Code cache and code cache manager #59
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This is a preparation for introducing `TRRuntime` and related classes that will also make use of target. So it is no longer just target for compilation.
This commit introduces a `TRRuntime`, a class that provides an entry point for runtime services. Downstream projects (if any) may (should) provide customized subclass. Note that "runtime" is only useful / used in JIT scenarios.
This commit adds new class - `TRCodeCache` - that implements simple runtime code cache to put compiled code (result of compilation) for later execution. Downstream project may need to provide customized implementations of code cache fitting the needs of particular runtime. `TRCodeCache` should serves (i) as example implementation, (ii) possibly as a base class for downstream projects and finally (iii) as code cache implementation to be used in tests. As of now, the implementation is fairly simple. Its functionality will be expanded in further commits.
This commit makes use of `TRCodeCache` introduced in previous commit. This is a necessary step for writing tests that compile multiple functions and/or refer to external (relocatable) symbols.
This commit extends test shell in two ways: * add another code section (`nzone2`) and two data sections (`heap1` and `heap2`). They're laid out in memory such that `nzone2` is further then 4GB from `nzone2`, similarly for data sections. This will allow testing of GOT / PLT based relocations on most platforms. Memory placement is done by linker script. * Add new variable `entry` whose value specifies the entrypoint of (injected) function (in either `nzone1` or `nzone2`. This is usefull when one wants to test complete program. Address of `entry` variable is fixed and again, specified by a linker script.
`TRCodeCacheManager` ties multiple code caches (here referred as 'segments') together. An (exported) symbol added to any of the segments is automatically made visible (and linked to) by all other segments managed by this manager. As with `TRCodeCache`, downstream project may need to provide customized implementations of code cache manager fitting the needs of particular runtime. This class serves example implementation and it is used in tests (see class `TRCompilationTestShell`) Downstream projects may also add new functionality such as automatically choosing the best segment to put new code object and/or invalidating/ flushing of code objects. As of now, the implementation is fairly simple. Its functionality may be expanded in further commits.
This commit makes use of `TRCodeCacheManager` in test shell, tying both nzones and heaps (introduced in commit "Extend test shell") together. This allows to test PIC code and relocation processing in various scenarios such as when relaxation is or is not possible and/or use of GOT/PLT entries.
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This PR adds
TRCodeCacheandTRCodeCacheManagerclasses.These serve as an example of how results of compilation (
AcDLSCodeObject) interacts with rest of execution environment (VM) and also as an implementation used by test shell.The shell itself has been extended to contain two code zones and two heaps, far apart of each other in address space to allow testing of relocations, GOT-based accesses, PLT calls and so on.