This commit addes pass to change CodeGen order to be bottom up order on Call Graph. The patch for the same has been provided by dear Mehdi Amini. This commit added required analysis passes for IPRA. 1) lib/CodeGen/RegUsageInfoCollector.cpp (MachineFunction Pass) to create RegMask based on actual register usage, scheduled at POST-RA 2) lib/CodeGen/RegisterUsageInfo.cpp (Immutable Pass) to store RegMask details for functions which has been processed in bottom up order on Call Graph, Scheduled before RegAllocation. This commit also adds a method setRegMask() to MachineOperand class. This commit also adds command line option to enable IPRA -enable-ipra and debug type "ip-regalloc". Changes to adher to coding standards, correction for ownership of RegMask vector in related functions.
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// This pass is required to take advantage of the interprocedural-register-allocation infrastructure.
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If you change from using a StringMap, update this comment.
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I'd also prefer a GlobalVariable * here, as that currently establishes our canonical function identify. If we work to further separate the MI level from the IR level, I suspect we'd establish some other function object which would have pointer-based identify, and we can always then update this code to use that instead.
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Since MatzeB commented about the allocation in std::vector in the MachineFunctionPass, it seems equally important to override doInitialization(Module &M) in order to reserve the size of the map with the number of functions defined in the module, and doFinalization to clear the map.
What is regMaskSize on ARM and X86?
I will consider it, do we required to revert those changes ? If yes then please suggest easy way, I am using git.
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Actually I run git clang-format , but that was after committing my changes so it did not changed any thing. I have applied clang-format on each file.
@qcolombet Could you please explain why is that required?
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oh yes this is already mentioned in coding standards but I really didn't check for it.
Isn't this will be called by method generated due to macroINITIALIZE_PASS_BEGIN ?
Have thought of any thing for this?
I believe CallGraphWrapperPass is required, though I have not look at this code closely as it was given by you :D
No these dependencies are not required, I am yet to find why not technically but I just removed it and compiled llvm again and things are working.
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I thought it is not for primitive type. I will change it.
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git clang-format takes a commit range, so you can format patches that are already committed.
If there is something in the macro expansion that makes you think it is called, please elaborate.
No, I look carefully at that macro it provides definition for initialize.. method but yes some where we need to call that method. Also I haven't mentioned this pass as dependency for any other pass with INITIALIZE_PASS_DEPENDENCY other wise it can call that function. Now I am also having same question as you.
Correction in typos , more adhering to coding standards.
PhysicalRegisterUsageInfo.cpp -> RegisterUsageInfo.cpp
DenseMap of GlobelVariable * to RegMask is used instead of StringMap.
DummyCGSCCPass moved to CallGraphSCCPass.h and .cpp
We're getting there, the patch is looking really good now! :)
Still a little bit of work ahead, see inline comments.
Describe the class with a doxygen comment.
Do not repeat the name of the function in the doxygen comment (other places that do it are outdated).
You shouldn't introduce implementation details in high-level description.
It is a good practice to decoupled software component. Having separate patches helps to make sure we indeed have correctly separated the components.
So I agree with Quentin on the principle, and I think it is also a good exercise for you to split the patch an submit the analysis alone and tested. Have a look at "CostModelAnalysis::print()" in lib/Analysis/CostModel.cpp and see how it is tested in test/Analysis/CostModel/X86/cast.ll
Why "compile time"? I'd just write "Enable inter-procedural register allocation"
You forgot to remove this hunk
@mehdi_amini I understand what you explain above but here I think RegisterUsageInfo is not tastable alone because it just holds RegMasks, RegisterInfoCollector is a trigger to IP regalloc and both of them can be tested together. Also to test X86RegUsageInfoPropagate it requires both of the above mentioned passes. But we can separate patches for RegisterUsageInfo + InfoCollector and X86RegUsageInfoPropagate ( condition that first patch is required to test second one) .
Just to make sure RegisterUsageInfo.cpp and RegUsageInfoCollector.cpp both are part of analysis so there is not need of separate patch for them but I will separate changes related to X86RegUsageInfoPropagate.cpp in other patch.
add a method print() like other analysis, and call it here behind a flag.
I don't like that we can't pass the test in release mode. I suggested that the dump occurs in doFinalization() for the analysis pass (i.e. PhysicalRegisterUsageInfo). You need to implement a proper cl::opt that controls a dump there, that could be used in release mode.
I'm worried that we don't provide any stability guarantee on the numbers printed here.
Technically in LLVM the analysis is the pass that you require and query the result from (i.e. a pass you're using as getAnalysis()). But yeah terminology can be fuzzy.
I think I already told you: the way analysis are tested at the IR level is using the -analyze flag in opt. Since we don't have -analyze in llc, the closest I can imagine is to implement the analysis (in the LLVM sense) with the "print(...)" method as other analyses, and call it in doFinalization() when a cl::opt flag is set.
Will TRI pointer assigned a value by the MachineFunction pass ? Or Is there any way to get TargetMachine or TargetRegisterInfo from Module object? Also if PReg name is required to be printed then MCRegisterInfo will be required.
Is the TRI dependent on the Target or the SubTarget?
I'm not sure the name of the option is great, but I'll leave the naming to Quentin/Matthias.
Can you implement the print in a separate print method with the same signature as the other analyses for consistency?
I tried out
but both returns nullptr for some functions.
My previous comment called out the fact that you were using an API for global *variables* instead of function, and you replaced with a call to getGlobalVariable?
There is a getFunction() API on the module that returns only functions, or there is a getNamedValue() that will return any symbol.
However you have MF.getFunction(), so you should not call any of these.
RegMasks uses Function * as key, print method and TargetMachine * have added to RegisterUsageInfo. Command line option -dump-regusage has been renamed to -print-regusage, test case is also updated to reflect the changes.
pair is not coding-convention friendly.
Also you are iterating on a map that is keyed on pointer values, which does not provided any ordering guarantee. Even with names as keys, the map is unordered anyway.
This test is not OK, for the reasons I explained when I provided the other test (stability).
I think MatzeB mentioned that TRI is a subclass of MCRI, so I'm not sure why you're using MCRI at all while you have TRI.
Why aren't you using MachineOperand::clobbersPhysReg here?
What will be printed for bar1 and bar2?
I was thinking about debug ability and usability of the produced code.
Something to consider in a following patch would be to add in the assembly output comments at the beginning of the function and/or related call site of the function listing what are the register preserved by the function.
The rationale is that now if we play with assembly files produced by different optimization phase, we want a quick way to check if two functions are equivalent.
Let say we have two assembly files produced for the same application:
- bad.s which fails, produced with ipra
- good.s which works, produced without ipra
When bisecting which function causes the failure, it is important to know if it is fine to take a function foo from good.s and replace it into bad.s. This may not be possible if the preserve register are not compatible.