shared to sub-blocks.
+ branch_quota: *u32,
 
  pub const InstTable = std.AutoHashMap(*zir.Inst, *Inst);
 
@@ -792,8 +794,7 @@ pub const Scope = struct {
 
  pub const Shared = struct {
  caller: ?*Fn,
- branch_count: u64,
- branch_quota: u64,
+ branch_count: u32,
  };
  };
 
@@ -1104,6 +1105,8 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
  var inst_table = Scope.Block.InstTable.init(self.gpa);
  defer inst_table.deinit();
 
+ var branch_quota: u32 = 1000;
+
  var block_scope: Scope.Block = .{
  .parent = null,
  .inst_table = &inst_table,
@@ -1113,6 +1116,7 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
  .arena = &decl_arena.allocator,
  .inlining = null,
  .is_comptime = false,
+ .branch_quota = &branch_quota,
  };
  defer block_scope.instructions.deinit(self.gpa);
 
@@ -1297,6 +1301,8 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
  var decl_inst_table = Scope.Block.InstTable.init(self.gpa);
  defer decl_inst_table.deinit();
 
+ var branch_quota: u32 = 1000;
+
  var block_scope: Scope.Block = .{
  .parent = null,
  .inst_table = &decl_inst_table,
@@ -1306,6 +1312,7 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
  .arena = &decl_arena.allocator,
  .inlining = null,
  .is_comptime = true,
+ .branch_quota = &branch_quota,
  };
  defer block_scope.instructions.deinit(self.gpa);
 
@@ -1367,6 +1374,7 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
  var var_inst_table = Scope.Block.InstTable.init(self.gpa);
  defer var_inst_table.deinit();
 
+ var branch_quota_vi: u32 = 1000;
  var inner_block: Scope.Block = .{
  .parent = null,
  .inst_table = &var_inst_table,
@@ -1376,6 +1384,7 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
  .arena = &gen_scope_arena.allocator,
  .inlining = null,
  .is_comptime = true,
+ .branch_quota = &branch_quota_vi,
  };
  defer inner_block.instructions.deinit(self.gpa);
  try zir_sema.analyzeBody(self, &inner_block, .{
@@ -1494,6 +1503,8 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
  var inst_table = Scope.Block.InstTable.init(self.gpa);
  defer inst_table.deinit();
 
+ var branch_quota: u32 = 1000;
+
  var block_scope: Scope.Block = .{
  .parent = null,
  .inst_table = &inst_table,
@@ -1503,6 +1514,7 @@ fn astGenAndAnalyzeDecl(self: *Module, decl: *Decl) !bool {
  .arena = &analysis_arena.allocator,
  .inlining = null,
  .is_comptime = true,
+ .branch_quota = &branch_quota,
  };
  defer block_scope.instructions.deinit(self.gpa);
 
@@ -1875,6 +1887,8 @@ pub fn analyzeFnBody(self: *Module, decl: *Decl, func: *Fn) !void {
  defer decl.typed_value.most_recent.arena.?.* = arena.state;
  var inst_table = Scope.Block.InstTable.init(self.gpa);
  defer inst_table.deinit();
+ var branch_quota: u32 = 1000;
+
  var inner_block: Scope.Block = .{
  .parent = null,
  .inst_table = &inst_table,
@@ -1884,6 +1898,7 @@ pub fn analyzeFnBody(self: *Module, decl: *Decl, func: *Fn) !void {
  .arena = &arena.allocator,
  .inlining = null,
  .is_comptime = false,
+ .branch_quota = &branch_quota,
  };
  defer inner_block.instructions.deinit(self.gpa);
 
@@ -3466,7 +3481,9 @@ pub fn addSafetyCheck(mod: *Module, parent_block: *Scope.Block, ok: *Inst, panic
  .arena = parent_block.arena,
  .inlining = parent_block.inlining,
  .is_comptime = parent_block.is_comptime,
+ .branch_quota = parent_block.branch_quota,
  };
+
  defer fail_block.instructions.deinit(mod.gpa);
 
  _ = try mod.safetyPanic(&fail_block, ok.src, panic_id);
@@ -3532,10 +3549,10 @@ pub fn identifierTokenString(mod: *Module, scope: *Scope, token: ast.TokenIndex)
 pub fn emitBackwardBranch(mod: *Module, block: *Scope.Block, src: usize) !void {
  const shared = block.inlining.?.shared;
  shared.branch_count += 1;
- if (shared.branch_count > shared.branch_quota) {
+ if (shared.branch_count > block.branch_quota.*) {
  // TODO show the "called from here" stack
  return mod.fail(&block.base, src, "evaluation exceeded {d} backwards branches", .{
-shared.branch_quota,
+block.branch_quota.*,
  });
  }
 }

src/astgen.zig

@@ -2317,6 +2317,19 @@ fn compileError(mod: *Module, scope: *Scope, call: *ast.Node.BuiltinCall) InnerE
  return addZIRUnOp(mod, scope, src, .compileerror, target);
 }
 
+fn setEvalBranchQuota(mod: *Module, scope: *Scope, call: *ast.Node.BuiltinCall) InnerError!*zir.Inst {
+ try ensureBuiltinParamCount(mod, scope, call, 1);
+ const tree = scope.tree();
+ const src = tree.token_locs[call.builtin_token].start;
+ const params = call.params();
+ const target = try expr(mod, scope, .none, params[0]);
+ const u32_type = try addZIRInstConst(mod, scope, src, .{
+ .ty = Type.initTag(.type),
+ .val = Value.initTag(.u32_type),
+ });
+ return addZIRUnOp(mod, scope, src, .setevalbranchquota, try rlWrap(mod, scope, .{ .ty = u32_type }, target));
+}
+
 fn typeOf(mod: *Module, scope: *Scope, rl: ResultLoc, call: *ast.Node.BuiltinCall) InnerError!*zir.Inst {
  const tree = scope.tree();
  const arena = scope.arena();
@@ -2362,6 +2375,8 @@ fn builtinCall(mod: *Module, scope: *Scope, rl: ResultLoc, call: *ast.Node.Built
  return rlWrap(mod, scope, rl, try import(mod, scope, call));
  } else if (mem.eql(u8, builtin_name, "@compileError")) {
  return compileError(mod, scope, call);
+ } else if (mem.eql(u8, builtin_name, "@setEvalBranchQuota")) {
+ return setEvalBranchQuota(mod, scope, call);
  } else {
  return mod.failTok(scope, call.builtin_token, "invalid builtin function: '{s}'", .{builtin_name});
  }

src/zir.zig

@@ -127,6 +127,8 @@ pub const Inst = struct {
  coerce_to_ptr_elem,
  /// Emit an error message and fail compilation.
  compileerror,
+ /// Changes the maximum number of backwards branches that compile-time code execution can use before giving up and making a compile error.
+ setevalbranchquota,
  /// Conditional branch. Splits control flow based on a boolean condition value.
  condbr,
  /// Special case, has no textual representation.
@@ -347,6 +349,7 @@ pub const Inst = struct {
  .anyframe_type,
  .bitnot,
  .import,
+ .setevalbranchquota,
  => UnOp,
 
  .add,
@@ -535,6 +538,7 @@ pub const Inst = struct {
  .switch_range,
  .typeof_peer,
  .resolve_inferred_alloc,
+ .setevalbranchquota,
  => false,
 
  .@"break",

src/zir_sema.zig

@@ -81,6 +81,7 @@ pub fn analyzeInst(mod: *Module, scope: *Scope, old_inst: *zir.Inst) InnerError!
  .mut_slice_type => return analyzeInstSimplePtrType(mod, scope, old_inst.castTag(.mut_slice_type).?, true, .Slice),
  .ptr_type => return analyzeInstPtrType(mod, scope, old_inst.castTag(.ptr_type).?),
  .store => return analyzeInstStore(mod, scope, old_inst.castTag(.store).?),
+ .setevalbranchquota => return analyzeInstSetEvalBranchQuota(mod, scope, old_inst.castTag(.setevalbranchquota).?),
  .str => return analyzeInstStr(mod, scope, old_inst.castTag(.str).?),
  .int => {
  const big_int = old_inst.castTag(.int).?.positionals.int;
@@ -486,6 +487,18 @@ fn analyzeInstStoreToInferredPtr(
  return mod.storePtr(scope, inst.base.src, bitcasted_ptr, value);
 }
 
+fn analyzeInstSetEvalBranchQuota(
+ mod: *Module,
+ scope: *Scope,
+ inst: *zir.Inst.UnOp,
+) InnerError!*Inst {
+ const b = try mod.requireFunctionBlock(scope, inst.base.src);
+ const quota = @truncate(u32, try resolveInt(mod, scope, inst.positionals.operand, Type.initTag(.u32)));
+ if (b.branch_quota.* < quota)
+ b.branch_quota.* = quota;
+ return mod.constVoid(scope, inst.base.src);
+}
+
 fn analyzeInstStore(mod: *Module, scope: *Scope, inst: *zir.Inst.BinOp) InnerError!*Inst {
  const ptr = try resolveInst(mod, scope, inst.positionals.lhs);
  const value = try resolveInst(mod, scope, inst.positionals.rhs);
@@ -594,6 +607,7 @@ fn analyzeInstLoop(mod: *Module, scope: *Scope, inst: *zir.Inst.Loop) InnerError
  .arena = parent_block.arena,
  .inlining = parent_block.inlining,
  .is_comptime = parent_block.is_comptime,
+ .branch_quota = parent_block.branch_quota,
  };
  defer child_block.instructions.deinit(mod.gpa);
 
@@ -619,6 +633,7 @@ fn analyzeInstBlockFlat(mod: *Module, scope: *Scope, inst: *zir.Inst.Block, is_c
  .label = null,
  .inlining = parent_block.inlining,
  .is_comptime = parent_block.is_comptime or is_comptime,
+ .branch_quota = parent_block.branch_quota,
  };
  defer child_block.instructions.deinit(mod.gpa);
 
@@ -666,6 +681,7 @@ fn analyzeInstBlock(mod: *Module, scope: *Scope, inst: *zir.Inst.Block, is_compt
  }),
  .inlining = parent_block.inlining,
  .is_comptime = is_comptime or parent_block.is_comptime,
+ .branch_quota = parent_block.branch_quota,
  };
  const merges = &child_block.label.?.merges;
 
@@ -867,7 +883,6 @@ fn analyzeInstCall(mod: *Module, scope: *Scope, inst: *zir.Inst.Call) InnerError
  // Otherwise we pass on the shared data from the parent scope.
  var shared_inlining = Scope.Block.Inlining.Shared{
  .branch_count = 0,
- .branch_quota = 1000,
  .caller = b.func,
  };
  // This one is shared among sub-blocks within the same callee, but not
@@ -896,7 +911,9 @@ fn analyzeInstCall(mod: *Module, scope: *Scope, inst: *zir.Inst.Call) InnerError
  .label = null,
  .inlining = &inlining,
  .is_comptime = is_comptime_call,
+ .branch_quota = b.branch_quota,
  };
+
  const merges = &child_block.inlining.?.merges;
 
  defer child_block.instructions.deinit(mod.gpa);
@@ -1417,6 +1434,7 @@ fn analyzeInstSwitchBr(mod: *Module, scope: *Scope, inst: *zir.Inst.SwitchBr) In
  .arena = parent_block.arena,
  .inlining = parent_block.inlining,
  .is_comptime = parent_block.is_comptime,
+ .branch_quota = parent_block.branch_quota,
  };
  defer case_block.instructions.deinit(mod.gpa);
 
@@ -1960,6 +1978,7 @@ fn analyzeInstCondBr(mod: *Module, scope: *Scope, inst: *zir.Inst.CondBr) InnerE
  .arena = parent_block.arena,
  .inlining = parent_block.inlining,
  .is_comptime = parent_block.is_comptime,
+ .branch_quota = parent_block.branch_quota,
  };
  defer true_block.instructions.deinit(mod.gpa);
  try analyzeBody(mod, &true_block, inst.positionals.then_body);
@@ -1973,6 +1992,7 @@ fn analyzeInstCondBr(mod: *Module, scope: *Scope, inst: *zir.Inst.CondBr) InnerE
  .arena = parent_block.arena,
  .inlining = parent_block.inlining,
  .is_comptime = parent_block.is_comptime,
+ .branch_quota = parent_block.branch_quota,
  };
  defer false_block.instructions.deinit(mod.gpa);
  try analyzeBody(mod, &false_block, inst.positionals.else_body);

test/stage2/cbe.zig

@@ -67,7 +67,22 @@ pub fn addCases(ctx: *TestContext) !void {
  \\}
  , "");
  }
+ {
+ var case = ctx.exeFromCompiledC("@setEvalBranchQuota", .{});
 
+ case.addCompareOutput(
+ \\export fn main() i32 {
+ \\ @setEvalBranchQuota(1001);
+ \\ const y = rec(1001);
+ \\ return y - 1;
+ \\}
+ \\
+ \\inline fn rec(n: usize) usize {
+ \\ if (n <= 1) return n;
+ \\ return rec(n - 1);
+ \\}
+ , "");
+ }
  ctx.c("empty start function", linux_x64,
  \\export fn _start() noreturn {
  \\ unreachable;