[all-commits] [llvm/llvm-project] 5e7183: [MC] Add MCSubtargetInfo to MCAlignFragment

Tue Sep 7 07:47:22 PDT 2021

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 5e71839f7793b3ab94e928654a493cb3d7216176
      https://github.com/llvm/llvm-project/commit/5e71839f7793b3ab94e928654a493cb3d7216176
  Author: Peter Smith <peter.smith at arm.com>
  Date:   2021-09-07 (Tue, 07 Sep 2021)

  Changed paths:
    M clang/tools/driver/cc1as_main.cpp
    M llvm/include/llvm/MC/MCELFStreamer.h
    M llvm/include/llvm/MC/MCFragment.h
    M llvm/include/llvm/MC/MCObjectStreamer.h
    M llvm/include/llvm/MC/MCStreamer.h
    M llvm/include/llvm/MC/MCWinCOFFStreamer.h
    M llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
    M llvm/lib/MC/ConstantPools.cpp
    M llvm/lib/MC/MCAsmStreamer.cpp
    M llvm/lib/MC/MCELFStreamer.cpp
    M llvm/lib/MC/MCObjectStreamer.cpp
    M llvm/lib/MC/MCParser/AsmParser.cpp
    M llvm/lib/MC/MCParser/MasmParser.cpp
    M llvm/lib/MC/MCStreamer.cpp
    M llvm/lib/MC/MCWinCOFFStreamer.cpp
    M llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
    M llvm/lib/Target/ARM/ARMAsmPrinter.cpp
    M llvm/lib/Target/ARM/ARMMCInstLower.cpp
    M llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
    M llvm/lib/Target/ARM/MCTargetDesc/ARMELFStreamer.cpp
    M llvm/lib/Target/Hexagon/AsmParser/HexagonAsmParser.cpp
    M llvm/lib/Target/Hexagon/HexagonAsmPrinter.cpp
    M llvm/lib/Target/Hexagon/HexagonTargetStreamer.h
    M llvm/lib/Target/Mips/MCTargetDesc/MipsTargetStreamer.cpp
    M llvm/lib/Target/Mips/MipsAsmPrinter.cpp
    M llvm/lib/Target/PowerPC/MCTargetDesc/PPCELFStreamer.cpp
    M llvm/lib/Target/PowerPC/MCTargetDesc/PPCXCOFFStreamer.cpp
    M llvm/lib/Target/PowerPC/PPCAsmPrinter.cpp
    M llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
    M llvm/lib/Target/X86/X86MCInstLower.cpp
    M llvm/tools/llvm-mc/Disassembler.cpp
    M llvm/tools/llvm-mc/llvm-mc.cpp
    M llvm/tools/llvm-ml/Disassembler.cpp
    M llvm/unittests/DebugInfo/DWARF/DWARFExpressionCopyBytesTest.cpp

  Log Message:
  -----------
  [MC] Add MCSubtargetInfo to MCAlignFragment

In preparation for passing the MCSubtargetInfo (STI) through to writeNops
so that it can use the STI in operation at the time, we need to record the
STI in operation when a MCAlignFragment may write nops as padding. The
STI is currently unused, a further patch will pass it through to
writeNops.

There are many places that can create an MCAlignFragment, in most cases
we can find out the STI in operation at the time. In a few places this
isn't possible as we are in initialisation or finalisation, or are
emitting constant pools. When possible I've tried to find the most
appropriate existing fragment to obtain the STI from, when none is
available use the per module STI.

For constant pools we don't actually need to use EmitCodeAlign as the
constant pools are data anyway so falling through into it via an
executable NOP is no better than falling through into data padding.

This is a prerequisite for D45962 which uses the STI to emit the
appropriate NOP for the STI. Which can differ per fragment.

Note that involves an interface change to InitSections. It is now
called initSections and requires a SubtargetInfo as a parameter.

Differential Revision: https://reviews.llvm.org/D45961

  Commit: e63455d5e0e5d148215a61c0e4d10f00aaf6eb56
      https://github.com/llvm/llvm-project/commit/e63455d5e0e5d148215a61c0e4d10f00aaf6eb56
  Author: Peter Smith <peter.smith at arm.com>
  Date:   2021-09-07 (Tue, 07 Sep 2021)

  Changed paths:
    M llvm/include/llvm/MC/MCAsmBackend.h
    M llvm/include/llvm/MC/MCFragment.h
    M llvm/include/llvm/MC/MCObjectStreamer.h
    M llvm/include/llvm/MC/MCStreamer.h
    M llvm/lib/MC/MCAssembler.cpp
    M llvm/lib/MC/MCObjectStreamer.cpp
    M llvm/lib/MC/MCStreamer.cpp
    M llvm/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
    M llvm/lib/Target/AMDGPU/MCTargetDesc/AMDGPUAsmBackend.cpp
    M llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
    M llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.h
    M llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendDarwin.h
    M llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendELF.h
    M llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackendWinCOFF.h
    M llvm/lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp
    M llvm/lib/Target/AVR/MCTargetDesc/AVRAsmBackend.h
    M llvm/lib/Target/BPF/MCTargetDesc/BPFAsmBackend.cpp
    M llvm/lib/Target/CSKY/MCTargetDesc/CSKYAsmBackend.cpp
    M llvm/lib/Target/CSKY/MCTargetDesc/CSKYAsmBackend.h
    M llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp
    M llvm/lib/Target/Lanai/MCTargetDesc/LanaiAsmBackend.cpp
    M llvm/lib/Target/M68k/MCTargetDesc/M68kAsmBackend.cpp
    M llvm/lib/Target/MSP430/MCTargetDesc/MSP430AsmBackend.cpp
    M llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.cpp
    M llvm/lib/Target/Mips/MCTargetDesc/MipsAsmBackend.h
    M llvm/lib/Target/PowerPC/MCTargetDesc/PPCAsmBackend.cpp
    M llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.cpp
    M llvm/lib/Target/RISCV/MCTargetDesc/RISCVAsmBackend.h
    M llvm/lib/Target/Sparc/MCTargetDesc/SparcAsmBackend.cpp
    M llvm/lib/Target/SystemZ/MCTargetDesc/SystemZMCAsmBackend.cpp
    M llvm/lib/Target/VE/MCTargetDesc/VEAsmBackend.cpp
    M llvm/lib/Target/WebAssembly/MCTargetDesc/WebAssemblyAsmBackend.cpp
    M llvm/lib/Target/X86/AsmParser/X86AsmParser.cpp
    M llvm/lib/Target/X86/MCTargetDesc/X86AsmBackend.cpp
    A llvm/test/CodeGen/ARM/subtarget-align.ll
    A llvm/test/MC/ARM/subtarget-nop.s
    M llvm/unittests/DebugInfo/DWARF/DWARFExpressionCopyBytesTest.cpp

  Log Message:
  -----------
  [MC] Use local MCSubtargetInfo in writeNops

On some architectures such as Arm and X86 the encoding for a nop may
change depending on the subtarget in operation at the time of
encoding. This change replaces the per module MCSubtargetInfo retained
by the targets AsmBackend in favour of passing through the local
MCSubtargetInfo in operation at the time.

On Arm using the architectural NOP instruction can have a performance
benefit on some implementations.

For Arm I've deleted the copy of the AsmBackend's MCSubtargetInfo to
limit the chances of this causing problems in the future. I've not
done this for other targets such as X86 as there is more frequent use
of the MCSubtargetInfo and it looks to be for stable properties that
we would not expect to vary per function.

This change required threading STI through MCNopsFragment and
MCBoundaryAlignFragment.

I've attempted to take into account the in tree experimental backends.

Differential Revision: https://reviews.llvm.org/D45962

Compare: https://github.com/llvm/llvm-project/compare/640beb38e771...e63455d5e0e5