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* [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c
@ 2020-05-15 21:08 simark at simark dot ca
2020-05-15 21:08 ` [Bug tdep/26000] " simark at simark dot ca
` (7 more replies)
0 siblings, 8 replies; 9+ messages in thread
From: simark at simark dot ca @ 2020-05-15 21:08 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
Bug ID: 26000
Summary: -Wtautological-bitwise-compare error in arm-tdep.c
Product: gdb
Version: HEAD
Status: NEW
Severity: normal
Priority: P2
Component: tdep
Assignee: unassigned at sourceware dot org
Reporter: simark at simark dot ca
Target Milestone: ---
We get this error in arm-tdep.c when building with clang 11:
CXX arm-tdep.o
/home/smarchi/src/binutils-gdb/gdb/arm-tdep.c:934:29: error: bitwise comparison
always evaluates to false [-Werror,-Wtautological-bitwise-compare]
else if ((insn & 0xffb0) == 0xe950 /* ldrd Rt, Rt2,
~~~~~~~~~~~~~~~~^~~~~~~~~
Indeed, this can never evaluate to true.
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* [Bug tdep/26000] -Wtautological-bitwise-compare error in arm-tdep.c
2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
@ 2020-05-15 21:08 ` simark at simark dot ca
2020-05-15 22:41 ` luis.machado at linaro dot org
` (6 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: simark at simark dot ca @ 2020-05-15 21:08 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
Simon Marchi <simark at simark dot ca> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at sourceware dot org |luis.machado at linaro dot org
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* [Bug tdep/26000] -Wtautological-bitwise-compare error in arm-tdep.c
2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
2020-05-15 21:08 ` [Bug tdep/26000] " simark at simark dot ca
@ 2020-05-15 22:41 ` luis.machado at linaro dot org
2020-05-15 22:45 ` simark at simark dot ca
` (5 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: luis.machado at linaro dot org @ 2020-05-15 22:41 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
Luis Machado <luis.machado at linaro dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
--- Comment #1 from Luis Machado <luis.machado at linaro dot org> ---
As was discussed on IRC, Simon hinted at problems handling these ldrd/strd's.
Even when fixing the pattern to match ldrd (immediate), with mask 0xff50, the
mask isn't strict enough to match *only* ldrd (immediate). It will also match
ldrd (literal). So we need to verify op1 != 1111 to rule out ldrd (literal).
Then there is the question of whether we want to handle all variants of
ldrd/strd's, which may or may not be important to fix.
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* [Bug tdep/26000] -Wtautological-bitwise-compare error in arm-tdep.c
2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
2020-05-15 21:08 ` [Bug tdep/26000] " simark at simark dot ca
2020-05-15 22:41 ` luis.machado at linaro dot org
@ 2020-05-15 22:45 ` simark at simark dot ca
2020-05-16 2:49 ` luis.machado at linaro dot org
` (4 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: simark at simark dot ca @ 2020-05-15 22:45 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
--- Comment #2 from Simon Marchi <simark at simark dot ca> ---
(In reply to Luis Machado from comment #1)
> As was discussed on IRC, Simon hinted at problems handling these ldrd/strd's.
>
> Even when fixing the pattern to match ldrd (immediate), with mask 0xff50,
> the mask isn't strict enough to match *only* ldrd (immediate). It will also
> match ldrd (literal). So we need to verify op1 != 1111 to rule out ldrd
> (literal).
>
> Then there is the question of whether we want to handle all variants of
> ldrd/strd's, which may or may not be important to fix.
To clarify, could you show here what's the full condition you would use with
mask 0xff50?
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* [Bug tdep/26000] -Wtautological-bitwise-compare error in arm-tdep.c
2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
` (2 preceding siblings ...)
2020-05-15 22:45 ` simark at simark dot ca
@ 2020-05-16 2:49 ` luis.machado at linaro dot org
2020-05-16 2:49 ` luis.machado at linaro dot org
` (3 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: luis.machado at linaro dot org @ 2020-05-16 2:49 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
--- Comment #3 from Luis Machado <luis.machado at linaro dot org> ---
Created attachment 12548
--> https://sourceware.org/bugzilla/attachment.cgi?id=12548&action=edit
Tentative patch
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* [Bug tdep/26000] -Wtautological-bitwise-compare error in arm-tdep.c
2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
` (3 preceding siblings ...)
2020-05-16 2:49 ` luis.machado at linaro dot org
@ 2020-05-16 2:49 ` luis.machado at linaro dot org
2020-05-16 2:53 ` luis.machado at linaro dot org
` (2 subsequent siblings)
7 siblings, 0 replies; 9+ messages in thread
From: luis.machado at linaro dot org @ 2020-05-16 2:49 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
--- Comment #4 from Luis Machado <luis.machado at linaro dot org> ---
This is what i plan to submit as a fix, after i'm done with testing.
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* [Bug tdep/26000] -Wtautological-bitwise-compare error in arm-tdep.c
2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
` (4 preceding siblings ...)
2020-05-16 2:49 ` luis.machado at linaro dot org
@ 2020-05-16 2:53 ` luis.machado at linaro dot org
2020-05-27 12:43 ` cvs-commit at gcc dot gnu.org
2020-05-27 12:44 ` luis.machado at linaro dot org
7 siblings, 0 replies; 9+ messages in thread
From: luis.machado at linaro dot org @ 2020-05-16 2:53 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
Luis Machado <luis.machado at linaro dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Attachment #12548|0 |1
is obsolete| |
--- Comment #5 from Luis Machado <luis.machado at linaro dot org> ---
Created attachment 12549
--> https://sourceware.org/bugzilla/attachment.cgi?id=12549&action=edit
Tentative patch
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* [Bug tdep/26000] -Wtautological-bitwise-compare error in arm-tdep.c
2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
` (5 preceding siblings ...)
2020-05-16 2:53 ` luis.machado at linaro dot org
@ 2020-05-27 12:43 ` cvs-commit at gcc dot gnu.org
2020-05-27 12:44 ` luis.machado at linaro dot org
7 siblings, 0 replies; 9+ messages in thread
From: cvs-commit at gcc dot gnu.org @ 2020-05-27 12:43 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
--- Comment #6 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Luis Machado <luisgpm@sourceware.org>:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=f8c6d1528c19b11fdaa3ec949147280e500446e2
commit f8c6d1528c19b11fdaa3ec949147280e500446e2
Author: Luis Machado <luis.machado@linaro.org>
Date: Fri May 15 23:06:52 2020 -0300
Fix PR 26000, logical bitwise error / prologue analyzer
This fixes an instruction mask typo. We should be matching only
ldrd (immediate) and not any other of its variants. As is, it never matches
anything.
With the patch, the instruction mask also allows matching of ldrd
(literal),
but the check for SP discards this particular instruction pattern, as it
has
a hardcoded PC register.
gdb/ChangeLog:
2020-05-27 Luis Machado <luis.machado@linaro.org>
PR tdep/26000
* arm-tdep.c (thumb_analyze_prologue): Fix instruction matching
for ldrd (immediate).
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* [Bug tdep/26000] -Wtautological-bitwise-compare error in arm-tdep.c
2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
` (6 preceding siblings ...)
2020-05-27 12:43 ` cvs-commit at gcc dot gnu.org
@ 2020-05-27 12:44 ` luis.machado at linaro dot org
7 siblings, 0 replies; 9+ messages in thread
From: luis.machado at linaro dot org @ 2020-05-27 12:44 UTC (permalink / raw)
To: gdb-prs
https://sourceware.org/bugzilla/show_bug.cgi?id=26000
Luis Machado <luis.machado at linaro dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution|--- |FIXED
--- Comment #7 from Luis Machado <luis.machado at linaro dot org> ---
Fixed with the last patch.
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end of thread, other threads:[~2020-05-27 12:44 UTC | newest]
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2020-05-15 21:08 [Bug tdep/26000] New: -Wtautological-bitwise-compare error in arm-tdep.c simark at simark dot ca
2020-05-15 21:08 ` [Bug tdep/26000] " simark at simark dot ca
2020-05-15 22:41 ` luis.machado at linaro dot org
2020-05-15 22:45 ` simark at simark dot ca
2020-05-16 2:49 ` luis.machado at linaro dot org
2020-05-16 2:49 ` luis.machado at linaro dot org
2020-05-16 2:53 ` luis.machado at linaro dot org
2020-05-27 12:43 ` cvs-commit at gcc dot gnu.org
2020-05-27 12:44 ` luis.machado at linaro dot org
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