[PATCH] D75300: Support prefix padding for alignment purposes (Relaxable instructions only)

[Kan Shengchen via Phabricator via llvm-commits]

skan added a comment.

Encountered a compile error when building SPEC with option `-fno-lto -mllvm --x86-align-branch-boundary=32 -mllvm -x86-align-branch=fused+jcc+jmp -mllvm -x86-pad-max-prefix-size=5`.

  fatal error: error in backend: value of -130 is too large for field of 1 byte.

This error is reported when applying fixups

  void X86AsmBackend::applyFixup(const MCAssembler &Asm, const MCFixup &Fixup,
                                 const MCValue &Target,
                                 MutableArrayRef<char> Data,
                                 uint64_t Value, bool IsResolved,
                                 const MCSubtargetInfo *STI) const {
    unsigned Size = getFixupKindSize(Fixup.getKind());
  
    assert(Fixup.getOffset() + Size <= Data.size() && "Invalid fixup offset!");
  
    int64_t SignedValue = static_cast<int64_t>(Value);
    if ((Target.isAbsolute() || IsResolved) &&
        getFixupKindInfo(Fixup.getKind()).Flags &
        MCFixupKindInfo::FKF_IsPCRel) {
      // check that PC relative fixup fits into the fixup size.
      if (Size > 0 && !isIntN(Size * 8, SignedValue))
        Asm.getContext().reportError(
                                     Fixup.getLoc(), "value of " + Twine(SignedValue) +
                                     " is too large for field of " + Twine(Size) +
                                     ((Size == 1) ? " byte." : " bytes."));


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D75300/new/

https://reviews.llvm.org/D75300