Quelle c2_intelJccErratum_x86.cpp Sprache: C

/*
* Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/

#include "precompiled.hpp"
#include "asm/macroAssembler.hpp"
#include "c2_intelJccErratum_x86.hpp"
#include "opto/cfgnode.hpp"
#include "opto/compile.hpp"
#include "opto/machnode.hpp"
#include "opto/node.hpp"
#include "opto/output.hpp"
#include "opto/regalloc.hpp"
#include "utilities/align.hpp"
#include "utilities/debug.hpp"

// Compute which 32 byte boundary an address corresponds to
uintptr_t IntelJccErratum::boundary(uintptr_t addr) {
  return addr >> 5;
}

bool IntelJccErratum::is_crossing_or_ending_at_32_byte_boundary(uintptr_t start_pc, uintptr_t end_pc) {
  int jcc_size = int(end_pc - start_pc);
  assert(jcc_size <= largest_jcc_size(), "invalid jcc size: %d", jcc_size);
  return boundary(start_pc) != boundary(end_pc);
}

bool IntelJccErratum::is_jcc_erratum_branch(const MachNode* node) {
  if (node->is_MachCall() && !node->is_MachCallJava()) {
    return true;
  }
  return node->is_MachBranch();
}

int IntelJccErratum::jcc_erratum_taint_node(MachNode* node, PhaseRegAlloc* regalloc) {
  node->add_flag(Node::PD::Flag_intel_jcc_erratum);
  return node->size(regalloc);
}

int IntelJccErratum::tag_affected_machnodes(Compile* C, PhaseCFG* cfg, PhaseRegAlloc* regalloc) {
  ResourceMark rm;
  int nop_size = 0;
  MachNode* last_m = NULL;

  for (uint i = 0; i < cfg->number_of_blocks(); ++i) {
    const Block* const block = cfg->get_block(i);
    for (uint j = 0; j < block->number_of_nodes(); ++j) {
      const Node* const node = block->get_node(j);
      if (!node->is_Mach()) {
        continue;
      }
      MachNode* m = node->as_Mach();
      if (is_jcc_erratum_branch(m)) {
        // Found a root jcc erratum branch, flag it as problematic
        nop_size += jcc_erratum_taint_node(m, regalloc);

        if (!m->is_MachReturn() && !m->is_MachCall()) {
          // We might fuse a problematic jcc erratum branch with a preceding
          // ALU instruction - we must catch such problematic macro fusions
          // and flag the ALU instruction as problematic too.
          for (uint k = 1; k < m->req(); ++k) {
            const Node* const use = m->in(k);
            if (use == last_m && !m->is_MachReturn()) {
              // Flag fused conditions too
              nop_size += jcc_erratum_taint_node(last_m, regalloc);
            }
          }
        }
        last_m = NULL;
      } else {
        last_m = m;
      }
    }
  }
  return nop_size;
}

int IntelJccErratum::compute_padding(uintptr_t current_offset, const MachNode* mach, Block* block, uint index_in_block, PhaseRegAlloc* regalloc) {
  int jcc_size = mach->size(regalloc);
  if (index_in_block < block->number_of_nodes() - 1) {
    Node* next = block->get_node(index_in_block + 1);
    if (next->is_Mach() && (next->as_Mach()->flags() & Node::PD::Flag_intel_jcc_erratum)) {
      jcc_size += mach->size(regalloc);
    }
  }
  if (jcc_size > largest_jcc_size()) {
    // Let's not try fixing this for nodes that seem unreasonably large
    return false;
  }
  if (is_crossing_or_ending_at_32_byte_boundary(current_offset, current_offset + jcc_size)) {
    return int(align_up(current_offset, 32) - current_offset);
  } else {
    return 0;
  }
}

#define __ _masm.

uintptr_t IntelJccErratumAlignment::pc() {
  return (uintptr_t)__ pc();
}

IntelJccErratumAlignment::IntelJccErratumAlignment(MacroAssembler& masm, int jcc_size) :
    _masm(masm),
    _start_pc(pc()) {
  if (!VM_Version::has_intel_jcc_erratum()) {
    return;
  }

  if (Compile::current()->output()->in_scratch_emit_size()) {
    // When we measure the size of this 32 byte alignment, we apply a conservative guess.
    __ nop(jcc_size);
  } else if (IntelJccErratum::is_crossing_or_ending_at_32_byte_boundary(_start_pc, _start_pc + jcc_size)) {
    // The affected branch might get slowed down by micro code mitigations
    // as it could be susceptible to the erratum. Place nops until the next
    // 32 byte boundary to make sure the branch will be cached.
    const int alignment_nops = (int)(align_up(_start_pc, 32) - _start_pc);
    __ nop(alignment_nops);
    _start_pc = pc();
  }
}

IntelJccErratumAlignment::~IntelJccErratumAlignment() {
  if (!VM_Version::has_intel_jcc_erratum() ||
      Compile::current()->output()->in_scratch_emit_size()) {
    return;
  }

  assert(!IntelJccErratum::is_crossing_or_ending_at_32_byte_boundary(_start_pc, pc()), "Invalid jcc_size estimate");
}

quality95%

¤ Dauer der Verarbeitung: 0.12 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.