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wasm: implement saturating add, sub for unsigned

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Implements +| and -| for unsigned integers <= 64 bits.
This commit is contained in:
Luuk de Gram 2022-06-15 20:26:53 +02:00
parent 33cf6ef621
commit fcd4280a8c
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GPG Key ID: A8CFE58E4DC7D664
1 changed files with 63 additions and 2 deletions
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65
src/arch/wasm/CodeGen.zig
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@ -1432,8 +1432,10 @@ fn genInst(self: *Self, inst: Air.Inst.Index) !WValue {
.const_ty => unreachable,
.add => self.airBinOp(inst, .add),
.add_sat => self.airSatBinOp(inst, .add),
.addwrap => self.airWrapBinOp(inst, .add),
.sub => self.airBinOp(inst, .sub),
.sub_sat => self.airSatBinOp(inst, .sub),
.subwrap => self.airWrapBinOp(inst, .sub),
.mul => self.airBinOp(inst, .mul),
.mulwrap => self.airWrapBinOp(inst, .mul),
@ -1583,8 +1585,6 @@ fn genInst(self: *Self, inst: Air.Inst.Index) !WValue {
.memcpy => self.airMemcpy(inst),
.add_sat,
.sub_sat,
.mul_sat,
.mod,
.assembly,
@ -4878,3 +4878,64 @@ fn airCeilFloorTrunc(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValu
try self.addLabel(.local_set, result.local);
return result;
}
fn airSatBinOp(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
assert(op == .add or op == .sub);
if (self.liveness.isUnused(inst)) return WValue{ .none = {} };
const bin_op = self.air.instructions.items(.data)[inst].bin_op;
const ty = self.air.typeOfIndex(inst);
const lhs_operand = try self.resolveInst(bin_op.lhs);
const rhs_operand = try self.resolveInst(bin_op.rhs);
const int_info = ty.intInfo(self.target);
const is_signed = int_info.signedness == .signed;
if (int_info.bits > 64) {
return self.fail("TODO: saturating arithmetic for integers with bitsize '{d}'", .{int_info.bits});
}
const wasm_bits = toWasmBits(int_info.bits).?;
const lhs = if (is_signed) blk: {
break :blk try self.signAbsValue(lhs_operand, ty);
} else lhs_operand;
const rhs = if (is_signed) blk: {
break :blk try self.signAbsValue(rhs_operand, ty);
} else rhs_operand;
const opcode = buildOpcode(.{ .op = op, .valtype1 = typeToValtype(ty, self.target) });
try self.emitWValue(lhs);
try self.emitWValue(rhs);
try self.addTag(Mir.Inst.Tag.fromOpcode(opcode));
const bin_result = try self.allocLocal(ty);
try self.addLabel(.local_set, bin_result.local);
if (wasm_bits != int_info.bits and op == .add) {
const val: u64 = @intCast(u64, (@as(u65, 1) << @intCast(u7, int_info.bits)) - 1);
const imm_val = switch (wasm_bits) {
32 => WValue{ .imm32 = @intCast(u32, val) },
64 => WValue{ .imm64 = val },
else => unreachable,
};
const cmp_result = try self.cmp(bin_result, imm_val, ty, if (op == .add) .lt else .gt);
try self.emitWValue(bin_result);
try self.emitWValue(imm_val);
try self.emitWValue(cmp_result);
} else {
const cmp_result = try self.cmp(bin_result, lhs, ty, if (op == .add) .lt else .gt);
switch (wasm_bits) {
32 => try self.addImm32(if (op == .add) @as(i32, -1) else 0),
64 => try self.addImm64(if (op == .add) @bitCast(u64, @as(i64, -1)) else 0),
else => unreachable,
}
try self.emitWValue(bin_result);
try self.emitWValue(cmp_result);
}
try self.addTag(.select);
const result = try self.allocLocal(ty);
try self.addLabel(.local_set, result.local);
return result;
}