[llvm-dev] Function register clobber propagation

[Jason Eckhardt via llvm-dev]

There is at least some minimal support for this, see CodeGen/RegUsageInfoPropagate.cpp (and related). This interprocedural register allocation is enabled with "-enable-ipra".
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From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of Colin McEwan via llvm-dev <llvm-dev at lists.llvm.org>
Sent: Tuesday, November 30, 2021 9:26 AM
To: llvm-dev at lists.llvm.org <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] Function register clobber propagation

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Hi all,



Does LLVM currently have any way to exploit known register usage of already-compiled callee functions within a module to reduce register pressure in calling functions? GCC does this, but I haven’t seen any sign of this being done (having checked on a couple of different target architectures), and can’t find any mention of such optimisation in the source.



Have I overlooked something? Or is there a rationale for not attempting this? (Such as limiting potential parallelism in compiling a module)



Thanks!



--

Colin

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