[Bug target/113744] New: Unnecessary "m" constraint in *adddi_4

[Bug target/113744] New: Unnecessary "m" constraint in *adddi_4

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113744

            Bug ID: 113744
           Summary: Unnecessary "m" constraint in *adddi_4
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: hjl.tools at gmail dot com
                CC: crazylht at gmail dot com, hongyuw at gcc dot gnu.org,
                    lingling.kong7 at gmail dot com
  Target Milestone: ---

commit 7abcef725e40589553a079df9258ae094b811751
Author: Kong Lingling <lingling.kong@intel.com>
Date:   Wed Jan 18 17:23:29 2023 +0800

    [APX NDD] Support APX NDD for optimization patterns of add

has

@@ -6994,31 +7021,35 @@ (define_insn "*addsi_3_zext"
 (define_insn "*adddi_4"
   [(set (reg FLAGS_REG)
   (compare
-    (match_operand:DI 1 "nonimmediate_operand" "0")
-    (match_operand:DI 2 "x86_64_immediate_operand" "e")))
-   (clobber (match_scratch:DI 0 "=r"))]
+    (match_operand:DI 1 "nonimmediate_operand" "0,rm")
+    (match_operand:DI 2 "x86_64_immediate_operand" "e,e")))
+   (clobber (match_scratch:DI 0 "=r,r"))]
   "TARGET_64BIT
    && ix86_match_ccmode (insn, CCGCmode)"

But peephole which generates *adddi_4 only supports register as operand 2.

[Bug target/113744] Unnecessary "m" constraint in *adddi_4

[hjl.tools at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113744

--- Comment #1 from H.J. Lu <hjl.tools at gmail dot com> ---
Other *add patterns may have the same issue.

[Bug target/113744] Unnecessary "m" constraint in *adddi_4

[liuhongt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113744

Hongtao Liu <liuhongt at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |liuhongt at gcc dot gnu.org

--- Comment #2 from Hongtao Liu <liuhongt at gcc dot gnu.org> ---
 7018; For comparisons against 1, -1 and 128, we may generate better code
 7019; by converting cmp to add, inc or dec as done by peephole2.  This pattern
 7020; is matched then.  We can't accept general immediate, because for
 7021; case of overflows,  the result is messed up.
 7022; Also carry flag is reversed compared to cmp, so this conversion is valid
 7023; only for comparisons not depending on it.
 7024

It sounds to me those peephole2 can be extended to memory operand since APX_NDD
supports that. So it's not redudant m constraint in the pattern, but miss
optimization in those peepholes.