[Bug rtl-optimization/35604] New: Label references are not updated after edge insertion

[Bug rtl-optimization/35604] New: Label references are not updated after edge insertion

[ubizjak at gmail dot com]

This problem can be seen by compiling testsuite/gfortran.dg/g77/ndrm2.f. The
label reference (after x87 stack compensation edge is inserted) is updated only
in final jump insn, but other references to the same label are left untouched.

We enter stack pass with:

(insn:TI 19 20 18 4 dnrm2.f:33 (set (reg/v/f:SI 1 dx [orig:73 next.2 ] [73])
        (label_ref:SI 53)) 47 {*movsi_1} (expr_list:REG_EQUAL (label_ref:SI 53)
        (insn_list:REG_LABEL_OPERAND 53 (nil))))

...

(insn 23 137 17 4 dnrm2.f:40 (set (reg:CCZ 17 flags)
        (compare:CCZ (reg/v/f:SI 1 dx [orig:73 next.2 ] [73])
            (label_ref:SI 53))) 5 {*cmpsi_1_insn} (insn_list:REG_LABEL_OPERAND
53 (nil)))

...

(jump_insn 24 245 355 4 dnrm2.f:40 (set (pc)
        (if_then_else (eq (reg:CCZ 17 flags)
                (const_int 0 [0x0]))
            (label_ref 53)
            (pc))) 579 {*jcc_1} (expr_list:REG_DEAD (reg:CCZ 17 flags)
        (expr_list:REG_BR_PROB (const_int 1500 [0x5dc])
            (nil))))

;; End of basic block 4 -> ( 13 5)
;; lr  out       1 [dx] 3 [bx] 4 [si] 6 [bp] 7 [sp] 11 [st(3)] 12 [st(4)] 20
[frame]
;; live  out     1 [dx] 3 [bx] 4 [si] 6 [bp] 7 [sp] 12 [st(4)] 20 [frame]

;; Succ edge  13 [15.0%]  (can_fallthru)
;; Succ edge  5 [85.0%]  (fallthru,can_fallthru)


Where the target code label is in BB13:

;; Pred edge  4 [15.0%]  (can_fallthru)
;; Pred edge  12 [15.0%]  (fallthru,can_fallthru)
(code_label/s:HI 53 325 54 13 3 ("__label_000030") [6 uses])

(note:HI 54 53 59 13 [bb 13] NOTE_INSN_BASIC_BLOCK)

====

The BB is inserted on edge between bb4 and bb13, the target code label is now
label 435 in bb37:

;; Start of basic block ( 4) -> 37
;; bb 37 artificial_defs: { }
;; bb 37 artificial_uses: { u-1(6){ }u-1(7){ }}

;; Pred edge  4 [15.0%]  (can_fallthru)
(code_label 435 433 434 37 31 "" [1 uses])

(note 434 435 381 37 [bb 37] NOTE_INSN_BASIC_BLOCK)

(insn 381 434 380 37 (set (reg:DF 9 st(1))
        (reg:DF 8 st)) -1 (expr_list:REG_DEAD (reg:DF 8 st)
        (nil)))

(note 380 381 53 37 NOTE_INSN_DELETED)
;; End of basic block 37 -> ( 13)


;; Succ edge  13 [100.0%]  (fallthru)

===

However, the problem is, that (insn 19) and (insn 23) still point to old label,
producing effectively wrong code:

>>      movl    $.L3, %edx      #, next.2
        movl    $1, %ebx        #, ix
        sall    $3, %eax        #,
>>      cmpl    $.L3, %edx      #, next.2
        movl    $1, -28(%ebp)   #, i
        fldz
        movl    %eax, -20(%ebp) #,
>>      je      .L31    #,

This works only by pure luck.

However, with my experimental patch that produces fused compare-and-branch (a
feature of core2 processor), we enter stack pass with:

(jump_insn:TI 24 245 354 4 dnrm2.f:40 (set (pc)
        (if_then_else (eq (reg/v/f:SI 1 dx [orig:73 next.2 ] [73])
                (label_ref:SI 53))
            (label_ref 53)
            (pc))) 581 {*jcc_fused_1} (insn_list:REG_LABEL_OPERAND 53
(expr_list:REG_BR_PROB (const_int 1500 [0x5dc])
            (nil))))

All label references are updated in a fused jump insn after edge insertion, so
this partially updated sequence is produced:

(insn 19 137 17 4 dnrm2.f:33 (set (reg/v/f:SI 1 dx [orig:73 next.2 ] [73])
        (label_ref:SI 53)) 47 {*movsi_1} (expr_list:REG_EQUAL (label_ref:SI 53)
        (insn_list:REG_LABEL_OPERAND 53 (nil))))

...

(jump_insn:TI 24 245 354 4 dnrm2.f:40 (set (pc)
        (if_then_else (eq (reg/v/f:SI 1 dx [orig:73 next.2 ] [73])
                (label_ref:SI 434))
            (label_ref:SI 434)
            (pc))) 581 {*jcc_fused_1} (insn_list:REG_LABEL_OPERAND 53
(expr_list:REG_BR_PROB (const_int 1500 [0x5dc])
            (nil))))


leading to:

>>>     movl    $.L3, %edx
        movl    $1, -28(%ebp)
        movl    $1, %ebx
        fldz
        movl    %eax, -20(%ebp)
        .p2align 4,,7
>>>     cmpl    $.L31, %edx
>>>     je      .L31    # fused

This is still wrong code, but triggers a testsuite failure. And by changing
$.L3 into $.L31, the test succeeds also with fused compare and branch.

The conclusion is, that updating only jump insn is not enough, but all label
references should be updated to newly inserted label when edge is inserted into
control flow.


-- 
           Summary: Label references are not updated after edge insertion
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: rtl-optimization
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: ubizjak at gmail dot com
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604

[Bug rtl-optimization/35604] Label references are not updated after edge insertion

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2008-03-16 10:57 -------
*** Bug 35605 has been marked as a duplicate of this bug. ***


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604

[Bug rtl-optimization/35604] Label references are not updated after edge insertion

[ubizjak at gmail dot com]

------- Comment #2 from ubizjak at gmail dot com  2008-06-14 11:17 -------
For the reference, proposed patch for fused macro ops is at
http://gcc.gnu.org/ml/gcc-patches/2008-03/msg00969.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604

[Bug rtl-optimization/35604] Label references are not updated after edge insertion

[hjl dot tools at gmail dot com]

------- Comment #3 from hjl dot tools at gmail dot com  2008-06-14 14:55 -------
Joey, Xuepeng, Weiliang, can we try

http://gcc.gnu.org/ml/gcc-patches/2008-03/msg00969.html

on SPEC CPU 2K/2006 for both 32bit and 64bit?


-- 

hjl dot tools at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hjl dot tools at gmail dot
                   |                            |com, Joey dot ye at intel
                   |                            |dot com, weiliang dot lin at
                   |                            |intel dot com, xuepeng dot
                   |                            |guo at intel dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604

[Bug rtl-optimization/35604] Label references are not updated after edge insertion

[ubizjak at gmail dot com]

------- Comment #4 from ubizjak at gmail dot com  2008-06-18 15:00 -------
PAtch for generic RTL problem with compare-and-branch instruction is at
http://gcc.gnu.org/ml/gcc-patches/2008-06/msg01141.html.


-- 

ubizjak at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |ubizjak at gmail dot com
                   |dot org                     |
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2008-06-18 15:00:58
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604

[Bug rtl-optimization/35604] Label references are not updated after edge insertion

[uros at gcc dot gnu dot org]

------- Comment #5 from uros at gcc dot gnu dot org  2008-06-18 17:16 -------
Subject: Bug 35604

Author: uros
Date: Wed Jun 18 17:16:05 2008
New Revision: 136899

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=136899
Log:
        PR rtl-optimization/35604
        * jump.c (redirect_exp_1): Skip the condition of an IF_THEN_ELSE. We
        only want to change jump destinations, not eventual label comparisons.


Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/jump.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604

[Bug rtl-optimization/35604] Label references are not updated after edge insertion

[ubizjak at gmail dot com]

------- Comment #6 from ubizjak at gmail dot com  2008-06-18 17:20 -------
Fixed in mainline, patch will be backport to 4.3 branch in a couple of days.


-- 

ubizjak at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604

[Bug rtl-optimization/35604] Label references are not updated after edge insertion

[uros at gcc dot gnu dot org]

------- Comment #7 from uros at gcc dot gnu dot org  2008-06-19 14:05 -------
Subject: Bug 35604

Author: uros
Date: Thu Jun 19 14:04:31 2008
New Revision: 136947

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=136947
Log:
        PR rtl-optimization/35604
        * jump.c (redirect_exp_1): Skip the condition of an IF_THEN_ELSE. We
        only want to change jump destinations, not eventual label comparisons.


Modified:
    branches/gcc-4_3-branch/gcc/ChangeLog
    branches/gcc-4_3-branch/gcc/jump.c


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604

[Bug rtl-optimization/35604] Label references are not updated after edge insertion

[ubizjak at gmail dot com]

-- 

ubizjak at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.3.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35604