authorgravatar for andrew@ziglang.orgAndrew Kelley <andrew@ziglang.org> 2022-03-27 15:24:39-04:00
committergravatar for noreply@github.comGitHub <noreply@github.com> 2022-03-27 15:24:39-04:00
log0501962b4c01ee511aa0ae4b41cca4af7209bd8e
tree15a60984f65d9cbbb748c5ee64ba0d966d804225
parentd15bbebe2e6b8fcbfcd730a6c0d1be621b27045d
parente1bb09648fbd827975b9f589fa849aabefe73f67
signaturebadge-question-mark Signed by PGP key 4AEE18F83AFDEB23

Merge pull request #11321 from Luukdegram/wasm-overflow

stage2: wasm - Implement overflow arithmetic

2 files changed, 156 insertions(+), 32 deletions(-)

src/arch/wasm/CodeGen.zig+156-25
......@@ -1303,10 +1303,16 @@ fn genInst(self: *Self, inst: Air.Inst.Index) !WValue {
13031303 .bool_and => self.airBinOp(inst, .@"and"),
13041304 .bool_or => self.airBinOp(inst, .@"or"),
13051305 .rem => self.airBinOp(inst, .rem),
1306 .shl, .shl_exact => self.airBinOp(inst, .shl),
1306 .shl => self.airWrapBinOp(inst, .shl),
1307 .shl_exact => self.airBinOp(inst, .shl),
13071308 .shr, .shr_exact => self.airBinOp(inst, .shr),
13081309 .xor => self.airBinOp(inst, .xor),
13091310
1311 .add_with_overflow => self.airBinOpOverflow(inst, .add),
1312 .sub_with_overflow => self.airBinOpOverflow(inst, .sub),
1313 .shl_with_overflow => self.airBinOpOverflow(inst, .shl),
1314 .mul_with_overflow => self.airBinOpOverflow(inst, .mul),
1315
13101316 .cmp_eq => self.airCmp(inst, .eq),
13111317 .cmp_gte => self.airCmp(inst, .gte),
13121318 .cmp_gt => self.airCmp(inst, .gt),
......@@ -1461,13 +1467,6 @@ fn genInst(self: *Self, inst: Air.Inst.Index) !WValue {
14611467 .atomic_rmw,
14621468 .tag_name,
14631469 .mul_add,
1464
1465 // For these 4, probably best to wait until https://github.com/ziglang/zig/issues/10248
1466 // is implemented in the frontend before implementing them here in the wasm backend.
1467 .add_with_overflow,
1468 .sub_with_overflow,
1469 .mul_with_overflow,
1470 .shl_with_overflow,
14711470 => |tag| return self.fail("TODO: Implement wasm inst: {s}", .{@tagName(tag)}),
14721471 };
14731472}
......@@ -1754,24 +1753,28 @@ fn airBinOp(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
17541753 const lhs = try self.resolveInst(bin_op.lhs);
17551754 const rhs = try self.resolveInst(bin_op.rhs);
17561755 const operand_ty = self.air.typeOfIndex(inst);
1756 const ty = self.air.typeOf(bin_op.lhs);
17571757
17581758 if (isByRef(operand_ty, self.target)) {
17591759 return self.fail("TODO: Implement binary operation for type: {}", .{operand_ty.fmtDebug()});
17601760 }
17611761
1762 return self.binOp(lhs, rhs, ty, op);
1763}
1764
1765fn binOp(self: *Self, lhs: WValue, rhs: WValue, ty: Type, op: Op) InnerError!WValue {
17621766 try self.emitWValue(lhs);
17631767 try self.emitWValue(rhs);
17641768
1765 const bin_ty = self.air.typeOf(bin_op.lhs);
17661769 const opcode: wasm.Opcode = buildOpcode(.{
17671770 .op = op,
1768 .valtype1 = typeToValtype(bin_ty, self.target),
1769 .signedness = if (bin_ty.isSignedInt()) .signed else .unsigned,
1771 .valtype1 = typeToValtype(ty, self.target),
1772 .signedness = if (ty.isSignedInt()) .signed else .unsigned,
17701773 });
17711774 try self.addTag(Mir.Inst.Tag.fromOpcode(opcode));
17721775
17731776 // save the result in a temporary
1774 const bin_local = try self.allocLocal(bin_ty);
1777 const bin_local = try self.allocLocal(ty);
17751778 try self.addLabel(.local_set, bin_local.local);
17761779 return bin_local;
17771780}
......@@ -1781,18 +1784,21 @@ fn airWrapBinOp(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
17811784 const lhs = try self.resolveInst(bin_op.lhs);
17821785 const rhs = try self.resolveInst(bin_op.rhs);
17831786
1787 return self.wrapBinOp(lhs, rhs, self.air.typeOf(bin_op.lhs), op);
1788}
1789
1790fn wrapBinOp(self: *Self, lhs: WValue, rhs: WValue, ty: Type, op: Op) InnerError!WValue {
17841791 try self.emitWValue(lhs);
17851792 try self.emitWValue(rhs);
17861793
1787 const bin_ty = self.air.typeOf(bin_op.lhs);
17881794 const opcode: wasm.Opcode = buildOpcode(.{
17891795 .op = op,
1790 .valtype1 = typeToValtype(bin_ty, self.target),
1791 .signedness = if (bin_ty.isSignedInt()) .signed else .unsigned,
1796 .valtype1 = typeToValtype(ty, self.target),
1797 .signedness = if (ty.isSignedInt()) .signed else .unsigned,
17921798 });
17931799 try self.addTag(Mir.Inst.Tag.fromOpcode(opcode));
17941800
1795 const int_info = bin_ty.intInfo(self.target);
1801 const int_info = ty.intInfo(self.target);
17961802 const bitsize = int_info.bits;
17971803 const is_signed = int_info.signedness == .signed;
17981804 // if target type bitsize is x < 32 and 32 > x < 64, we perform
......@@ -1820,7 +1826,7 @@ fn airWrapBinOp(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
18201826 }
18211827
18221828 // save the result in a temporary
1823 const bin_local = try self.allocLocal(bin_ty);
1829 const bin_local = try self.allocLocal(ty);
18241830 try self.addLabel(.local_set, bin_local.local);
18251831 return bin_local;
18261832}
......@@ -2202,18 +2208,21 @@ fn airCmp(self: *Self, inst: Air.Inst.Index, op: std.math.CompareOperator) Inner
22022208 const lhs = try self.resolveInst(bin_op.lhs);
22032209 const rhs = try self.resolveInst(bin_op.rhs);
22042210 const operand_ty = self.air.typeOf(bin_op.lhs);
2211 return self.cmp(lhs, rhs, operand_ty, op);
2212}
22052213
2206 if (operand_ty.zigTypeTag() == .Optional and !operand_ty.isPtrLikeOptional()) {
2214fn cmp(self: *Self, lhs: WValue, rhs: WValue, ty: Type, op: std.math.CompareOperator) InnerError!WValue {
2215 if (ty.zigTypeTag() == .Optional and !ty.isPtrLikeOptional()) {
22072216 var buf: Type.Payload.ElemType = undefined;
2208 const payload_ty = operand_ty.optionalChild(&buf);
2217 const payload_ty = ty.optionalChild(&buf);
22092218 if (payload_ty.hasRuntimeBitsIgnoreComptime()) {
22102219 // When we hit this case, we must check the value of optionals
22112220 // that are not pointers. This means first checking against non-null for
22122221 // both lhs and rhs, as well as checking the payload are matching of lhs and rhs
2213 return self.cmpOptionals(lhs, rhs, operand_ty, op);
2222 return self.cmpOptionals(lhs, rhs, ty, op);
22142223 }
2215 } else if (isByRef(operand_ty, self.target)) {
2216 return self.cmpBigInt(lhs, rhs, operand_ty, op);
2224 } else if (isByRef(ty, self.target)) {
2225 return self.cmpBigInt(lhs, rhs, ty, op);
22172226 }
22182227
22192228 // ensure that when we compare pointers, we emit
......@@ -2229,13 +2238,13 @@ fn airCmp(self: *Self, inst: Air.Inst.Index, op: std.math.CompareOperator) Inner
22292238
22302239 const signedness: std.builtin.Signedness = blk: {
22312240 // by default we tell the operand type is unsigned (i.e. bools and enum values)
2232 if (operand_ty.zigTypeTag() != .Int) break :blk .unsigned;
2241 if (ty.zigTypeTag() != .Int) break :blk .unsigned;
22332242
22342243 // incase of an actual integer, we emit the correct signedness
2235 break :blk operand_ty.intInfo(self.target).signedness;
2244 break :blk ty.intInfo(self.target).signedness;
22362245 };
22372246 const opcode: wasm.Opcode = buildOpcode(.{
2238 .valtype1 = typeToValtype(operand_ty, self.target),
2247 .valtype1 = typeToValtype(ty, self.target),
22392248 .op = switch (op) {
22402249 .lt => .lt,
22412250 .lte => .le,
......@@ -3730,3 +3739,125 @@ fn airPtrSliceFieldPtr(self: *Self, inst: Air.Inst.Index, offset: u32) InnerErro
37303739 const slice_ptr = try self.resolveInst(ty_op.operand);
37313740 return self.buildPointerOffset(slice_ptr, offset, .new);
37323741}
3742
3743fn airBinOpOverflow(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
3744 if (self.liveness.isUnused(inst)) return WValue{ .none = {} };
3745
3746 const ty_pl = self.air.instructions.items(.data)[inst].ty_pl;
3747 const extra = self.air.extraData(Air.Bin, ty_pl.payload).data;
3748 const lhs = try self.resolveInst(extra.lhs);
3749 const rhs = try self.resolveInst(extra.rhs);
3750 const lhs_ty = self.air.typeOf(extra.lhs);
3751
3752 // We store the bit if it's overflowed or not in this. As it's zero-initialized
3753 // we only need to update it if an overflow (or underflow) occured.
3754 const overflow_bit = try self.allocLocal(Type.initTag(.u1));
3755 const int_info = lhs_ty.intInfo(self.target);
3756 const wasm_bits = toWasmBits(int_info.bits) orelse {
3757 return self.fail("TODO: Implement overflow arithmetic for integer bitsize: {d}", .{int_info.bits});
3758 };
3759
3760 const zero = switch (wasm_bits) {
3761 32 => WValue{ .imm32 = 0 },
3762 64 => WValue{ .imm64 = 0 },
3763 else => unreachable,
3764 };
3765 const int_max = (@as(u65, 1) << @intCast(u7, int_info.bits - @boolToInt(int_info.signedness == .signed))) - 1;
3766 const int_max_wvalue = switch (wasm_bits) {
3767 32 => WValue{ .imm32 = @intCast(u32, int_max) },
3768 64 => WValue{ .imm64 = @intCast(u64, int_max) },
3769 else => unreachable,
3770 };
3771 const int_min = if (int_info.signedness == .unsigned)
3772 @as(i64, 0)
3773 else
3774 -@as(i64, 1) << @intCast(u6, int_info.bits - 1);
3775 const int_min_wvalue = switch (wasm_bits) {
3776 32 => WValue{ .imm32 = @bitCast(u32, @intCast(i32, int_min)) },
3777 64 => WValue{ .imm64 = @bitCast(u64, int_min) },
3778 else => unreachable,
3779 };
3780
3781 if (int_info.signedness == .unsigned and op == .add) {
3782 const diff = try self.binOp(int_max_wvalue, lhs, lhs_ty, .sub);
3783 const cmp_res = try self.cmp(rhs, diff, lhs_ty, .gt);
3784 try self.emitWValue(cmp_res);
3785 try self.addLabel(.local_set, overflow_bit.local);
3786 } else if (int_info.signedness == .unsigned and op == .sub) {
3787 const cmp_res = try self.cmp(lhs, rhs, lhs_ty, .lt);
3788 try self.emitWValue(cmp_res);
3789 try self.addLabel(.local_set, overflow_bit.local);
3790 } else if (int_info.signedness == .signed and op != .shl) {
3791 // for overflow, we first check if lhs is > 0 (or lhs < 0 in case of subtraction). If not, we will not overflow.
3792 // We first create an outer block, where we handle overflow.
3793 // Then we create an inner block, where underflow is handled.
3794 try self.startBlock(.block, wasm.block_empty);
3795 try self.startBlock(.block, wasm.block_empty);
3796 {
3797 try self.emitWValue(lhs);
3798 const cmp_result = try self.cmp(lhs, zero, lhs_ty, .lt);
3799 try self.emitWValue(cmp_result);
3800 }
3801 try self.addLabel(.br_if, 0); // break to outer block, and handle underflow
3802
3803 // handle overflow
3804 {
3805 const diff = try self.binOp(int_max_wvalue, lhs, lhs_ty, .sub);
3806 const cmp_res = try self.cmp(rhs, diff, lhs_ty, if (op == .add) .gt else .lt);
3807 try self.emitWValue(cmp_res);
3808 try self.addLabel(.local_set, overflow_bit.local);
3809 }
3810 try self.addLabel(.br, 1); // break from blocks, and continue regular flow.
3811 try self.endBlock();
3812
3813 // handle underflow
3814 {
3815 const diff = try self.binOp(int_min_wvalue, lhs, lhs_ty, .sub);
3816 const cmp_res = try self.cmp(rhs, diff, lhs_ty, if (op == .add) .lt else .gt);
3817 try self.emitWValue(cmp_res);
3818 try self.addLabel(.local_set, overflow_bit.local);
3819 }
3820 try self.endBlock();
3821 }
3822
3823 const bin_op = if (op == .shl) blk: {
3824 const tmp_val = try self.binOp(lhs, rhs, lhs_ty, op);
3825 const cmp_res = try self.cmp(tmp_val, int_max_wvalue, lhs_ty, .gt);
3826 try self.emitWValue(cmp_res);
3827 try self.addLabel(.local_set, overflow_bit.local);
3828
3829 try self.emitWValue(tmp_val);
3830 try self.emitWValue(int_max_wvalue);
3831 switch (wasm_bits) {
3832 32 => try self.addTag(.i32_and),
3833 64 => try self.addTag(.i64_and),
3834 else => unreachable,
3835 }
3836 try self.addLabel(.local_set, tmp_val.local);
3837 break :blk tmp_val;
3838 } else if (op == .mul) blk: {
3839 const bin_op = try self.wrapBinOp(lhs, rhs, lhs_ty, op);
3840 try self.startBlock(.block, wasm.block_empty);
3841 // check if 0. true => Break out of block as cannot over -or underflow.
3842 try self.emitWValue(lhs);
3843 switch (wasm_bits) {
3844 32 => try self.addTag(.i32_eqz),
3845 64 => try self.addTag(.i64_eqz),
3846 else => unreachable,
3847 }
3848 try self.addLabel(.br_if, 0);
3849 const div = try self.binOp(bin_op, lhs, lhs_ty, .div);
3850 const cmp_res = try self.cmp(div, rhs, lhs_ty, .neq);
3851 try self.emitWValue(cmp_res);
3852 try self.addLabel(.local_set, overflow_bit.local);
3853 try self.endBlock();
3854 break :blk bin_op;
3855 } else try self.wrapBinOp(lhs, rhs, lhs_ty, op);
3856
3857 const result_ptr = try self.allocStack(self.air.typeOfIndex(inst));
3858 try self.store(result_ptr, bin_op, lhs_ty, 0);
3859 const offset = @intCast(u32, lhs_ty.abiSize(self.target));
3860 try self.store(result_ptr, overflow_bit, Type.initTag(.u1), offset);
3861
3862 return result_ptr;
3863}
test/behavior/math.zig-7
......@@ -639,7 +639,6 @@ test "128-bit multiplication" {
639639
640640test "@addWithOverflow" {
641641 if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
642 if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
643642 if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
644643 if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
645644 if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
......@@ -661,7 +660,6 @@ test "@addWithOverflow" {
661660
662661test "small int addition" {
663662 if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
664 if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
665663 if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
666664 if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
667665 if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
......@@ -686,7 +684,6 @@ test "small int addition" {
686684
687685test "@mulWithOverflow" {
688686 if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
689 if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
690687 if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
691688 if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
692689 if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
......@@ -708,7 +705,6 @@ test "@mulWithOverflow" {
708705
709706test "@subWithOverflow" {
710707 if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
711 if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
712708 if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
713709 if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
714710 if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
......@@ -730,7 +726,6 @@ test "@subWithOverflow" {
730726
731727test "@shlWithOverflow" {
732728 if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
733 if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
734729 if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
735730 if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
736731 if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
......@@ -752,7 +747,6 @@ test "@shlWithOverflow" {
752747
753748test "overflow arithmetic with u0 values" {
754749 if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
755 if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
756750 if (builtin.zig_backend == .stage2_x86_64) return error.SkipZigTest; // TODO
757751
758752 var result: u0 = undefined;
......@@ -879,7 +873,6 @@ test "quad hex float literal parsing accurate" {
879873}
880874
881875test "truncating shift left" {
882 if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
883876 if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest; // TODO
884877
885878 try testShlTrunc(maxInt(u16));