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* [Bug target/57837] New: ARM function pointer tailcall miscompilation regression
@ 2013-07-06 16:16 me at williamgrant dot id.au
2013-07-10 22:34 ` [Bug target/57837] " ramana at gcc dot gnu.org
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: me at williamgrant dot id.au @ 2013-07-06 16:16 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57837
Bug ID: 57837
Summary: ARM function pointer tailcall miscompilation
regression
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: me at williamgrant dot id.au
Created attachment 30469
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30469&action=edit
arm.md fix
The fix for PR target/19599 in svn trunk r198928 causes predicated function
pointer tailcalls for some ARM targets to lose their predicate and execute
unconditionally, resulting in a crash or other misbehaviour. I was able to
reproduce the miscompilation, manifesting as a segfault, using -march=armv4t
-marm -O3, as below:
gcc -march=armv4t -marm -O3 -o bx-test bx-test.c
----
void baz() {};
void (*bar)() = baz;
void foo(int c) {
if (c == 1) {
foo(0);
}
bar();
}
int main(int argc, char **argv) {
foo(1);
}
----
Today's trunk gives the following asm:
----
foo:
cmp r0, #1
stmfd sp!, {r4, lr}
ldr r4, .L8
ldrne r3, [r4]
ldmnefd sp!, {r4, lr}
bx r3 @ indirect register sibling call
----
Note the bx to an r3 that is uninitialised when r0 == 1; it should actually be
a bxne. The bug in arm.md is fairly clear: the %? is missing from two bx
instructions, so the predicate is omitted. After identifying the bad code I
discovered that the issue was raised in review, but deemed irrelevant
(http://gcc.gnu.org/ml/gcc-patches/2013-05/msg01022.html).
The attached patch fixes the bug for me.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/57837] ARM function pointer tailcall miscompilation regression
2013-07-06 16:16 [Bug target/57837] New: ARM function pointer tailcall miscompilation regression me at williamgrant dot id.au
@ 2013-07-10 22:34 ` ramana at gcc dot gnu.org
2013-07-26 7:02 ` bernd.edlinger at hotmail dot de
2013-07-26 8:16 ` ramana at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: ramana at gcc dot gnu.org @ 2013-07-10 22:34 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57837
Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |wrong-code
Status|UNCONFIRMED |NEW
Last reconfirmed| |2013-07-10
CC| |ramana at gcc dot gnu.org
Assignee|unassigned at gcc dot gnu.org |ramana at gcc dot gnu.org
Target Milestone|--- |4.9.0
Ever confirmed|0 |1
--- Comment #1 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
mine.
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/57837] ARM function pointer tailcall miscompilation regression
2013-07-06 16:16 [Bug target/57837] New: ARM function pointer tailcall miscompilation regression me at williamgrant dot id.au
2013-07-10 22:34 ` [Bug target/57837] " ramana at gcc dot gnu.org
@ 2013-07-26 7:02 ` bernd.edlinger at hotmail dot de
2013-07-26 8:16 ` ramana at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: bernd.edlinger at hotmail dot de @ 2013-07-26 7:02 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57837
--- Comment #2 from Bernd Edlinger <bernd.edlinger at hotmail dot de> ---
(In reply to Ramana Radhakrishnan from comment #1)
> mine.
fixed with revision 201240 ?
^ permalink raw reply [flat|nested] 4+ messages in thread
* [Bug target/57837] ARM function pointer tailcall miscompilation regression
2013-07-06 16:16 [Bug target/57837] New: ARM function pointer tailcall miscompilation regression me at williamgrant dot id.au
2013-07-10 22:34 ` [Bug target/57837] " ramana at gcc dot gnu.org
2013-07-26 7:02 ` bernd.edlinger at hotmail dot de
@ 2013-07-26 8:16 ` ramana at gcc dot gnu.org
2 siblings, 0 replies; 4+ messages in thread
From: ramana at gcc dot gnu.org @ 2013-07-26 8:16 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57837
Ramana Radhakrishnan <ramana at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
Resolution|--- |FIXED
--- Comment #3 from Ramana Radhakrishnan <ramana at gcc dot gnu.org> ---
http://gcc.gnu.org/ml/gcc-cvs/2013-07/msg00672.html
http://gcc.gnu.org/ml/gcc-cvs/2013-07/msg00671.html
http://gcc.gnu.org/ml/gcc-cvs/2013-07/msg00670.html
^ permalink raw reply [flat|nested] 4+ messages in thread
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2013-07-06 16:16 [Bug target/57837] New: ARM function pointer tailcall miscompilation regression me at williamgrant dot id.au
2013-07-10 22:34 ` [Bug target/57837] " ramana at gcc dot gnu.org
2013-07-26 7:02 ` bernd.edlinger at hotmail dot de
2013-07-26 8:16 ` ramana at gcc dot gnu.org
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