efriedma added inline comments.
================
Comment at: llvm/lib/Target/AArch64/SVEInstrFormats.td:5333
+ // We need a layer of indirection because early machine code passes balk at
+ // physical register (i.e. FFR) uses that have no previous definition.
+ let hasSideEffects = 1, hasNoSchedulingInfo = 1, mayLoad = 1 in {
----------------
This is depending on hasSideEffects to preserve the correct ordering with
instructions that read/write FFR? That probably works. I guess the
alternative is to insert an IMPLICIT_DEF of FFR in the entry block of each
function.
What are the calling convention rules for FFR? Is it callee-save? If not, we
might need to do some work to make FFR reads/writes do something sane across
calls inserted by the compiler.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D71698/new/
https://reviews.llvm.org/D71698
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