Bug 88692 – DFG should be able to set watchpoints on global variables

• Component: JavaScriptCore
• Status: RESOLVED FIXED

[Filip Pizlo]

Work in progress patch on the way.

[Filip Pizlo]

Created attachment 146663 [details]
work in progress

[Filip Pizlo]

Created attachment 146684 [details]
more things

[Filip Pizlo]

Created attachment 146687 [details]
did some more stuff

Messed around with the interface between global variable creation, global variable access, and watch pointing.  It's starting to make sense.

Still more code to write, though.

[Filip Pizlo]

Created attachment 146716 [details]
even more

I just have to link together a few more things and it should start working.

[Filip Pizlo]

Created attachment 146721 [details]
more code

Still more stuff to do but it's getting there.

[Filip Pizlo]

Created attachment 146747 [details]
it might be done

Now I need to compile it.  And test it.

[Filip Pizlo]

Created attachment 146749 [details]
omg it compiles!

[Filip Pizlo]

Created attachment 146758 [details]
it does things

It looks like I can set a watchpoint on a global variable.  Note I said "set", not "fire".  I'm guessing it'll crash in hilarious ways if I actually try to fire a watchpoint.

[Filip Pizlo]

(In reply to comment #8)
> Created an attachment (id=146758) [details]
> it does things
> 
> It looks like I can set a watchpoint on a global variable.  Note I said "set", not "fire".  I'm guessing it'll crash in hilarious ways if I actually try to fire a watchpoint.

Actually, it can fire the watchpoints as well.  Fantastic!

Still have to do way more tests though.

[Filip Pizlo]

Created attachment 146996 [details]
the patch

[Geoffrey Garen]

Comment on attachment 146996 [details]
the patch

View in context: https://bugs.webkit.org/attachment.cgi?id=146996&action=review

r=me, please remember to ARM before landing.

> Source/JavaScriptCore/assembler/RepatchBuffer.h:125
> +    

Boo.

> Source/JavaScriptCore/assembler/X86Assembler.h:1737
> +        // FIXME: need to know the size of the last watchpoint as well.

No longer true.

> Source/JavaScriptCore/assembler/X86Assembler.h:1739
> +        while (UNLIKELY(static_cast<int>(result.m_offset) < m_indexOfTailOfLastWatchpoint)) {
> +            nop();

I think the ARMv7 code will also need to nop() pad in front of jumps, because of this case:

before jump relaxation:
watch_point
big jump
label:

after jump relaxation:
watch_point
small jump
label: [now inside the watchpoint]

> Source/JavaScriptCore/assembler/X86Assembler.h:1823
> +        int8_t *ptr = reinterpret_cast<int8_t*>(instructionStart);
> +        int8_t *dstPtr = reinterpret_cast<int8_t*>(to);
> +        intptr_t distance = (intptr_t)(dstPtr - (ptr + 5));

Move the "*", please.

[Filip Pizlo]

Created attachment 147154 [details]
rebased patch

Putting up for EWS.

[WebKit Review Bot]

Attachment 147154 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'Source/JavaScriptCore/CMakeLists.txt', u'S..." exit_code: 1
Source/JavaScriptCore/dfg/DFGOperations.h:103:  DFG_OPERATION is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/dfg/DFGOperations.h:120:  The parameter name "watchpointSet" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/runtime/SymbolTable.h:40:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/runtime/SymbolTable.h:69:  Should have only a single space after a punctuation in a comment.  [whitespace/comments] [5]
Source/WTF/wtf/SegmentedVector.h:37:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:805:  cmpb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:962:  testb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h:583:  The parameter name "constantMode" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h:583:  The parameter name "functionMode" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/bytecode/Watchpoint.h:52:  The parameter name "linkBuffer" adds no information, so it should be removed.  [readability/parameter_name] [5]
Total errors found: 10 in 62 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Build Bot]

Comment on attachment 147154 [details]
rebased patch

Attachment 147154 [details] did not pass mac-ews (mac):
Output: http://queues.webkit.org/results/12945666

[Build Bot]

Comment on attachment 147154 [details]
rebased patch

Attachment 147154 [details] did not pass win-ews (win):
Output: http://queues.webkit.org/results/12939819

[Filip Pizlo]

Created attachment 147193 [details]
the patch

Fixed Mac build issues.  I think.

[WebKit Review Bot]

Attachment 147193 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'Source/JavaScriptCore/CMakeLists.txt', u'S..." exit_code: 1
Source/JavaScriptCore/dfg/DFGOperations.h:103:  DFG_OPERATION is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/dfg/DFGOperations.h:120:  The parameter name "watchpointSet" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/runtime/SymbolTable.h:40:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/runtime/SymbolTable.h:69:  Should have only a single space after a punctuation in a comment.  [whitespace/comments] [5]
Source/WTF/wtf/SegmentedVector.h:37:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:805:  cmpb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:962:  testb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h:583:  The parameter name "constantMode" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h:583:  The parameter name "functionMode" adds no information, so it should be removed.  [readability/parameter_name] [5]
Total errors found: 9 in 60 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Build Bot]

Comment on attachment 147193 [details]
the patch

Attachment 147193 [details] did not pass win-ews (win):
Output: http://queues.webkit.org/results/12944699

[Build Bot]

Comment on attachment 147193 [details]
the patch

Attachment 147193 [details] did not pass mac-ews (mac):
Output: http://queues.webkit.org/results/12951098

[Early Warning System Bot]

Comment on attachment 147193 [details]
the patch

Attachment 147193 [details] did not pass qt-wk2-ews (qt):
Output: http://queues.webkit.org/results/12948609

[Early Warning System Bot]

Comment on attachment 147193 [details]
the patch

Attachment 147193 [details] did not pass qt-ews (qt):
Output: http://queues.webkit.org/results/12941797

[Filip Pizlo]

Created attachment 147207 [details]
backup

Still working on build systems, ports, crashes, etc.

[Filip Pizlo]

Created attachment 147235 [details]
real patch

Still doing more things but it's starting to work.

Unlike the previous patch, this one actually includes all of the files I've added!

[Filip Pizlo]

Created attachment 147238 [details]
ummmm please apply?

Rebased the patch in the hopes that the bots can apply it.

[WebKit Review Bot]

Attachment 147238 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'LayoutTests/ChangeLog', u'LayoutTests/fast..." exit_code: 1
Source/JavaScriptCore/dfg/DFGOperations.h:103:  DFG_OPERATION is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/dfg/DFGOperations.h:120:  The parameter name "watchpointSet" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/runtime/SymbolTable.h:40:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/runtime/SymbolTable.h:69:  Should have only a single space after a punctuation in a comment.  [whitespace/comments] [5]
Source/WTF/wtf/SegmentedVector.h:37:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:805:  cmpb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:962:  testb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h:583:  The parameter name "constantMode" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h:583:  The parameter name "functionMode" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/bytecode/Watchpoint.h:52:  The parameter name "linkBuffer" adds no information, so it should be removed.  [readability/parameter_name] [5]
Total errors found: 10 in 68 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Build Bot]

Comment on attachment 147238 [details]
ummmm please apply?

Attachment 147238 [details] did not pass win-ews (win):
Output: http://queues.webkit.org/results/12941861

[Filip Pizlo]

Created attachment 147245 [details]
attempting to fix Win

[WebKit Review Bot]

Attachment 147245 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'LayoutTests/ChangeLog', u'LayoutTests/fast..." exit_code: 1
Source/JavaScriptCore/dfg/DFGOperations.h:103:  DFG_OPERATION is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/dfg/DFGOperations.h:120:  The parameter name "watchpointSet" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/runtime/SymbolTable.h:40:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/runtime/SymbolTable.h:69:  Should have only a single space after a punctuation in a comment.  [whitespace/comments] [5]
Source/WTF/wtf/SegmentedVector.h:37:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:805:  cmpb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:962:  testb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 7 in 68 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Build Bot]

Comment on attachment 147245 [details]
attempting to fix Win

Attachment 147245 [details] did not pass win-ews (win):
Output: http://queues.webkit.org/results/12939939

[Filip Pizlo]

Created attachment 147252 [details]
attempt to fix the compiler's failed attempts to be smart

[WebKit Review Bot]

Attachment 147252 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'LayoutTests/ChangeLog', u'LayoutTests/fast..." exit_code: 1
Source/JavaScriptCore/dfg/DFGOperations.h:103:  DFG_OPERATION is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/dfg/DFGOperations.h:120:  The parameter name "watchpointSet" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/runtime/SymbolTable.h:40:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/runtime/SymbolTable.h:69:  Should have only a single space after a punctuation in a comment.  [whitespace/comments] [5]
Source/WTF/wtf/SegmentedVector.h:37:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:805:  cmpb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:962:  testb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 7 in 68 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Build Bot]

Comment on attachment 147252 [details]
attempt to fix the compiler's failed attempts to be smart

Attachment 147252 [details] did not pass win-ews (win):
Output: http://queues.webkit.org/results/12941882

[Filip Pizlo]

Created attachment 147255 [details]
fix link errors on Windows

[WebKit Review Bot]

Attachment 147255 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'LayoutTests/ChangeLog', u'LayoutTests/fast..." exit_code: 1
Source/JavaScriptCore/dfg/DFGOperations.h:103:  DFG_OPERATION is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/dfg/DFGOperations.h:120:  The parameter name "watchpointSet" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/runtime/SymbolTable.h:40:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/runtime/SymbolTable.h:69:  Should have only a single space after a punctuation in a comment.  [whitespace/comments] [5]
Source/WTF/wtf/SegmentedVector.h:37:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:805:  cmpb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:962:  testb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 7 in 69 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Filip Pizlo]

Landed in http://trac.webkit.org/changeset/120172

[Milian Wolff]

This commit breaks compilation on platforms where the ENALBE_JIT and hence ENABLE_ASSEMBLER is false (e.g. QNX).

The reason is that MacroAssembler::Label is used in Watchpoint.h, but the former is not defined on such platforms (see dummy definition at the end of MacroAssembler in MacroAssembler.h).

Should I create a new bug report for this?

[Filip Pizlo]

Created attachment 147393 [details]
more platform spoonfeeding

[WebKit Review Bot]

Attachment 147393 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'LayoutTests/ChangeLog', u'LayoutTests/fast..." exit_code: 1
Source/JavaScriptCore/dfg/DFGOperations.h:103:  DFG_OPERATION is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/dfg/DFGOperations.h:120:  The parameter name "watchpointSet" adds no information, so it should be removed.  [readability/parameter_name] [5]
Source/JavaScriptCore/runtime/SymbolTable.h:40:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/JavaScriptCore/runtime/SymbolTable.h:69:  Should have only a single space after a punctuation in a comment.  [whitespace/comments] [5]
Source/WTF/wtf/SegmentedVector.h:37:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Source/WTF/wtf/Assertions.h:386:  UNREACHABLE_FOR_PLATFORM is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:805:  cmpb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Source/JavaScriptCore/assembler/X86Assembler.h:962:  testb_im is incorrectly named. Don't use underscores in your identifier names.  [readability/naming] [4]
Total errors found: 8 in 72 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Filip Pizlo]

Relanded in http://trac.webkit.org/changeset/120244