From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugzilla@gcc.gnu.org>
Received: by sourceware.org (Postfix, from userid 48)
	id D47203858C56; Fri, 14 Oct 2022 07:37:39 +0000 (GMT)
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org D47203858C56
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org;
	s=default; t=1665733059;
	bh=kgRPNyh6UdxU/w3e0lss6wYreN5ei3i8UckRjRk/f3E=;
	h=From:To:Subject:Date:In-Reply-To:References:From;
	b=QZ5vbSxRtWLQifEw1/FoI+NJtfnp3EvuxzMfW9B8dC8nnuBKGcVVvwtioan0JViDz
	 R7LXzq/HbTnE1tSPzLrVYZqGxVe1sw5O9dM5iPrFsI5s6j4C2jZmL5o55GsMundDyU
	 PohkpFOPbe5OwNascu6iNXmHLgkiISE91G06LtWA=
From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/107250] Load unnecessarily happens before malloc
Date: Fri, 14 Oct 2022 07:37:39 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: target
X-Bugzilla-Version: 13.0
X-Bugzilla-Keywords: missed-optimization
X-Bugzilla-Severity: normal
X-Bugzilla-Who: rguenth at gcc dot gnu.org
X-Bugzilla-Status: NEW
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Flags: 
X-Bugzilla-Changed-Fields: keywords component version cf_reconfirmed_on
 bug_status cf_gcctarget everconfirmed
Message-ID: <bug-107250-4-AkCzIStzx7@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-107250-4@http.gcc.gnu.org/bugzilla/>
References: <bug-107250-4@http.gcc.gnu.org/bugzilla/>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
MIME-Version: 1.0
List-Id: <gcc-bugs.sourceware.org>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D107250

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
          Component|tree-optimization           |target
            Version|unknown                     |13.0
   Last reconfirmed|                            |2022-10-14
             Status|UNCONFIRMED                 |NEW
             Target|                            |x86_64-*-*
     Ever confirmed|0                           |1

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
The question is _why_ we generate worse code ... looks like pro/epilogue
generation differs:

@@ -11,15 +11,19 @@
 Attempting shrink-wrapping optimization.
 Block 2 needs prologue due to insn 2:
 (insn 2 4 3 2 (set (reg/v/f:DI 3 bx [orig:84 f ] [84])
-        (reg:DI 5 di [87])) "t.c":4:23 82 {*movdi_internal}
+        (reg:DI 5 di [86])) "t.c":4:23 82 {*movdi_internal}
      (nil))
 After wrapping required blocks, PRO is now 2
 Avoiding non-duplicatable blocks, PRO is now 2
 Bumping back to anticipatable blocks, PRO is now 2
...
     1: NOTE_INSN_DELETED
     4: NOTE_INSN_BASIC_BLOCK 2
-   18: [--sp:DI]=3Dbx:DI
-   19: NOTE_INSN_PROLOGUE_END
+   18: [--sp:DI]=3Dbp:DI
+   19: [--sp:DI]=3Dbx:DI
+   20: {sp:DI=3Dsp:DI-0x8;clobber flags:CC;clobber [scratch];}
+      REG_CFA_ADJUST_CFA sp:DI=3Dsp:DI-0x8
+   21: NOTE_INSN_PROLOGUE_END
     2: bx:DI=3Ddi:DI
     3: NOTE_INSN_FUNCTION_BEG
-    6: di:DI=3D0x8
-    7: ax:DI=3Dcall [`malloc'] argc:0
+    6: bp:DI=3D[bx:DI]
+    7: di:DI=3D0x8
+    8: ax:DI=3Dcall [`malloc'] argc:0
       REG_CALL_DECL `malloc'
       REG_EH_REGION 0
-   10: dx:DI=3D[bx:DI]
-      REG_EQUIV [bx:DI]
-   11: [ax:DI]=3Ddx:DI
+   11: [ax:DI]=3Dbp:DI
    12: [bx:DI]=3Dax:DI
-   20: NOTE_INSN_EPILOGUE_BEG
-   21: bx:DI=3D[sp:DI++]
+   22: NOTE_INSN_EPILOGUE_BEG
+   23: {sp:DI=3Dsp:DI+0x8;clobber flags:CC;clobber [scratch];}
       REG_CFA_ADJUST_CFA sp:DI=3Dsp:DI+0x8
-   22: simple_return
-   25: barrier
+   24: bx:DI=3D[sp:DI++]
+      REG_CFA_ADJUST_CFA sp:DI=3Dsp:DI+0x8
+   25: bp:DI=3D[sp:DI++]
+      REG_CFA_ADJUST_CFA sp:DI=3Dsp:DI+0x8
+   26: simple_return
+   29: barrier
    17: NOTE_INSN_DELETED=