[all-commits] [llvm/llvm-project] 5bd01a: [AArch64] Re-enable rematerialization for streamin...

[Sander de Smalen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5bd01ac822d1d700623790ef146fb78216576616
      https://github.com/llvm/llvm-project/commit/5bd01ac822d1d700623790ef146fb78216576616
  Author: Sander de Smalen <sander.desmalen at arm.com>
  Date:   2024-02-29 (Thu, 29 Feb 2024)

  Changed paths:
    M llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
    M llvm/lib/Target/AArch64/AArch64InstrFormats.td
    M llvm/lib/Target/AArch64/AArch64InstrInfo.cpp
    M llvm/lib/Target/AArch64/AArch64InstrInfo.h
    M llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp
    M llvm/lib/Target/AArch64/AArch64SMEInstrInfo.td
    M llvm/lib/Target/AArch64/SMEInstrFormats.td
    M llvm/lib/Target/AArch64/SVEInstrFormats.td
    M llvm/test/CodeGen/AArch64/debug-info-sve-dbg-declare.mir
    M llvm/test/CodeGen/AArch64/debug-info-sve-dbg-value.mir
    M llvm/test/CodeGen/AArch64/live-debugvalues-sve.mir
    M llvm/test/CodeGen/AArch64/sve-localstackalloc.mir
    M llvm/test/CodeGen/AArch64/sve-pfalse-machine-cse.mir
    M llvm/test/CodeGen/AArch64/sve-pseudos-expand-undef.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-cmpeq.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilege.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilegt.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilehi.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilehs.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilele.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilelo.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilels.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilelt.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilerw.mir
    M llvm/test/CodeGen/AArch64/sve-ptest-removal-whilewr.mir
    M llvm/test/CodeGen/AArch64/sve2p1_copy_pnr.mir

  Log Message:
  -----------
  [AArch64] Re-enable rematerialization for streaming-mode-changing functions. (#83235)

We can add implicit defs/uses of the 'VG' register to the instructions
to prevent the register allocator from rematerializing values in between
streaming-mode changes, as the def/use of VG will further nail down the
ordering that comes out of ISel. This avoids the heavy-handed approach
to prevent any kind of rematerialization.

While we could add 'VG' as a Use to all SVE instructions, we only really
need to do this for instructions that are rematerializable, as the
smstart/smstop instructions and pseudos act as scheduling barriers which
is sufficient to prevent other instructions from being scheduled in
between the streaming-mode-changing call sequence. However, we may
revisit this in the future.



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