diff mbox series

aarch64: Improve cost of `a ? {-,}1 : b`

Message ID 20231127043333.1955900-1-quic_apinski@quicinc.com
State Accepted
Headers
Series aarch64: Improve cost of `a ? {-,}1 : b` |

Checks

Context Check Description
snail/gcc-patch-check success Github commit url

Commit Message

Andrew Pinski (QUIC) Nov. 27, 2023, 4:33 a.m. UTC 
  While looking into PR 112454, I found the cost for
`(if_then_else (cmp) (const_int 1) (reg))` was being recorded as 8
(or `COSTS_N_INSNS (2)`) but it should have been 4 (or `COSTS_N_INSNS (1)`).
This improves the cost by not adding the cost of `(const_int 1)` to
the total cost.

It does not does not fix PR 112454 as that requires other changes to forwprop
the `(const_int 1)` earlier than combine.

Bootstrapped and tested on aarch64-linux-gnu with no regressions.

gcc/ChangeLog:

	* config/aarch64/aarch64.cc (aarch64_if_then_else_costs):
	Don't add the cost of `1` or `-1`.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>
---
 gcc/config/aarch64/aarch64.cc | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)
diff mbox series

Patch

diff --git a/gcc/config/aarch64/aarch64.cc b/gcc/config/aarch64/aarch64.cc
index f6f6f94bf43..63241c5aaa5 100644
--- a/gcc/config/aarch64/aarch64.cc
+++ b/gcc/config/aarch64/aarch64.cc
@@ -11642,9 +11642,16 @@  aarch64_if_then_else_costs (rtx op0, rtx op1, rtx op2, int *cost, bool speed)
 	    /* CSINV/NEG with zero extend + const 0 (*csinv3_uxtw_insn3).  */
 	    op1 = XEXP (inner, 0);
 	}
-
-      *cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
-      *cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 2, speed);
+      if (op2 == constm1_rtx || op2 == const1_rtx)
+	*cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
+      else if (op1 == constm1_rtx || op1 == const1_rtx)
+	*cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 2, speed);
+      else
+	{
+	  *cost += rtx_cost (op1, VOIDmode, IF_THEN_ELSE, 1, speed);
+	  *cost += rtx_cost (op2, VOIDmode, IF_THEN_ELSE, 1, speed);
+	}
+      
       return true;
     }