RFR: frame::describe: fix stack parameter location.

[Ron Pressler]

On Fri, 29 Apr 2022 17:37:09 GMT, Richard Reingruber <rrich at openjdk.org> wrote:

> Hi,
> 
> I'd like to contribute a small fix for a bug in `frame::describe()` I noticed while working on the ppc64le port.
> 
> Symptom: wrong location of stack parameters in compiled java calls on ppc64:
> 
> 
> [6.223s][trace][continuations ]  0x00007fffb53bd660: 0x00007fffb53bd830 #6 nmethod 0x00007fffa5026890 for method J BasicExpWIP$ContinuationCompiledFrameWithStackArgs.testMethod_12_dontinline(JJJJJJJJJJJJJ)J
> [6.223s][trace][continuations ]                                         - #0 scope BasicExpWIP$ContinuationCompiledFrameWithStackArgs.testMethod_12_dontinline(JJJJJJJJJJJJJ)J @ 28
> [6.223s][trace][continuations ]                                         param 7 long for #6
> [6.223s][trace][continuations ]                                         unextended_sp for #7
> [6.223s][trace][continuations ]                                         sp for #7
> [6.223s][trace][continuations ]  0x00007fffb53bd658: 0x00007fffa10077b0
> [6.223s][trace][continuations ]  0x00007fffb53bd650: 0x00007fffb53bd7c8
> [6.223s][trace][continuations ]  0x00007fffb53bd648: 0x00007fffb7c90c20
> [6.223s][trace][continuations ]  0x00007fffb53bd640: 0x000000000000000d
> [6.223s][trace][continuations ]  0x00007fffb53bd638: 0x000000000000000c
> [6.223s][trace][continuations ]  0x00007fffb53bd630: 0x000000000000000b
> [6.223s][trace][continuations ]  0x00007fffb53bd628: 0x000000000000000a
> [6.223s][trace][continuations ]  0x00007fffb53bd620: 0x0000000000000009 param 13 long for #5
> [6.223s][trace][continuations ]  0x00007fffb53bd618: 0x0000000000000008 param 12 long for #5
> [6.223s][trace][continuations ]  0x00007fffb53bd610: 0x0000000000000007 param 11 long for #5
> [6.223s][trace][continuations ]  0x00007fffb53bd608: 0x00007fffb53bd5c0 param 10 long for #5
> [6.224s][trace][continuations ]  0x00007fffb53bd600: 0x00007fffa5026ba8 param 9 long for #5
> [6.224s][trace][continuations ]                                         return address for #6
> [6.224s][trace][continuations ]  0x00007fffb53bd5f8: 0x00007fffa0e3a220 param 8 long for #5
> [6.224s][trace][continuations ]  0x00007fffb53bd5f0: 0x00007fffb53bd660 #5 nmethod 0x00007fffa5026190 for method J BasicExpWIP$ContinuationCompiledFrameWithStackArgs.testMethod_13_dontinline(JJJJJJJJJJJJJJ)J
> 
> 
> You can see that the locations of the stack parameters are wrong, because value for param N is (long)N.
> 
> Trace with the fix:
> 
> 
> [8.273s][trace][continuations ]  0x00007fffb53bd660: 0x00007fffb53bd830 #6 nmethod 0x00007fffa5026890 for method J BasicExpWIP$ContinuationCompiledFrameWithStackArgs.testMethod_12_dontinline(JJJJJJJJJJJJJ)J
> [8.273s][trace][continuations ]                                         - #0 scope BasicExpWIP$ContinuationCompiledFrameWithStackArgs.testMethod_12_dontinline(JJJJJJJJJJJJJ)J @ 28
> [8.273s][trace][continuations ]                                         unextended_sp for #7
> [8.273s][trace][continuations ]                                         sp for #7
> [8.273s][trace][continuations ]  0x00007fffb53bd658: 0x00007fffa10077b0
> [8.273s][trace][continuations ]  0x00007fffb53bd650: 0x00007fffb53bd7c8
> [8.273s][trace][continuations ]  0x00007fffb53bd648: 0x00007fffb7c90c20
> [8.273s][trace][continuations ]  0x00007fffb53bd640: 0x000000000000000d param 13 long for #5
> [8.273s][trace][continuations ]  0x00007fffb53bd638: 0x000000000000000c param 12 long for #5
> [8.273s][trace][continuations ]  0x00007fffb53bd630: 0x000000000000000b param 11 long for #5
> [8.273s][trace][continuations ]  0x00007fffb53bd628: 0x000000000000000a param 10 long for #5
> [8.273s][trace][continuations ]  0x00007fffb53bd620: 0x0000000000000009 param 9 long for #5
> [8.273s][trace][continuations ]  0x00007fffb53bd618: 0x0000000000000008 param 8 long for #5
> [8.273s][trace][continuations ]  0x00007fffb53bd610: 0x0000000000000007 param 7 long for #5
> [8.273s][trace][continuations ]  0x00007fffb53bd608: 0x00007fffb53bd5c0
> [8.273s][trace][continuations ]  0x00007fffb53bd600: 0x00007fffa5026ba8 return address for #6
> [8.273s][trace][continuations ]  0x00007fffb53bd5f8: 0x00007fffa0e3a220
> [8.273s][trace][continuations ]  0x00007fffb53bd5f0: 0x00007fffb53bd660 #5 nmethod 0x00007fffa5026190 for method J BasicExpWIP$ContinuationCompiledFrameWithStackArgs.testMethod_13_dontinline(JJJJJJJJJJJJJJ)J
> 
> 
> See also [`reg2offset()`](https://github.com/openjdk/jdk/blob/3d07b3c7f01b60ff4dc38f62407c212b48883dbf/src/hotspot/cpu/ppc/sharedRuntime_ppc.cpp#L573-L575)
> 
> I've done only manual testing.
> 
> The change has no effect on x86_64/aarch64 because there [`SharedRuntime::out_preserve_stack_slots()`](https://github.com/openjdk/jdk/blob/3d07b3c7f01b60ff4dc38f62407c212b48883dbf/src/hotspot/cpu/x86/sharedRuntime_x86_64.cpp#L2259-L2261) returns 0.
> 
> Thanks, Richard.

Marked as reviewed by rpressler (Lead).

This looks good, and I'd be happy to integrate it once we do some testing.
Thank you!

-------------

PR: https://git.openjdk.java.net/loom/pull/179