From 6c1ab376ddcdbb05610487e5b813d42ff37da40d Mon Sep 17 00:00:00 2001 From: Luuk de Gram Date: Mon, 17 Apr 2023 20:05:24 +0200 Subject: [PATCH] wasm: store `__zig_lt_errors_len` in linear data Rather than using a function call to verify if an error fits within the global error set's length, we now store the error set' size in the .rodata segment of the linear memory and load that value onto the stack to check with the integer value. --- src/arch/wasm/CodeGen.zig | 12 +++---- src/link/Wasm.zig | 76 +++++++++++++++++++-------------------- 2 files changed, 43 insertions(+), 45 deletions(-) diff --git a/src/arch/wasm/CodeGen.zig b/src/arch/wasm/CodeGen.zig index c0bab03428..9bf39b73f1 100644 --- a/src/arch/wasm/CodeGen.zig +++ b/src/arch/wasm/CodeGen.zig @@ -3339,13 +3339,14 @@ fn airCmpVector(func: *CodeGen, inst: Air.Inst.Index) InnerError!void { fn airCmpLtErrorsLen(func: *CodeGen, inst: Air.Inst.Index) InnerError!void { const un_op = func.air.instructions.items(.data)[inst].un_op; const operand = try func.resolveInst(un_op); - const sym_index = try func.bin_file.getGlobalSymbol("__zig_lt_errors_len", null); + const sym_index = try func.bin_file.getGlobalSymbol("__zig_errors_len", null); + const errors_len = WValue{ .memory = sym_index }; try func.emitWValue(operand); - try func.addLabel(.call, sym_index); - const result = try func.allocLocal(Type.bool); - try func.addLabel(.local_set, result.local.value); - return func.finishAir(inst, result, &.{un_op}); + const errors_len_val = try func.load(errors_len, Type.err_int, 0); + const result = try func.cmp(.stack, errors_len_val, Type.err_int, .lt); + + return func.finishAir(inst, try result.toLocal(func, Type.bool), &.{un_op}); } fn airBr(func: *CodeGen, inst: Air.Inst.Index) InnerError!void { @@ -6518,7 +6519,6 @@ fn getTagNameFunction(func: *CodeGen, enum_ty: Type) InnerError!u32 { fn airErrorSetHasValue(func: *CodeGen, inst: Air.Inst.Index) InnerError!void { const ty_op = func.air.instructions.items(.data)[inst].ty_op; - if (func.liveness.isUnused(inst)) return func.finishAir(inst, .none, &.{ty_op.operand}); const operand = try func.resolveInst(ty_op.operand); const error_set_ty = func.air.getRefType(ty_op.ty); diff --git a/src/link/Wasm.zig b/src/link/Wasm.zig index 1b7c43a6a0..0fe9ec5e3b 100644 --- a/src/link/Wasm.zig +++ b/src/link/Wasm.zig @@ -1209,9 +1209,10 @@ fn resolveLazySymbols(wasm: *Wasm) !void { try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc); } } - if (wasm.undefs.fetchSwapRemove("__zig_lt_errors_len")) |kv| { - const loc = try wasm.createSyntheticSymbol("__zig_lt_errors_len", .function); + if (wasm.undefs.fetchSwapRemove("__zig_errors_len")) |kv| { + const loc = try wasm.createSyntheticSymbol("__zig_errors_len", .data); try wasm.discarded.putNoClobber(wasm.base.allocator, kv.value, loc); + _ = wasm.resolved_symbols.swapRemove(kv.value); } } @@ -2189,44 +2190,41 @@ fn setupInitFunctions(wasm: *Wasm) !void { std.sort.sort(InitFuncLoc, wasm.init_funcs.items, {}, InitFuncLoc.lessThan); } -/// Generates the function which verifies if an integer value is less than the -/// amount of error values. This will only be generated if the symbol exists. -fn setupLtErrorsLenFunction(wasm: *Wasm) !void { - if (wasm.findGlobalSymbol("__zig_lt_errors_len") == null) return; +/// Generates an atom containing the global error set' size. +/// This will only be generated if the symbol exists. +fn setupErrorsLen(wasm: *Wasm) !void { + const loc = wasm.findGlobalSymbol("__zig_errors_len") orelse return; + const errors_len = wasm.base.options.module.?.global_error_set.count(); + // overwrite existing atom if it already exists (maybe the error set has increased) + // if not, allcoate a new atom. + const atom_index = if (wasm.symbol_atom.get(loc)) |index| blk: { + const atom = wasm.getAtomPtr(index); + if (atom.next) |next_atom_index| { + const next_atom = wasm.getAtomPtr(next_atom_index); + next_atom.prev = atom.prev; + atom.next = null; + } + if (atom.prev) |prev_index| { + const prev_atom = wasm.getAtomPtr(prev_index); + prev_atom.next = atom.next; + atom.prev = null; + } + atom.deinit(wasm); + break :blk index; + } else new_atom: { + const atom_index = @intCast(Atom.Index, wasm.managed_atoms.items.len); + try wasm.symbol_atom.put(wasm.base.allocator, loc, atom_index); + try wasm.managed_atoms.append(wasm.base.allocator, undefined); + break :new_atom atom_index; + }; + const atom = wasm.getAtomPtr(atom_index); + atom.* = Atom.empty; + atom.sym_index = loc.index; + atom.size = 2; + try atom.code.writer(wasm.base.allocator).writeIntLittle(u16, @intCast(u16, errors_len)); - var body_list = std.ArrayList(u8).init(wasm.base.allocator); - defer body_list.deinit(); - const writer = body_list.writer(); - - { - // generates bytecode for the following function: - // fn (index: u16) bool { - // return index < errors_len; - // } - - // no locals - try leb.writeULEB128(writer, @as(u32, 0)); - - // get argument - try writer.writeByte(std.wasm.opcode(.local_get)); - try leb.writeULEB128(writer, @as(u32, 0)); - - // get error length - try writer.writeByte(std.wasm.opcode(.i32_const)); - try leb.writeULEB128(writer, @intCast(u32, errors_len)); - - try writer.writeByte(std.wasm.opcode(.i32_lt_u)); - - // stack values are implicit return values so keep the value - // on the stack and end the function. - - // end function - try writer.writeByte(std.wasm.opcode(.end)); - } - - const func_type: std.wasm.Type = .{ .params = &.{std.wasm.Valtype.i32}, .returns = &.{std.wasm.Valtype.i32} }; - try wasm.createSyntheticFunction("__zig_lt_errors_len", func_type, &body_list); + try wasm.parseAtom(atom_index, .{ .data = .read_only }); } /// Creates a function body for the `__wasm_call_ctors` symbol. @@ -3361,6 +3359,7 @@ pub fn flushModule(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Nod // So we can rebuild the binary file on each incremental update defer wasm.resetState(); try wasm.setupInitFunctions(); + try wasm.setupErrorsLen(); try wasm.setupStart(); try wasm.setupImports(); if (wasm.base.options.module) |mod| { @@ -3423,7 +3422,6 @@ pub fn flushModule(wasm: *Wasm, comp: *Compilation, prog_node: *std.Progress.Nod try wasm.setupInitMemoryFunction(); try wasm.setupTLSRelocationsFunction(); try wasm.initializeTLSFunction(); - try wasm.setupLtErrorsLenFunction(); try wasm.setupExports(); try wasm.writeToFile(enabled_features, emit_features_count, arena); }