llvm dev - Sep 2017 - Assertion in 'DwarfDebug.cpp'

Since updating to the LLVM v5.0 Final tag, I am seeing a crash when I enable
'-g'.  With a Debug build this hits an assertion at line #923 in
'lib/CodeGen/AsmPrinter/DwarfDebug.cpp':

assert(EndLabel && "Forgot label after instruction ending a
range!");

 

The values of related variables at this time are:

'Begin' is:      DBG_VALUE %I23, %noreg, !"fp", <!345>;
line no:381

'End' is:        DBG_VALUE %I19, 88, !"ap", <!345>; line
no:381 indirect

'StartLabel' is: .Ltmp327

 

'I19' is the stack-pointer, and it is the expression 'EndLabel
getLabelAfterInsn(End)' that is returning 'nullptr'.  This happens
only when
compiling 'vfprintf.c' or 'vfwprintf.c' from Newlib v2.5.0, and
line #381
referenced is the location of the declaration of the function
'_vfwprintf_r'.  But our implementation does not directly do anything
with
Dwarf meta-data, so I don't understand what we could be doing that would
cause this.

 

Has this been seen before, and any suggestions on how I should debug this?

 

Thanks,

 

            MartinO

 

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Here are a couple things I would try to help triangulate on the problem.

Try a vanilla upstream compiler for an in-tree target. (IIRC you have your own
target.)  If that fails, it's pretty optimal for you because you should be
able to reduce a test case and file a PR.  If it doesn't fail, that suggests
it's either something your target does or doesn't do, or some bug in how
you've done your adaptation to LLVM 5.0.

You can also try compiling with -S and assembling the result; I have seen that
behave differently from direct object generation sometimes.  If that's the
case here, it should be not terribly hard to work out how the paths are
different.

Good luck,
--paulr

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Martin
J. O'Riordan via llvm-dev
Sent: Monday, September 25, 2017 7:56 AM
To: 'LLVM Developers'
Subject: [llvm-dev] Assertion in 'DwarfDebug.cpp'

Since updating to the LLVM v5.0 Final tag, I am seeing a crash when I enable
'-g'.  With a Debug build this hits an assertion at line #923 in
'lib/CodeGen/AsmPrinter/DwarfDebug.cpp':
assert(EndLabel && "Forgot label after instruction ending a
range!");

The values of related variables at this time are:

'Begin' is:      DBG_VALUE %I23, %noreg, !"fp", <!345>;
line no:381

'End' is:        DBG_VALUE %I19, 88, !"ap", <!345>; line
no:381 indirect

'StartLabel' is: .Ltmp327

'I19' is the stack-pointer, and it is the expression 'EndLabel =
getLabelAfterInsn(End)' that is returning 'nullptr'.  This happens
only when compiling 'vfprintf.c' or 'vfwprintf.c' from Newlib
v2.5.0, and line #381 referenced is the location of the declaration of the
function '_vfwprintf_r'.  But our implementation does not directly do
anything with Dwarf meta-data, so I don't understand what we could be doing
that would cause this.

Has this been seen before, and any suggestions on how I should debug this?

Thanks,

            MartinO

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Thanks Paul,

 

Actually in my case (out of tree) I always compile to assembly.  It does
appear to crash only when my target is selected, I build the compiler with
multiple targets enabled, and it does not crash for the other in-tree
targets even with the same compiler binary.  Strange, I can't think of
anywhere in my target that handle debug information explicitly.

 

Have to roll my sleeves up and go hunting ;-)

 

            MartinO

 

From: Robinson, Paul [mailto:paul.robinson at sony.com] 
Sent: 25 September 2017 18:44
To: Martin J. O'Riordan <MartinO at theheart.ie>
Cc: llvm-dev at lists.llvm.org
Subject: RE: [llvm-dev] Assertion in 'DwarfDebug.cpp'

 

Here are a couple things I would try to help triangulate on the problem.

 

Try a vanilla upstream compiler for an in-tree target. (IIRC you have your
own target.)  If that fails, it's pretty optimal for you because you should
be able to reduce a test case and file a PR.  If it doesn't fail, that
suggests it's either something your target does or doesn't do, or some
bug
in how you've done your adaptation to LLVM 5.0.

 

You can also try compiling with -S and assembling the result; I have seen
that behave differently from direct object generation sometimes.  If that's
the case here, it should be not terribly hard to work out how the paths are
different.

 

Good luck,

--paulr

 

From: llvm-dev [mailto:llvm-dev-bounces at lists.llvm.org] On Behalf Of Martin
J. O'Riordan via llvm-dev
Sent: Monday, September 25, 2017 7:56 AM
To: 'LLVM Developers'
Subject: [llvm-dev] Assertion in 'DwarfDebug.cpp'

 

Since updating to the LLVM v5.0 Final tag, I am seeing a crash when I enable
'-g'.  With a Debug build this hits an assertion at line #923 in
'lib/CodeGen/AsmPrinter/DwarfDebug.cpp':

assert(EndLabel && "Forgot label after instruction ending a
range!");

 

The values of related variables at this time are:

'Begin' is:      DBG_VALUE %I23, %noreg, !"fp", <!345>;
line no:381

'End' is:        DBG_VALUE %I19, 88, !"ap", <!345>; line
no:381 indirect

'StartLabel' is: .Ltmp327

 

'I19' is the stack-pointer, and it is the expression 'EndLabel
getLabelAfterInsn(End)' that is returning 'nullptr'.  This happens
only when
compiling 'vfprintf.c' or 'vfwprintf.c' from Newlib v2.5.0, and
line #381
referenced is the location of the declaration of the function
'_vfwprintf_r'.  But our implementation does not directly do anything
with
Dwarf meta-data, so I don't understand what we could be doing that would
cause this.

 

Has this been seen before, and any suggestions on how I should debug this?

 

Thanks,

 

            MartinO

 

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