[llvm-dev] LLVM Virtual registers after RA pass?

Arsenault, Matthew via llvm-dev llvm-dev at lists.llvm.org
Fri May 3 10:55:53 PDT 2019

There are a number of hooks to control this in PrologEpilogInserter spread between TargetFrameLowering and TargetRegisterInfo. The one you most want to look at is probably TargetRegisterInfo::requiresFrameIndexScavenging.


From: llvm-dev <llvm-dev-bounces at lists.llvm.org> on behalf of llvm-dev <llvm-dev at lists.llvm.org>
Reply-To: Joan Lluch <joan.lluch at icloud.com>
Date: Friday, May 3, 2019 at 7:50 PM
To: llvm-dev <llvm-dev at lists.llvm.org>
Subject: [llvm-dev] LLVM Virtual registers after RA pass?

I need to use ‘createVirtualRegister’ for a specific case in my ‘eliminateFrameIndex’ function implementation.

However, whenever that code is executed, I get the assertion "MachineCopyPropagation should be run after register allocation!” at a later stage.

I have seen that at least a couple of backend implementations (including ARM Thumb) create virtual registers in ‘eliminatedFrameIndex’.

What am I missing?, is there something that I need to set for virtual registers to be allowed after the RA pass, and specifically in the ‘eliminateFrameIndex’ function?


Joan Lluch
Puigsacalm, 7
17458 - Fornells de la Selva

Tel: 620 28 45 13

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