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stage2: LLVM backend: memset to 0xaa for undefined stores

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Also support `one` and `int_big_positive` tags for const pointers.
This commit is contained in:
Andrew Kelley 2021-11-16 17:46:39 -07:00
parent 68fe391de0
commit 09588c795c
5 changed files with 52 additions and 11 deletions
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8
src/codegen/c.zig
View file

@ -279,7 +279,7 @@ pub const DeclGen = struct {
ty: Type,
val: Value,
) error{ OutOfMemory, AnalysisFail }!void {
if (val.isUndef()) {
if (val.isUndefDeep()) {
switch (ty.zigTypeTag()) {
// Using '{}' for integer and floats seemed to error C compilers (both GCC and Clang)
// with 'error: expected expression' (including when built with 'zig cc')
@ -1049,7 +1049,7 @@ pub fn genDecl(o: *Object) !void {
}
try fwd_decl_writer.writeAll(";\n");
if (variable.init.isUndef()) {
if (variable.init.isUndefDeep()) {
return;
}
@ -1602,8 +1602,10 @@ fn airStore(f: *Function, inst: Air.Inst.Index) !CValue {
const src_val = try f.resolveInst(bin_op.rhs);
const lhs_type = f.air.typeOf(bin_op.lhs);
// TODO Sema should emit a different instruction when the store should
// possibly do the safety 0xaa bytes for undefined.
const src_val_is_undefined =
if (f.air.value(bin_op.rhs)) |v| v.isUndef() else false;
if (f.air.value(bin_op.rhs)) |v| v.isUndefDeep() else false;
if (src_val_is_undefined)
return try airStoreUndefined(f, dest_ptr, lhs_type);

30
src/codegen/llvm.zig
View file

@ -1078,7 +1078,7 @@ pub const DeclGen = struct {
};
return self.context.constStruct(&fields, fields.len, .False);
},
.int_u64 => {
.int_u64, .one, .int_big_positive => {
const llvm_usize = try self.llvmType(Type.usize);
const llvm_int = llvm_usize.constInt(tv.val.toUnsignedInt(), .False);
return llvm_int.constIntToPtr(try self.llvmType(tv.ty));
@ -3464,8 +3464,30 @@ pub const FuncGen = struct {
const bin_op = self.air.instructions.items(.data)[inst].bin_op;
const dest_ptr = try self.resolveInst(bin_op.lhs);
const ptr_ty = self.air.typeOf(bin_op.lhs);
const src_operand = try self.resolveInst(bin_op.rhs);
self.store(dest_ptr, ptr_ty, src_operand, .NotAtomic);
// TODO Sema should emit a different instruction when the store should
// possibly do the safety 0xaa bytes for undefined.
const val_is_undef = if (self.air.value(bin_op.rhs)) |val| val.isUndefDeep() else false;
if (val_is_undef) {
const elem_ty = ptr_ty.childType();
const target = self.dg.module.getTarget();
const elem_size = elem_ty.abiSize(target);
const u8_llvm_ty = self.context.intType(8);
const ptr_u8_llvm_ty = u8_llvm_ty.pointerType(0);
const dest_ptr_u8 = self.builder.buildBitCast(dest_ptr, ptr_u8_llvm_ty, "");
const fill_char = u8_llvm_ty.constInt(0xaa, .False);
const dest_ptr_align = ptr_ty.ptrAlignment(target);
const usize_llvm_ty = try self.dg.llvmType(Type.usize);
const len = usize_llvm_ty.constInt(elem_size, .False);
_ = self.builder.buildMemSet(dest_ptr_u8, fill_char, len, dest_ptr_align, ptr_ty.isVolatilePtr());
if (self.dg.module.comp.bin_file.options.valgrind) {
// TODO generate valgrind client request to mark byte range as undefined
// see gen_valgrind_undef() in codegen.cpp
}
} else {
const src_operand = try self.resolveInst(bin_op.rhs);
self.store(dest_ptr, ptr_ty, src_operand, .NotAtomic);
}
return null;
}
@ -3651,7 +3673,7 @@ pub const FuncGen = struct {
const dest_ptr = try self.resolveInst(pl_op.operand);
const ptr_ty = self.air.typeOf(pl_op.operand);
const value = try self.resolveInst(extra.lhs);
const val_is_undef = if (self.air.value(extra.lhs)) |val| val.isUndef() else false;
const val_is_undef = if (self.air.value(extra.lhs)) |val| val.isUndefDeep() else false;
const len = try self.resolveInst(extra.rhs);
const u8_llvm_ty = self.context.intType(8);
const ptr_u8_llvm_ty = u8_llvm_ty.pointerType(0);

7
src/value.zig
View file

@ -1802,6 +1802,13 @@ pub const Value = extern union {
return self.tag() == .undef;
}
/// TODO: check for cases such as array that is not marked undef but all the element
/// values are marked undef, or struct that is not marked undef but all fields are marked
/// undef, etc.
pub fn isUndefDeep(self: Value) bool {
return self.isUndef();
}
/// Asserts the value is not undefined and not unreachable.
/// Integer value 0 is considered null because of C pointers.
pub fn isNull(self: Value) bool {

9
test/behavior/cast.zig
View file

@ -251,8 +251,13 @@ test "*const ?[*]const T to [*c]const [*c]const T" {
test "array coersion to undefined at runtime" {
@setRuntimeSafety(true);
// setRuntimeSafety isn't recognized on stage2
if (@import("builtin").zig_is_stage2 and @import("builtin").mode != .Debug and @import("builtin").mode != .ReleaseSafe) return error.SkipZigTest;
// TODO implement @setRuntimeSafety in stage2
if (@import("builtin").zig_is_stage2 and
@import("builtin").mode != .Debug and
@import("builtin").mode != .ReleaseSafe)
{
return error.SkipZigTest;
}
var array = [4]u8{ 3, 4, 5, 6 };
var undefined_val = [4]u8{ 0xAA, 0xAA, 0xAA, 0xAA };

9
test/behavior/int128.zig
View file

@ -20,8 +20,13 @@ test "uint128" {
test "undefined 128 bit int" {
@setRuntimeSafety(true);
// setRuntimeSafety isn't recognized on stage2
if (@import("builtin").zig_is_stage2 and @import("builtin").mode != .Debug and @import("builtin").mode != .ReleaseSafe) return error.SkipZigTest;
// TODO implement @setRuntimeSafety in stage2
if (@import("builtin").zig_is_stage2 and
@import("builtin").mode != .Debug and
@import("builtin").mode != .ReleaseSafe)
{
return error.SkipZigTest;
}
var undef: u128 = undefined;
var undef_signed: i128 = undefined;