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x86_64: optimize wide mul with overflow

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This commit is contained in:
Jacob Young 2023-04-29 17:56:48 -04:00
parent 3c2636a83d
commit c81878978a
1 changed files with 36 additions and 25 deletions
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61
src/arch/x86_64/CodeGen.zig
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@ -2520,7 +2520,7 @@ fn genSetFrameTruncatedOverflowCompare(
tuple_ty: Type,
frame_index: FrameIndex,
src_mcv: MCValue,
cc: Condition,
overflow_cc: ?Condition,
) !void {
const src_lock = switch (src_mcv) {
.register => |reg| self.register_manager.lockReg(reg),
@ -2551,7 +2551,7 @@ fn genSetFrameTruncatedOverflowCompare(
defer for (temp_locks) |lock| self.register_manager.unlockReg(lock);
const overflow_reg = temp_regs[0];
try self.asmSetccRegister(overflow_reg.to8(), cc);
if (overflow_cc) |cc| try self.asmSetccRegister(overflow_reg.to8(), cc);
const scratch_reg = temp_regs[1];
const hi_limb_off = if (int_info.bits <= 64) 0 else (int_info.bits - 1) / 64 * 8;
@ -2564,8 +2564,10 @@ fn genSetFrameTruncatedOverflowCompare(
try self.genBinOpMir(.cmp, hi_limb_ty, .{ .register = scratch_reg }, hi_limb_mcv);
const eq_reg = temp_regs[2];
try self.asmSetccRegister(eq_reg.to8(), .ne);
try self.genBinOpMir(.@"or", Type.u8, .{ .register = overflow_reg }, .{ .register = eq_reg });
if (overflow_cc) |_| {
try self.asmSetccRegister(eq_reg.to8(), .ne);
try self.genBinOpMir(.@"or", Type.u8, .{ .register = overflow_reg }, .{ .register = eq_reg });
}
const payload_off = @intCast(i32, tuple_ty.structFieldOffset(0, self.target.*));
if (hi_limb_off > 0) try self.genSetMem(.{ .frame = frame_index }, payload_off, rest_ty, src_mcv);
@ -2579,7 +2581,7 @@ fn genSetFrameTruncatedOverflowCompare(
.{ .frame = frame_index },
@intCast(i32, tuple_ty.structFieldOffset(1, self.target.*)),
tuple_ty.structFieldType(1),
.{ .register = overflow_reg.to8() },
if (overflow_cc) |_| .{ .register = overflow_reg.to8() } else .{ .eflags = .ne },
);
}
@ -2654,27 +2656,36 @@ fn airMulWithOverflow(self: *Self, inst: Air.Inst.Index) !void {
try self.genSetFrameTruncatedOverflowCompare(tuple_ty, frame_index, partial_mcv, cc);
break :result .{ .load_frame = .{ .index = frame_index } };
},
// For now, this is the only supported multiply that doesn't fit in a register.
else => assert(dst_info.bits <= 128 and src_pl.data == 64),
}
else => {
// For now, this is the only supported multiply that doesn't fit in a register,
// so cc being set is impossible.
const frame_index =
try self.allocFrameIndex(FrameAlloc.initType(tuple_ty, self.target.*));
if (dst_info.bits >= lhs_active_bits + rhs_active_bits) {
try self.genSetMem(
.{ .frame = frame_index },
@intCast(i32, tuple_ty.structFieldOffset(0, self.target.*)),
tuple_ty.structFieldType(0),
partial_mcv,
);
try self.genSetMem(
.{ .frame = frame_index },
@intCast(i32, tuple_ty.structFieldOffset(1, self.target.*)),
tuple_ty.structFieldType(1),
.{ .immediate = 0 }, // overflow is impossible for 64-bit*64-bit -> 128-bit
);
} else try self.genSetFrameTruncatedOverflowCompare(tuple_ty, frame_index, partial_mcv, cc);
break :result .{ .load_frame = .{ .index = frame_index } };
assert(dst_info.bits <= 128 and src_pl.data == 64);
const frame_index =
try self.allocFrameIndex(FrameAlloc.initType(tuple_ty, self.target.*));
if (dst_info.bits >= lhs_active_bits + rhs_active_bits) {
try self.genSetMem(
.{ .frame = frame_index },
@intCast(i32, tuple_ty.structFieldOffset(0, self.target.*)),
tuple_ty.structFieldType(0),
partial_mcv,
);
try self.genSetMem(
.{ .frame = frame_index },
@intCast(i32, tuple_ty.structFieldOffset(1, self.target.*)),
tuple_ty.structFieldType(1),
.{ .immediate = 0 },
);
} else try self.genSetFrameTruncatedOverflowCompare(
tuple_ty,
frame_index,
partial_mcv,
null,
);
break :result .{ .load_frame = .{ .index = frame_index } };
},
}
},
else => unreachable,
};