[Bug sanitizer/61978] implement blacklist for sanitizer

["manu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61978

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |manu at gcc dot gnu.org

--- Comment #10 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Stewart Martin-Haugh from comment #9)
> Hi,
> I see this marked as WONTFIX - still, the use-cases that Kostya identifies
> are valid, I think. Would anyone be able to implement a patch, or suggest
> roughly how this might work?

Although existing GCC devs may not find this feature interesting enough to
implement it themselves, a nice, small patch properly submitted together with a
convincingly argued rationale may get accepted. It seems this feature is being
used not only by Chromium but also by LibreOffice, and many GCC users would
still like to keep using GCC for building those programs.

Many features that were initially rejected have been later accepted (e.g.,
color diagnostics). It just needs someone to get behind the idea and push for
it in the right way.
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From: "terry.guo at arm dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/65648] New: [5 Regression] Bad code due to IRA fails to recognize the clobber in parallel
Date: Wed, 01 Apr 2015 09:44:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide648

            Bug ID: 65648
           Summary: [5 Regression] Bad code due to IRA fails to recognize
                    the clobber in parallel
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: terry.guo at arm dot com

Created attachment 35200
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id5200&actioníit
test case

When compile attached case with command:
arm-none-eabi-gcc -march=armv6-m -mthumb -Os x.c -S

The gcc generates bad code as below:
main:
        push    {r0, r1, r2, r4, r5, r6, r7, lr}
        ldr     r4, .L5
        movs    r5, #0
        ldr     r0, [r4, #8]
        add     r1, sp, #4
        rsbs    r2, r0, #0
        adcs    r2, r2, r0
        subs    r3, r2, r3  //r3 is used but not initialized

The instruction to initialize r3 is removed due to IRA failed to recognize the
clobber in reload pass. Before the reload pass, we have three instructions like
below:
(insn 12 11 14 2 (parallel [
            (set (reg:SI 128)
                (eq:SI (reg:SI 110 [ D.4914 ])
                    (const_int 0 [0])))
            (clobber (reg:SI 129))
        ]) x.c:23 760 {*cstoresi_eq0_thumb1_insn}
     (expr_list:REG_UNUSED (reg:SI 129)
        (nil)))
(insn 20 19 22 2 (set (reg:SI 135)
        (plus:SI (plus:SI (reg:SI 136)
                (reg:SI 137))
            (geu:SI (reg:SI 131 [ D.4914 ])
                (reg:SI 134 [ c ])))) x.c:23 764 {thumb1_addsi3_addgeu}
     (expr_list:REG_DEAD (reg:SI 137)
        (expr_list:REG_DEAD (reg:SI 136)
            (expr_list:REG_DEAD (reg:SI 134 [ c ])
                (expr_list:REG_DEAD (reg:SI 131 [ D.4914 ])
                    (nil))))))
(insn 22 20 23 2 (set (reg:SI 138)
        (minus:SI (reg:SI 128)
            (reg:SI 135))) x.c:23 720 {thumb1_subsi3_insn}
     (expr_list:REG_DEAD (reg:SI 135)
        (expr_list:REG_DEAD (reg:SI 128)
            (nil))))

After the reload pass, those instructions are wrongly turned into:
(insn 20 53 58 2 (set (reg:SI 3 r3 [135])
        (plus:SI (plus:SI (reg:SI 3 r3 [137])
                (reg:SI 2 r2 [136]))
            (geu:SI (reg:SI 7 r7 [orig:131 D.4914 ] [131])
                (reg:SI 6 r6 [153])))) x.c:23 764 {thumb1_addsi3_addgeu}
     (nil))
(insn 58 20 55 2 (parallel [
            (set (reg:SI 2 r2 [128])
                (eq:SI (reg:SI 0 r0 [orig:110 D.4914 ] [110])
                    (const_int 0 [0])))
            (clobber (reg:SI 3 r3 [129]))
        ]) x.c:23 760 {*cstoresi_eq0_thumb1_insn}
     (nil))
(note 55 58 22 2 NOTE_INSN_DELETED)
(insn 22 55 23 2 (set (reg:SI 3 r3 [138])
        (minus:SI (reg:SI 2 r2 [128])
            (reg:SI 3 r3 [135]))) x.c:23 720 {thumb1_subsi3_insn}
     (nil))

However the later pass can recognize the clobber in insn 58 and will remove the
insn 20 because the r3 defined in insn 20 is clobbered by insn 58.