llvm-mirror/lib/MCA/CodeEmitter.cpp
Shengchen Kan 88597bc560 [MC][Bugfix] Remove redundant parameter for relaxInstruction
Summary:
Before this patch, `relaxInstruction` takes three arguments, the first
argument refers to the instruction before relaxation and the third
argument is the output instruction after relaxation. There are two quite
strange things:
  1) The first argument's type is `const MCInst &`, the third
  argument's type is `MCInst &`, but they may be aliased to the same
  variable
  2) The backends of ARM, AMDGPU, RISC-V, Hexagon assume that the third
  argument is a fresh uninitialized `MCInst` even if `relaxInstruction`
  may be called like `relaxInstruction(Relaxed, STI, Relaxed)` in a
  loop.

In this patch, we drop the thrid argument, and let `relaxInstruction`
directly modify the given instruction. Also, this patch fixes the bug https://bugs.llvm.org/show_bug.cgi?id=45580, which is introduced by D77851, and
breaks the assumption of ARM, AMDGPU, RISC-V, Hexagon.

Reviewers: Razer6, MaskRay, jyknight, asb, luismarques, enderby, rtaylor, colinl, bcain

Reviewed By: Razer6, MaskRay, bcain

Subscribers: bcain, nickdesaulniers, nathanchance, wuzish, annita.zhang, arsenm, dschuff, jyknight, dylanmckay, sdardis, nemanjai, jvesely, nhaehnle, tpr, sbc100, jgravelle-google, kristof.beyls, hiraditya, aheejin, kbarton, fedor.sergeev, asb, rbar, johnrusso, simoncook, sabuasal, niosHD, jrtc27, MaskRay, zzheng, edward-jones, atanasyan, rogfer01, MartinMosbeck, brucehoult, the_o, PkmX, jocewei, Jim, lenary, s.egerton, pzheng, sameer.abuasal, apazos, luismarques, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D78364
2020-04-21 11:06:55 +08:00

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//===--------------------- CodeEmitter.cpp ----------------------*- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file implements the CodeEmitter API.
//
//===----------------------------------------------------------------------===//
#include "llvm/MCA/CodeEmitter.h"
namespace llvm {
namespace mca {
CodeEmitter::EncodingInfo
CodeEmitter::getOrCreateEncodingInfo(unsigned MCID) {
EncodingInfo &EI = Encodings[MCID];
if (EI.second)
return EI;
SmallVector<llvm::MCFixup, 2> Fixups;
const MCInst &Inst = Sequence[MCID];
MCInst Relaxed(Sequence[MCID]);
if (MAB.mayNeedRelaxation(Inst, STI))
MAB.relaxInstruction(Relaxed, STI);
EI.first = Code.size();
MCE.encodeInstruction(Relaxed, VecOS, Fixups, STI);
EI.second = Code.size() - EI.first;
return EI;
}
} // namespace mca
} // namespace llvm