[clang] [lld] [llvm] [X86] Implement disabling APX relocations and EPGR/NDD instrs for relocations (PR #136660)

[Feng Zou via cfe-commits]

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+//===- X86SuppressAPXForReloc.cpp - Suppress APX features for relocations -===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+/// \file
+///
+/// This pass is added to suppress APX features for relocations. It's used
+/// together with disabling emitting APX relocation types for backward
+/// compatibility with old version of linker (like before LD 2.43). It can avoid
+/// the instructions updated incorrectly by old version of linker if the
+/// instructions are with APX EGPR/NDD/NF features + the relocations other than
+/// APX ones (like GOTTPOFF).
+///
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/X86BaseInfo.h"
+#include "MCTargetDesc/X86MCTargetDesc.h"
+#include "X86.h"
+#include "X86RegisterInfo.h"
+#include "X86Subtarget.h"
+
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/Target/TargetMachine.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "x86-suppress-apx-for-relocation"
+
+static cl::opt<bool> X86EnableAPXForRelocation(
+    "x86-enable-apx-for-relocation",
+    cl::desc("Enable APX features (EGPR, NDD and NF) for instructions with "
+             "relocations on x86-64 ELF"),
+    cl::init(false));
+
+namespace {
+class X86SuppressAPXForRelocationPass : public MachineFunctionPass {
+public:
+  X86SuppressAPXForRelocationPass() : MachineFunctionPass(ID) {}
+
+  StringRef getPassName() const override {
+    return "X86 Suppress APX features for relocation";
+  }
+
+  bool runOnMachineFunction(MachineFunction &MF) override;
+
+  static char ID;
+};
+} // namespace
+
+char X86SuppressAPXForRelocationPass::ID = 0;
+
+INITIALIZE_PASS_BEGIN(X86SuppressAPXForRelocationPass, DEBUG_TYPE,
+                      "X86 Suppress APX features for relocation", false, false)
+INITIALIZE_PASS_END(X86SuppressAPXForRelocationPass, DEBUG_TYPE,
+                    "X86 Suppress APX features for relocation", false, false)
+
+FunctionPass *llvm::createX86SuppressAPXForRelocationPass() {
+  return new X86SuppressAPXForRelocationPass();
+}
+
+static void suppressEGPRRegClass(MachineFunction &MF, MachineInstr &MI,
+                                 unsigned int OpNum) {
+  MachineRegisterInfo *MRI = &MF.getRegInfo();
+  auto Reg = MI.getOperand(OpNum).getReg();
+  if (!Reg.isVirtual()) {
+    assert(!X86II::isApxExtendedReg(Reg) && "APX EGPR is used unexpectedly.");
+    return;
+  }
+
+  auto *RC = MRI->getRegClass(Reg);
+  auto *NewRC = X86II::constrainRegClassToNonRex2(RC);
+  MRI->setRegClass(Reg, NewRC);
+}
+
+bool X86SuppressAPXForRelocationPass::runOnMachineFunction(
+    MachineFunction &MF) {
+  if (MF.getTarget().Options.MCOptions.X86APXRelaxRelocations ||
+      X86EnableAPXForRelocation)
+    return false;
+  const X86Subtarget &ST = MF.getSubtarget<X86Subtarget>();
+  if (!ST.hasEGPR() && !ST.hasNDD() && !ST.hasNF())
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fzou1 wrote:

There are NF instructions for GOT_6_GOTTPOFF.

https://github.com/llvm/llvm-project/pull/136660