mirror of
https://github.com/cc65/cc65.git
synced 2024-12-23 19:29:37 +00:00
LoadExpr: Optimize <= 8-bit bit-field loads
Set CF_FORCECHAR to do as many operations as char ops as possible. Clear high byte at the end.
This commit is contained in:
parent
0c72647edd
commit
d8f9201ecd
@ -117,12 +117,27 @@ void LoadExpr (unsigned Flags, struct ExprDesc* Expr)
|
|||||||
*/
|
*/
|
||||||
unsigned EndBit = 0; /* End bit for bit-fields, or zero if non-bit-field. */
|
unsigned EndBit = 0; /* End bit for bit-fields, or zero if non-bit-field. */
|
||||||
int AdjustBitField = 0;
|
int AdjustBitField = 0;
|
||||||
|
unsigned BitFieldFullWidthFlags = 0;
|
||||||
if (ED_IsBitField (Expr)) {
|
if (ED_IsBitField (Expr)) {
|
||||||
EndBit = Expr->BitOffs + Expr->BitWidth;
|
EndBit = Expr->BitOffs + Expr->BitWidth;
|
||||||
AdjustBitField = Expr->BitOffs != 0 || (EndBit != CHAR_BITS && EndBit != INT_BITS);
|
AdjustBitField = Expr->BitOffs != 0 || (EndBit != CHAR_BITS && EndBit != INT_BITS);
|
||||||
|
|
||||||
|
/* TODO: This probably needs to be guarded by AdjustBitField when long bit-fields are
|
||||||
|
** supported.
|
||||||
|
*/
|
||||||
Flags |= (EndBit <= CHAR_BITS) ? CF_CHAR : CF_INT;
|
Flags |= (EndBit <= CHAR_BITS) ? CF_CHAR : CF_INT;
|
||||||
Flags |= CF_UNSIGNED;
|
Flags |= CF_UNSIGNED;
|
||||||
|
|
||||||
|
/* Flags we need operate on the whole bit-field, without CF_FORCECHAR. */
|
||||||
|
BitFieldFullWidthFlags = Flags;
|
||||||
|
|
||||||
|
/* If we're adjusting, then only load a char (not an int) and do only char ops;
|
||||||
|
** We will clear the high byte in the adjustment. CF_FORCECHAR does nothing if the
|
||||||
|
** type is not CF_CHAR.
|
||||||
|
*/
|
||||||
|
if (AdjustBitField) {
|
||||||
|
Flags |= CF_FORCECHAR;
|
||||||
|
}
|
||||||
} else if ((Flags & CF_TYPEMASK) == 0) {
|
} else if ((Flags & CF_TYPEMASK) == 0) {
|
||||||
Flags |= TypeOf (Expr->Type);
|
Flags |= TypeOf (Expr->Type);
|
||||||
}
|
}
|
||||||
@ -211,10 +226,7 @@ void LoadExpr (unsigned Flags, struct ExprDesc* Expr)
|
|||||||
** so be sure to always use unsigned ints for the operations.
|
** so be sure to always use unsigned ints for the operations.
|
||||||
*/
|
*/
|
||||||
if (AdjustBitField) {
|
if (AdjustBitField) {
|
||||||
/* If the field was loaded as a char, force the shift/mask ops to be char ops.
|
unsigned F = Flags | CF_CONST;
|
||||||
** If it is a char, the load has already put 0 in the upper byte, so that can remain.
|
|
||||||
*/
|
|
||||||
unsigned F = Flags | CF_FORCECHAR | CF_CONST;
|
|
||||||
|
|
||||||
/* We always need to do something with the low byte, so there is no opportunity
|
/* We always need to do something with the low byte, so there is no opportunity
|
||||||
** for optimization by skipping it.
|
** for optimization by skipping it.
|
||||||
@ -242,19 +254,21 @@ void LoadExpr (unsigned Flags, struct ExprDesc* Expr)
|
|||||||
/* Shift right by the bit offset; no code is emitted if BitOffs is zero */
|
/* Shift right by the bit offset; no code is emitted if BitOffs is zero */
|
||||||
g_asr (F, Expr->BitOffs);
|
g_asr (F, Expr->BitOffs);
|
||||||
|
|
||||||
/* Since we have now shifted down, we can do char ops as long as the width fits in
|
/* Since we have now shifted down, we could do char ops when the width fits in
|
||||||
** a char.
|
** a char, but we also need to clear the high byte since we've been using
|
||||||
|
** CF_FORCECHAR up to now.
|
||||||
*/
|
*/
|
||||||
if (Expr->BitWidth <= CHAR_BITS) {
|
|
||||||
F |= CF_CHAR;
|
|
||||||
}
|
|
||||||
|
|
||||||
/* And by the width if the field doesn't end on a char or int boundary.
|
/* And by the width if the field doesn't end on a char or int boundary.
|
||||||
** If it does end on a boundary, then zeros have already been shifted in.
|
** If it does end on a boundary, then zeros have already been shifted in,
|
||||||
** g_and emits no code if the mask is all ones.
|
** but we need to clear the high byte for char. g_and emits no code if the mask
|
||||||
|
** is all ones.
|
||||||
*/
|
*/
|
||||||
if (EndBit != CHAR_BITS && EndBit != INT_BITS) {
|
if (EndBit == CHAR_BITS) {
|
||||||
g_and (F, (0x0001U << Expr->BitWidth) - 1U);
|
/* We need to clear the high byte, since CF_FORCECHAR was set. */
|
||||||
|
g_and (BitFieldFullWidthFlags | CF_CONST, 0xFF);
|
||||||
|
} else if (EndBit != INT_BITS) {
|
||||||
|
g_and (BitFieldFullWidthFlags | CF_CONST, (0x0001U << Expr->BitWidth) - 1U);
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
}
|
}
|
||||||
|
Loading…
Reference in New Issue
Block a user