Handle 8-byte call in VPIC snippet for nestmates #3005
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When x86 PicBuilder is carrying out a direct call to a private method of
a nestmate, it sets the return address so that the call will return into
the code in the VPIC snippet, which in the case of a virtual dispatch
would be something like the following:
call qword ptr [$vftReg+$vftOffset]
jmp mainline
In particular, the callee should return to the jmp instruction, whose
address has been calculated as 7 + the address of the call instruction.
But the call is sometimes one byte longer. The variability is now dealt
with as follows:
- When overwriting the call, PicBuilder now writes a value that works
for both 7- and 8-byte offsets to the jmp instruction.
- When doing direct dispatch for nestmates, PicBuilder now detects the
offset to jmp, in order to compute the correct return address.
Fixes eclipse-openj9#2955
Signed-off-by: Devin Papineau <devinmp@ca.ibm.com>
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Jenkins test sanity jdk11 xlinux,win |
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Jenkins test sanity xlinux,win jdk11 |
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@andrewcraik, is this good now? |
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When x86 PicBuilder is carrying out a direct call to a private method of
a nestmate, it sets the return address so that the call will return into
the code in the VPIC snippet, which in the case of a virtual dispatch
would be something like the following:
In particular, the callee should return to the jmp instruction, whose
address has been calculated as 7 + the address of the call instruction.
But the call is sometimes one byte longer. The variability is now dealt
with as follows:
When overwriting the call, PicBuilder now writes a value that works
for both 7- and 8-byte offsets to the jmp instruction.
When doing direct dispatch for nestmates, PicBuilder now detects the
offset to jmp, in order to compute the correct return address.
Fixes #2955