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Hi David,<br>
<br>
It doesn't reproduce on X86 due to the differences in emitPrologue
for ARM and X86. While ARMFrameLowering::emitPrologue initializes
debug location:<br>
DebugLoc dl = MBBI != MBB.end() ? MBBI->getDebugLoc() :
DebugLoc();<br>
X86FrameLowering::emitPrologue leaves its default value:<br>
DebugLoc DL;<br>
ARMFrameLowering::emitPushInst has the same problem. <br>
Leaving it unitialized looks like a hack. <br>
<br>
Taking this into account, could you review if the r188651 patch is
fully correct, please?<br>
<br>
Thanks.<br>
<br>
<div class="moz-cite-prefix">25.06.2015 15:47, Oleg Ranevskyy пишет:<br>
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<div class="gmail_quote">On Wed, Jun 24, 2015 at 2:28 PM,
Oleg Ranevskyy <span dir="ltr"><<a
moz-do-not-send="true"
href="mailto:llvm.mail.list@gmail.com" target="_blank">llvm.mail.list@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
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<div bgcolor="#FFFFFF" text="#000000"> Hi David,<br>
<br>
I got a problem related to the change made in r188651
- not including file/line info for artificial
arguments like "this" and "self".<br>
Would you be able to take a look at it, please?<br>
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<div>Could you provide a simple test case? (& ideally:
does this reproduce on X86, a platform I've easy access
to (& if it doesn't, I'd be curious to understand
why not...))</div>
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Sure. It's enough to have a simple class with a constructor and
create its instance. <br>
Compile it w/o fast ISel, e.g.: clang -g -O0 main.cpp
--target=armv7l-unknown-linux-gnueabihf -mllvm -fast-isel=0<br>
<br>
class MyClass<br>
{<br>
public:<br>
MyClass()<br>
{<br>
}<br>
};<br>
int main()<br>
{<br>
MyClass obj; // <-- can't step into MyClass::MyClass()
here<br>
return 0;<br>
}<br>
<br>
It didn't reproduce on X86_64 though. I will try to find out why.<br>
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cite="mid:CAENS6EtFhJBcoNizfyD-41-hXL_A-OyYQssSvQOp-xwtj+ywmw@mail.gmail.com"
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<div bgcolor="#FFFFFF" text="#000000">I am compiling the
code for ARM linux with fast ISel disabled: -mllvm
-fast-isel=0. The problem is that it's not possible to
step into<span></span> the constructor, destructor or
a method of a class while debugging. Clang generates
correct .loc in function prologues, but then, due to
r188651, inserts a debug info location with zeroed
line number (.loc 1 0 0) for "this", which misleads
the debugger. <br>
<br>
Could you explain the reasoning behind this change,
please?<br>
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The reason for the change, if I recall correctly
(perhaps I mentioned in the commit message, I'm not
sure) was to reduce debug info size for the debug_info
section - I don't believe the intent was to have any
impact on the line table.<br>
<br>
(artificial variables, like "this" don't have a location
they are declared on, so there was/is no need to have a
DW_AT_decl_file/line in the debug_info describing their
declaration location)<br>
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I see, thanks.<br>
The r188651 patch leads to inserting ".loc 1 0 0" into the
constructor's code. Here is a part of the assembly I get for the
MyClass constructor:<br>
<br>
_ZN7MyClassC2Ev: @ @_ZN7MyClassC2Ev<br>
.Lfunc_begin1:<br>
.loc 1 7 0 @ main.cpp:7:0<br>
.fnstart<br>
.cfi_startproc<br>
@ BB#0: @ %entry<br>
.loc 1 0 0 @ main.cpp:0:0
<-------------- loc with line == 0 confuses the debugger<br>
.pad #4<br>
sub sp, sp, #4<br>
....<br>
<br>
Fast ISel removes this ".loc 1 0 0", so the debugger
successfully steps into the constructor due to the previous
".loc 1 7 0".<br>
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<div bgcolor="#FFFFFF" text="#000000"> <br>
This hasn't been noticed before due to the fast ISel
omitting location info for arguments, so the correct
location from the prologue is used. It is probably yet
another problem to handle.<br>
<br>
Thanks in advance for any help.<br>
Kind regards,<br>
Oleg<br>
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