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

[Richard Reingruber]

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.

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

Commit messages:
 - frame::describe: fix stack parameter location.

Changes: https://git.openjdk.java.net/loom/pull/179/files
 Webrev: https://webrevs.openjdk.java.net/?repo=loom&pr=179&range=00
  Stats: 4 lines in 1 file changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/loom/pull/179.diff
  Fetch: git fetch https://git.openjdk.java.net/loom pull/179/head:pull/179

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