8358696: Assert with extreme values for -XX:BciProfileWidth

[sarannat]

Issue
Extreme values for BciProfileWidth flag such as java -XX:BciProfileWidth=-1 -version and java -XX:BciProfileWidth=100000 -version results in assert failure assert(allocates2(pc)) failed: not in CodeBuffer memory: 0x0000772b63a7a3a0 <= 0x0000772b63b75159 <= 0x0000772b63b75158

Analysis
The flag BciProfileWidth is used to specify the number of return BCI's to be recorded in the ret profile. On debugging the issue, I found that increasing the size of the interpreter using the InterpreterCodeSize in src/hotspot/cpu/x86/templateInterpreterGenerator_x86.cpp file prevented the above mentioned assert from failing for large values of BciProfileWidth. Additionally, a value below zero for BciProfileWidth implies that no return BCI's are to be recorded in the ret profile. This makes it equivalent to specifying the value zero.

Proposal
Considering the fact that larger BciProfileWidth results in slower profiling, I have proposed a range to restrict the value for BciProfileWidth that works for the current InterpreterCodeSize. The value ofInterpreterCodeSize is platform dependent. Hence, the upper bound of the range results from considering the lowest InterpreterCodeSize that does not result in a failure. However, I have only tested this on a x86 machine.

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Issue

• JDK-8358696: Assert with extreme values for -XX:BciProfileWidth (Bug - P4)

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[sarannat]

/cc hotspot-compiler

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