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hotspot/src/share/vm/asm/assembler.cpp

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+/*
+ * Copyright 1997-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+#include "incls/_precompiled.incl"
+#include "incls/_assembler.cpp.incl"
+
+
+// Implementation of AbstractAssembler
+//
+// The AbstractAssembler is generating code into a CodeBuffer. To make code generation faster,
+// the assembler keeps a copy of the code buffers boundaries & modifies them when
+// emitting bytes rather than using the code buffers accessor functions all the time.
+// The code buffer is updated via set_code_end(...) after emiting a whole instruction.
+
+AbstractAssembler::AbstractAssembler(CodeBuffer* code) {
+  if (code == NULL)  return;
+  CodeSection* cs = code->insts();
+  cs->clear_mark();   // new assembler kills old mark
+  _code_section = cs;
+  _code_begin  = cs->start();
+  _code_limit  = cs->limit();
+  _code_pos    = cs->end();
+  _oop_recorder= code->oop_recorder();
+  if (_code_begin == NULL)  {
+    vm_exit_out_of_memory1(0, "CodeCache: no room for %s", code->name());
+  }
+}
+
+void AbstractAssembler::set_code_section(CodeSection* cs) {
+  assert(cs->outer() == code_section()->outer(), "sanity");
+  assert(cs->is_allocated(), "need to pre-allocate this section");
+  cs->clear_mark();  // new assembly into this section kills old mark
+  _code_section = cs;
+  _code_begin  = cs->start();
+  _code_limit  = cs->limit();
+  _code_pos    = cs->end();
+}
+
+// Inform CodeBuffer that incoming code and relocation will be for stubs
+address AbstractAssembler::start_a_stub(int required_space) {
+  CodeBuffer*  cb = code();
+  CodeSection* cs = cb->stubs();
+  assert(_code_section == cb->insts(), "not in insts?");
+  sync();
+  if (cs->maybe_expand_to_ensure_remaining(required_space)
+      && cb->blob() == NULL) {
+    return NULL;
+  }
+  set_code_section(cs);
+  return pc();
+}
+
+// Inform CodeBuffer that incoming code and relocation will be code
+// Should not be called if start_a_stub() returned NULL
+void AbstractAssembler::end_a_stub() {
+  assert(_code_section == code()->stubs(), "not in stubs?");
+  sync();
+  set_code_section(code()->insts());
+}
+
+// Inform CodeBuffer that incoming code and relocation will be for stubs
+address AbstractAssembler::start_a_const(int required_space, int required_align) {
+  CodeBuffer*  cb = code();
+  CodeSection* cs = cb->consts();
+  assert(_code_section == cb->insts(), "not in insts?");
+  sync();
+  address end = cs->end();
+  int pad = -(intptr_t)end & (required_align-1);
+  if (cs->maybe_expand_to_ensure_remaining(pad + required_space)) {
+    if (cb->blob() == NULL)  return NULL;
+    end = cs->end();  // refresh pointer
+  }
+  if (pad > 0) {
+    while (--pad >= 0) { *end++ = 0; }
+    cs->set_end(end);
+  }
+  set_code_section(cs);
+  return end;
+}
+
+// Inform CodeBuffer that incoming code and relocation will be code
+// Should not be called if start_a_const() returned NULL
+void AbstractAssembler::end_a_const() {
+  assert(_code_section == code()->consts(), "not in consts?");
+  sync();
+  set_code_section(code()->insts());
+}
+
+
+void AbstractAssembler::flush() {
+  sync();
+  ICache::invalidate_range(addr_at(0), offset());
+}
+
+
+void AbstractAssembler::a_byte(int x) {
+  emit_byte(x);
+}
+
+
+void AbstractAssembler::a_long(jint x) {
+  emit_long(x);
+}
+
+// Labels refer to positions in the (to be) generated code.  There are bound
+// and unbound
+//
+// Bound labels refer to known positions in the already generated code.
+// offset() is the position the label refers to.
+//
+// Unbound labels refer to unknown positions in the code to be generated; it
+// may contain a list of unresolved displacements that refer to it
+#ifndef PRODUCT
+void AbstractAssembler::print(Label& L) {
+  if (L.is_bound()) {
+    tty->print_cr("bound label to %d|%d", L.loc_pos(), L.loc_sect());
+  } else if (L.is_unbound()) {
+    L.print_instructions((MacroAssembler*)this);
+  } else {
+    tty->print_cr("label in inconsistent state (loc = %d)", L.loc());
+  }
+}
+#endif // PRODUCT
+
+
+void AbstractAssembler::bind(Label& L) {
+  if (L.is_bound()) {
+    // Assembler can bind a label more than once to the same place.
+    guarantee(L.loc() == locator(), "attempt to redefine label");
+    return;
+  }
+  L.bind_loc(locator());
+  L.patch_instructions((MacroAssembler*)this);
+}
+
+void AbstractAssembler::generate_stack_overflow_check( int frame_size_in_bytes) {
+  if (UseStackBanging) {
+    // Each code entry causes one stack bang n pages down the stack where n
+    // is configurable by StackBangPages.  The setting depends on the maximum
+    // depth of VM call stack or native before going back into java code,
+    // since only java code can raise a stack overflow exception using the
+    // stack banging mechanism.  The VM and native code does not detect stack
+    // overflow.
+    // The code in JavaCalls::call() checks that there is at least n pages
+    // available, so all entry code needs to do is bang once for the end of
+    // this shadow zone.
+    // The entry code may need to bang additional pages if the framesize
+    // is greater than a page.
+
+    const int page_size = os::vm_page_size();
+    int bang_end = StackShadowPages*page_size;
+
+    // This is how far the previous frame's stack banging extended.
+    const int bang_end_safe = bang_end;
+
+    if (frame_size_in_bytes > page_size) {
+      bang_end += frame_size_in_bytes;
+    }
+
+    int bang_offset = bang_end_safe;
+    while (bang_offset <= bang_end) {
+      // Need at least one stack bang at end of shadow zone.
+      bang_stack_with_offset(bang_offset);
+      bang_offset += page_size;
+    }
+  } // end (UseStackBanging)
+}
+
+void Label::add_patch_at(CodeBuffer* cb, int branch_loc) {
+  assert(_loc == -1, "Label is unbound");
+  if (_patch_index < PatchCacheSize) {
+    _patches[_patch_index] = branch_loc;
+  } else {
+    if (_patch_overflow == NULL) {
+      _patch_overflow = cb->create_patch_overflow();
+    }
+    _patch_overflow->push(branch_loc);
+  }
+  ++_patch_index;
+}
+
+void Label::patch_instructions(MacroAssembler* masm) {
+  assert(is_bound(), "Label is bound");
+  CodeBuffer* cb = masm->code();
+  int target_sect = CodeBuffer::locator_sect(loc());
+  address target = cb->locator_address(loc());
+  while (_patch_index > 0) {
+    --_patch_index;
+    int branch_loc;
+    if (_patch_index >= PatchCacheSize) {
+      branch_loc = _patch_overflow->pop();
+    } else {
+      branch_loc = _patches[_patch_index];
+    }
+    int branch_sect = CodeBuffer::locator_sect(branch_loc);
+    address branch = cb->locator_address(branch_loc);
+    if (branch_sect == CodeBuffer::SECT_CONSTS) {
+      // The thing to patch is a constant word.
+      *(address*)branch = target;
+      continue;
+    }
+
+#ifdef ASSERT
+    // Cross-section branches only work if the
+    // intermediate section boundaries are frozen.
+    if (target_sect != branch_sect) {
+      for (int n = MIN2(target_sect, branch_sect),
+               nlimit = (target_sect + branch_sect) - n;
+           n < nlimit; n++) {
+        CodeSection* cs = cb->code_section(n);
+        assert(cs->is_frozen(), "cross-section branch needs stable offsets");
+      }
+    }
+#endif //ASSERT
+
+    // Push the target offset into the branch instruction.
+    masm->pd_patch_instruction(branch, target);
+  }
+}
+
+
+void AbstractAssembler::block_comment(const char* comment) {
+  if (sect() == CodeBuffer::SECT_INSTS) {
+    code_section()->outer()->block_comment(offset(), comment);
+  }
+}
+
+
+#ifndef PRODUCT
+void Label::print_instructions(MacroAssembler* masm) const {
+  CodeBuffer* cb = masm->code();
+  for (int i = 0; i < _patch_index; ++i) {
+    int branch_loc;
+    if (i >= PatchCacheSize) {
+      branch_loc = _patch_overflow->at(i - PatchCacheSize);
+    } else {
+      branch_loc = _patches[i];
+    }
+    int branch_pos  = CodeBuffer::locator_pos(branch_loc);
+    int branch_sect = CodeBuffer::locator_sect(branch_loc);
+    address branch = cb->locator_address(branch_loc);
+    tty->print_cr("unbound label");
+    tty->print("@ %d|%d ", branch_pos, branch_sect);
+    if (branch_sect == CodeBuffer::SECT_CONSTS) {
+      tty->print_cr(PTR_FORMAT, *(address*)branch);
+      continue;
+    }
+    masm->pd_print_patched_instruction(branch);
+    tty->cr();
+  }
+}
+#endif // ndef PRODUCT