=> (EXTRWconst [32-c] x2 x)
(XORshiftLL <t> [c] (UBFX [bfc] x) x2) && c < 32 && t.Size() == 4 && bfc == armBFAuxInt(32-c, c)
	=> (EXTRWconst [32-c] x2 x)

// Rewrite special pairs of shifts to AND.
// On ARM64 the bitmask can fit into an instruction.
(SRLconst [c] (SLLconst [c] x)) && 0 < c && c < 64 => (ANDconst [1<<uint(64-c)-1] x) // mask out high bits

//	-race
//		enable data race detection.
//		Supported only on linux/amd64, freebsd/amd64, darwin/amd64, darwin/arm64, windows/amd64,
//		linux/ppc64le and linux/arm64 (only for 48-bit VMA).
//	-msan
//		enable interoperation with memory sanitizer.
//		Supported only on linux/amd64, linux/arm64, linux/loong64, freebsd/amd64
//		and only with Clang/LLVM as the host C compiler.

	if ctxt.Retpoline {
		ctxt.Diag("-spectre=ret not supported on arm64")
		ctxt.Retpoline = false // don't keep printing
	}

	p := cursym.Func().Text
	if p == nil || p.Link == nil { // handle external functions and ELF section symbols
		return
	}

	if oprange[AAND&obj.AMask] == nil {
		ctxt.Diag("arm64 ops not initialized, call arm64.buildop first")
	}

		if r.Type().IsDirectCallOrJump() {
			n++
		}
	}

	switch {
	case ctxt.IsARM():
		return n * 20 // Trampolines in ARM range from 3 to 5 instructions.
	case ctxt.IsARM64():
		return n * 12 // Trampolines in ARM64 are 3 instructions.
	case ctxt.IsPPC64():
		return n * 16 // Trampolines in PPC64 are 4 instructions.
	case ctxt.IsRISCV64():
		return n * 8 // Trampolines in RISCV64 are 2 instructions.
	}
	panic("unreachable")
}

  case "${HOST_ARCH}" in
    x86_64*|i?86_64*|amd64*)
      HOST_ARCH="amd64"
      ;;
    aHOST_arch64*|aarch64*|arm64*)
      HOST_ARCH="arm64"
      ;;
    *)
      echo "Unknown, unsupported architecture (${HOST_ARCH})." >&2
      echo "Supported architecture(s): amd64 and arm64." >&2
      echo "Bailing out." >&2
      exit 2
      ;;
  esac
}

	case "386", "amd64":
		x86HasPOPCNT = cpu.X86.HasPOPCNT
		x86HasSSE41 = cpu.X86.HasSSE41
		x86HasFMA = cpu.X86.HasFMA

	case "arm":
		armHasVFPv4 = cpu.ARM.HasVFPv4

	case "arm64":
		arm64HasATOMICS = cpu.ARM64.HasATOMICS
	}
}

// getGodebugEarly extracts the environment variable GODEBUG from the environment on
// Unix-like operating systems and returns it. This function exists to extract GODEBUG

	case "386":
		return []string{"-m32"}
	case "amd64":
		if cfg.Goos == "darwin" {
			return []string{"-arch", "x86_64", "-m64"}
		}
		return []string{"-m64"}
	case "arm64":
		if cfg.Goos == "darwin" {
			return []string{"-arch", "arm64"}
		}
	case "arm":
		return []string{"-marm"} // not thumb
	case "s390x":
		return []string{"-m64", "-march=z196"}
	case "mips64", "mips64le":

func (i R_X86_64) String() string   { return stringName(uint32(i), rx86_64Strings, false) }
func (i R_X86_64) GoString() string { return stringName(uint32(i), rx86_64Strings, true) }

// Relocation types for AArch64 (aka arm64)
type R_AARCH64 int

const (
	R_AARCH64_NONE                            R_AARCH64 = 0
	R_AARCH64_P32_ABS32                       R_AARCH64 = 1
	R_AARCH64_P32_ABS16                       R_AARCH64 = 2