On Mon, Sep 21, 2020 at 10:49:17AM -0500, Segher Boessenkool wrote:
> Hi!
>
> On Thu, Sep 17, 2020 at 01:12:19PM +0930, Alan Modra wrote:
> > On Wed, Sep 16, 2020 at 07:02:06PM -0500, Segher Boessenkool wrote:
> > > > + /* Test both regs even though the one in the mask is
> > > > + constrained to be equal to the output. Increasing
> > > > + cost may well result in rejecting an invalid insn
> > > > + earlier. */
> > >
> > > Is that ever actually useful?
> >
> > Possibly not in this particular case, but I did see cases where
> > invalid insns were rejected early by costing non-reg sub-expressions.
>
> But does that ever change generated code?
>
> This makes the compiler a lot harder to read and understand. To the
> point that such micro-optimisations makes worthwhile optimisations hard
> or impossible to do.
Fair enough, here's a revised patch.
* config/rs6000/rs6000.c (rotate_insert_cost): New function.
(rs6000_rtx_costs): Cost IOR. Tidy break/return. Tidy AND.
diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 5025e3c30c0..78c33cc8cba 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -21118,6 +21118,91 @@ rs6000_cannot_copy_insn_p (rtx_insn *insn)
&& get_attr_cannot_copy (insn);
}
+/* Handle rtx_costs for scalar integer rotate and insert insns. */
+
+static bool
+rotate_insert_cost (rtx left, rtx right, machine_mode mode, bool speed,
+ int *total)
+{
+ if (GET_CODE (right) == AND
+ && CONST_INT_P (XEXP (right, 1))
+ && UINTVAL (XEXP (left, 1)) + UINTVAL (XEXP (right, 1)) + 1 == 0)
+ {
+ rtx leftop = XEXP (left, 0);
+ rtx rightop = XEXP (right, 0);
+
+ /* rotlsi3_insert_5. */
+ if (REG_P (leftop)
+ && REG_P (rightop)
+ && mode == SImode
+ && UINTVAL (XEXP (left, 1)) != 0
+ && UINTVAL (XEXP (right, 1)) != 0
+ && rs6000_is_valid_mask (XEXP (left, 1), NULL, NULL, mode))
+ return true;
+ /* rotldi3_insert_6. */
+ if (REG_P (leftop)
+ && REG_P (rightop)
+ && mode == DImode
+ && exact_log2 (-UINTVAL (XEXP (left, 1))) > 0)
+ return true;
+ /* rotldi3_insert_7. */
+ if (REG_P (leftop)
+ && REG_P (rightop)
+ && mode == DImode
+ && exact_log2 (-UINTVAL (XEXP (right, 1))) > 0)
+ return true;
+
+ rtx mask = 0;
+ rtx shift = leftop;
+ rtx_code shift_code = GET_CODE (shift);
+ /* rotl<mode>3_insert. */
+ if (shift_code == ROTATE
+ || shift_code == ASHIFT
+ || shift_code == LSHIFTRT)
+ mask = right;
+ else
+ {
+ shift = rightop;
+ shift_code = GET_CODE (shift);
+ /* rotl<mode>3_insert_2. */
+ if (shift_code == ROTATE
+ || shift_code == ASHIFT
+ || shift_code == LSHIFTRT)
+ mask = left;
+ }
+ if (mask
+ && CONST_INT_P (XEXP (shift, 1))
+ && rs6000_is_valid_insert_mask (XEXP (mask, 1), shift, mode))
+ {
+ *total += rtx_cost (XEXP (shift, 0), mode, shift_code, 0, speed);
+ *total += rtx_cost (XEXP (mask, 0), mode, AND, 0, speed);
+ return true;
+ }
+ }
+ /* rotl<mode>3_insert_3. */
+ if (GET_CODE (right) == ASHIFT
+ && CONST_INT_P (XEXP (right, 1))
+ && (INTVAL (XEXP (right, 1))
+ == exact_log2 (UINTVAL (XEXP (left, 1)) + 1)))
+ {
+ *total += rtx_cost (XEXP (left, 0), mode, AND, 0, speed);
+ *total += rtx_cost (XEXP (right, 0), mode, ASHIFT, 0, speed);
+ return true;
+ }
+ /* rotl<mode>3_insert_4. */
+ if (GET_CODE (right) == LSHIFTRT
+ && CONST_INT_P (XEXP (right, 1))
+ && mode == SImode
+ && (INTVAL (XEXP (right, 1))
+ + exact_log2 (-UINTVAL (XEXP (left, 1)))) == 32)
+ {
+ *total += rtx_cost (XEXP (left, 0), mode, AND, 0, speed);
+ *total += rtx_cost (XEXP (right, 0), mode, LSHIFTRT, 0, speed);
+ return true;
+ }
+ return false;
+}
+
/* Compute a (partial) cost for rtx X. Return true if the complete
cost has been computed, and false if subexpressions should be
scanned. In either case, *TOTAL contains the cost result.
@@ -21165,6 +21250,7 @@ static bool
rs6000_rtx_costs (rtx x, machine_mode mode, int outer_code,
int opno ATTRIBUTE_UNUSED, int *total, bool speed)
{
+ rtx left, right;
int code = GET_CODE (x);
switch (code)
@@ -21295,7 +21381,7 @@ rs6000_rtx_costs (rtx x, machine_mode mode, int
outer_code,
*total = rs6000_cost->fp;
else
*total = rs6000_cost->dmul;
- break;
+ return false;
case DIV:
case MOD:
@@ -21355,32 +21441,37 @@ rs6000_rtx_costs (rtx x, machine_mode mode, int
outer_code,
return false;
case AND:
- if (CONST_INT_P (XEXP (x, 1)))
+ *total = COSTS_N_INSNS (1);
+ right = XEXP (x, 1);
+ if (CONST_INT_P (right))
{
- rtx left = XEXP (x, 0);
+ left = XEXP (x, 0);
rtx_code left_code = GET_CODE (left);
/* rotate-and-mask: 1 insn. */
if ((left_code == ROTATE
|| left_code == ASHIFT
|| left_code == LSHIFTRT)
- && rs6000_is_valid_shift_mask (XEXP (x, 1), left, mode))
+ && rs6000_is_valid_shift_mask (right, left, mode))
{
- *total = rtx_cost (XEXP (left, 0), mode, left_code, 0, speed);
- if (!CONST_INT_P (XEXP (left, 1)))
- *total += rtx_cost (XEXP (left, 1), SImode, left_code, 1,
speed);
- *total += COSTS_N_INSNS (1);
+ *total += rtx_cost (XEXP (left, 0), mode, left_code, 0, speed);
+ *total += rtx_cost (XEXP (left, 1), mode, left_code, 1, speed);
return true;
}
}
-
- *total = COSTS_N_INSNS (1);
return false;
case IOR:
- /* FIXME */
*total = COSTS_N_INSNS (1);
- return true;
+ left = XEXP (x, 0);
+ if (GET_CODE (left) == AND
+ && CONST_INT_P (XEXP (left, 1)))
+ {
+ right = XEXP (x, 1);
+ if (rotate_insert_cost (left, right, mode, speed, total))
+ return true;
+ }
+ return false;
case CLZ:
case XOR:
@@ -21465,7 +21556,7 @@ rs6000_rtx_costs (rtx x, machine_mode mode, int
outer_code,
*total = rs6000_cost->fp;
return false;
}
- break;
+ return false;
case NE:
case EQ:
@@ -21503,13 +21594,11 @@ rs6000_rtx_costs (rtx x, machine_mode mode, int
outer_code,
*total = 0;
return true;
}
- break;
+ return false;
default:
- break;
+ return false;
}
-
- return false;
}
/* Debug form of r6000_rtx_costs that is selected if -mdebug=cost. */
--
Alan Modra
Australia Development Lab, IBM
