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wasm: saturating add and sub for signed integers

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This commit is contained in:
Luuk de Gram 2022-06-15 22:03:18 +02:00
parent fcd4280a8c
commit ce5d934f5f
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GPG Key ID: A8CFE58E4DC7D664
1 changed files with 67 additions and 18 deletions
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85
src/arch/wasm/CodeGen.zig
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@ -4885,8 +4885,8 @@ fn airSatBinOp(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
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 lhs = try self.resolveInst(bin_op.lhs);
const rhs = try self.resolveInst(bin_op.rhs);
const int_info = ty.intInfo(self.target);
const is_signed = int_info.signedness == .signed;
@ -4895,22 +4895,12 @@ fn airSatBinOp(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
return self.fail("TODO: saturating arithmetic for integers with bitsize '{d}'", .{int_info.bits});
}
if (is_signed) {
return signedSat(self, lhs, rhs, ty, op);
}
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);
const bin_result = try self.binOp(lhs, rhs, ty, op);
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) {
@ -4919,7 +4909,7 @@ fn airSatBinOp(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
else => unreachable,
};
const cmp_result = try self.cmp(bin_result, imm_val, ty, if (op == .add) .lt else .gt);
const cmp_result = try self.cmp(bin_result, imm_val, ty, .lt);
try self.emitWValue(bin_result);
try self.emitWValue(imm_val);
try self.emitWValue(cmp_result);
@ -4939,3 +4929,62 @@ fn airSatBinOp(self: *Self, inst: Air.Inst.Index, op: Op) InnerError!WValue {
try self.addLabel(.local_set, result.local);
return result;
}
fn signedSat(self: *Self, lhs_operand: WValue, rhs_operand: WValue, ty: Type, op: Op) InnerError!WValue {
const int_info = ty.intInfo(self.target);
const wasm_bits = toWasmBits(int_info.bits).?;
const is_wasm_bits = wasm_bits == int_info.bits;
const lhs = if (!is_wasm_bits) try self.signAbsValue(lhs_operand, ty) else lhs_operand;
const rhs = if (!is_wasm_bits) try self.signAbsValue(rhs_operand, ty) else rhs_operand;
const max_val: u64 = @intCast(u64, (@as(u65, 1) << @intCast(u7, int_info.bits - 1)) - 1);
const min_val = @intCast(i64, ~@intCast(u63, max_val));
const max_wvalue = switch (wasm_bits) {
32 => WValue{ .imm32 = @intCast(u32, max_val) },
64 => WValue{ .imm64 = max_val },
else => unreachable,
};
const min_wvalue = switch (wasm_bits) {
32 => WValue{ .imm32 = @bitCast(u32, @truncate(i32, min_val)) },
64 => WValue{ .imm64 = @bitCast(u64, min_val) },
else => unreachable,
};
const bin_result = try self.binOp(lhs, rhs, ty, op);
if (!is_wasm_bits) {
const cmp_result_lt = try self.cmp(bin_result, max_wvalue, ty, .lt);
try self.emitWValue(bin_result);
try self.emitWValue(max_wvalue);
try self.emitWValue(cmp_result_lt);
try self.addTag(.select);
try self.addLabel(.local_set, bin_result.local); // re-use local
const cmp_result_gt = try self.cmp(bin_result, min_wvalue, ty, .gt);
try self.emitWValue(bin_result);
try self.emitWValue(min_wvalue);
try self.emitWValue(cmp_result_gt);
try self.addTag(.select);
try self.addLabel(.local_set, bin_result.local); // re-use local
return self.wrapOperand(bin_result, ty);
} else {
const zero = switch (wasm_bits) {
32 => WValue{ .imm32 = 0 },
64 => WValue{ .imm64 = 0 },
else => unreachable,
};
const cmp_bin_result = try self.cmp(bin_result, lhs, ty, .lt);
const cmp_zero_result = try self.cmp(rhs, zero, ty, if (op == .add) .lt else .gt);
const xor = try self.binOp(cmp_zero_result, cmp_bin_result, ty, .xor);
const cmp_bin_zero_result = try self.cmp(bin_result, zero, ty, .lt);
try self.emitWValue(max_wvalue);
try self.emitWValue(min_wvalue);
try self.emitWValue(cmp_bin_zero_result);
try self.addTag(.select);
try self.emitWValue(bin_result);
try self.emitWValue(xor);
try self.addTag(.select);
try self.addLabel(.local_set, bin_result.local); // re-use local
return bin_result;
}
}