Author: [EMAIL PROTECTED]
Date: Mon Sep 29 00:33:58 2008
New Revision: 393
Modified:
branches/bleeding_edge/src/assembler-ia32.cc
branches/bleeding_edge/src/assembler-ia32.h
Log:
Remove x86 jump elimination. This was just complicated enough to make it
annoying to support short jump encoding. I measured a code size increase
of 5 bytes on the V8 benchmark, from missing one jump to next elimination
possibility.
Modified: branches/bleeding_edge/src/assembler-ia32.cc
==============================================================================
--- branches/bleeding_edge/src/assembler-ia32.cc (original)
+++ branches/bleeding_edge/src/assembler-ia32.cc Mon Sep 29 00:33:58 2008
@@ -316,7 +316,6 @@
reloc_info_writer.Reposition(buffer_ + buffer_size, pc_);
last_pc_ = NULL;
- last_bound_pos_ = 0;
last_position_ = RelocInfo::kNoPosition;
last_statement_position_ = RelocInfo::kNoPosition;
}
@@ -335,9 +334,6 @@
void Assembler::GetCode(CodeDesc* desc) {
// finalize code
- if (unbound_label_.is_linked())
- bind_to(&unbound_label_, binding_pos_);
-
// (at this point overflow() may be true, but the gap ensures that
// we are still not overlapping instructions and relocation info)
ASSERT(pc_ <= reloc_info_writer.pos()); // no overlap
@@ -1229,10 +1225,6 @@
disp.next(L);
}
L->bind_to(pos);
-
- // do not eliminate jump instructions before the last bound position
- if (pos > last_bound_pos_)
- last_bound_pos_ = pos;
}
@@ -1266,49 +1258,6 @@
EnsureSpace ensure_space(this);
last_pc_ = NULL;
ASSERT(!L->is_bound()); // label can only be bound once
- if (FLAG_eliminate_jumps) {
- // Resolve unbound label.
- if (unbound_label_.is_linked()) {
- // Unbound label exists => link it with L if same binding
- // position, otherwise fix it.
- if (binding_pos_ == pc_offset()) {
- // Link it to L's list.
- link_to(L, &unbound_label_);
- } else {
- // Otherwise bind unbound label.
- ASSERT(binding_pos_ < pc_offset());
- bind_to(&unbound_label_, binding_pos_);
- }
- }
- ASSERT(!unbound_label_.is_linked());
- // try to eliminate jumps to next instruction
- const int absolute_jump_size = 5;
- // Do not remove an already bound jump target.
- while (last_bound_pos_ < pc_offset() &&
- reloc_info_writer.last_pc() <= pc_ - absolute_jump_size &&
- L->is_linked() &&
- (L->pos() + static_cast<int>(sizeof(int32_t)) == pc_offset()) &&
- (disp_at(L).type() == Displacement::UNCONDITIONAL_JUMP)) {
- // Previous instruction is jump jumping immediately after it =>
- // eliminate it.
- // jmp expected.
- ASSERT(byte_at(pc_offset() - absolute_jump_size) == 0xE9);
- if (FLAG_print_jump_elimination) {
- PrintF("@ %d jump to next eliminated\n", L->pos());
- }
- // Remove first entry from label list.
- Displacement disp = disp_at(L);
- disp.next(L);
- // Eliminate instruction (set code pointers back).
- pc_ -= absolute_jump_size;
- // Make sure not to skip relocation information when rewinding.
- ASSERT(reloc_info_writer.last_pc() <= pc_);
- }
- // Delay fixup of L => store it as unbound label.
- unbound_label_ = *L;
- binding_pos_ = pc_offset();
- L->Unuse();
- }
bind_to(L, pc_offset());
}
@@ -1376,16 +1325,6 @@
emit(offs - long_size);
}
} else {
- if (FLAG_eliminate_jumps &&
- unbound_label_.is_linked() &&
- binding_pos_ == pc_offset()) {
- // Current position is target of jumps
- if (FLAG_print_jump_elimination) {
- PrintF("eliminated jumps/calls to %d from ", binding_pos_);
- print(&unbound_label_);
- }
- link_to(L, &unbound_label_);
- }
// 1110 1001 #32-bit disp
EMIT(0xE9);
emit_disp(L, Displacement::UNCONDITIONAL_JUMP);
Modified: branches/bleeding_edge/src/assembler-ia32.h
==============================================================================
--- branches/bleeding_edge/src/assembler-ia32.h (original)
+++ branches/bleeding_edge/src/assembler-ia32.h Mon Sep 29 00:33:58 2008
@@ -727,14 +727,6 @@
// push-pop elimination
byte* last_pc_;
- // Jump-to-jump elimination:
- // The last label to be bound to _binding_pos, if unbound.
- Label unbound_label_;
- // The position to which _unbound_label has to be bound, if present.
- int binding_pos_;
- // The position before which jumps cannot be eliminated.
- int last_bound_pos_;
-
// source position information
int last_position_;
int last_statement_position_;
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