Reviewers: Kevin Millikin, Description: Simplify the check when to perform loop invariant code motion.
Allow HChange instructions to be hoisted out of loops. To avoid unnecessary code motion we don't hoist instructions from blocks that have been marked containing an unconditional deoptimization. Please review this at http://codereview.chromium.org/7003087/ SVN Base: http://v8.googlecode.com/svn/branches/bleeding_edge/ Affected files: M src/flag-definitions.h M src/hydrogen.h M src/hydrogen.cc Index: src/flag-definitions.h =================================================================== --- src/flag-definitions.h (revision 8241) +++ src/flag-definitions.h (working copy) @@ -137,8 +137,6 @@ DEFINE_bool(trap_on_deopt, false, "put a break point before deoptimizing") DEFINE_bool(deoptimize_uncommon_cases, true, "deoptimize uncommon cases") DEFINE_bool(polymorphic_inlining, true, "polymorphic inlining") -DEFINE_bool(aggressive_loop_invariant_motion, true, - "aggressive motion of instructions out of loops") DEFINE_bool(use_osr, true, "use on-stack replacement") DEFINE_bool(trace_osr, false, "trace on-stack replacement") Index: src/hydrogen.cc =================================================================== --- src/hydrogen.cc (revision 8241) +++ src/hydrogen.cc (working copy) @@ -68,7 +68,8 @@ last_instruction_index_(-1), deleted_phis_(4), parent_loop_header_(NULL), - is_inline_return_target_(false) { } + is_inline_return_target_(false), + is_deoptimizing_(false) { } void HBasicBlock::AttachLoopInformation() { @@ -1449,35 +1450,9 @@ HBasicBlock* loop_header) { // If we've disabled code motion, don't move any instructions. if (!AllowCodeMotion()) return false; - - // If --aggressive-loop-invariant-motion, move everything except change - // instructions. - if (FLAG_aggressive_loop_invariant_motion && !instr->IsChange()) { - return true; - } - - // Otherwise only move instructions that postdominate the loop header - // (i.e. are always executed inside the loop). This is to avoid - // unnecessary deoptimizations assuming the loop is executed at least - // once. TODO(fschneider): Better type feedback should give us - // information about code that was never executed. - HBasicBlock* block = instr->block(); - bool result = true; - if (block != loop_header) { - for (int i = 1; i < loop_header->predecessors()->length(); ++i) { - bool found = false; - HBasicBlock* pred = loop_header->predecessors()->at(i); - while (pred != loop_header) { - if (pred == block) found = true; - pred = pred->dominator(); - } - if (!found) { - result = false; - break; - } - } - } - return result; + // Don't hoist code from never executed paths. + if (instr->block()->IsDeoptimizing()) return false; + return true; } @@ -4850,6 +4825,7 @@ TypeInfo info = oracle()->UnaryType(expr); if (info.IsUninitialized()) { AddInstruction(new(zone()) HSoftDeoptimize); + current_block()->MarkAsDeoptimizing(); info = TypeInfo::Unknown(); } Representation rep = ToRepresentation(info); @@ -4865,6 +4841,7 @@ TypeInfo info = oracle()->UnaryType(expr); if (info.IsUninitialized()) { AddInstruction(new(zone()) HSoftDeoptimize); + current_block()->MarkAsDeoptimizing(); } HInstruction* instr = new(zone()) HBitNot(value); ast_context()->ReturnInstruction(instr, expr->id()); @@ -5100,6 +5077,7 @@ TypeInfo info = oracle()->BinaryType(expr); if (info.IsUninitialized()) { AddInstruction(new(zone()) HSoftDeoptimize); + current_block()->MarkAsDeoptimizing(); info = TypeInfo::Unknown(); } HInstruction* instr = NULL; @@ -5369,6 +5347,7 @@ // Check if this expression was ever executed according to type feedback. if (type_info.IsUninitialized()) { AddInstruction(new(zone()) HSoftDeoptimize); + current_block()->MarkAsDeoptimizing(); type_info = TypeInfo::Unknown(); } Index: src/hydrogen.h =================================================================== --- src/hydrogen.h (revision 8241) +++ src/hydrogen.h (working copy) @@ -143,6 +143,9 @@ bool IsInlineReturnTarget() const { return is_inline_return_target_; } void MarkAsInlineReturnTarget() { is_inline_return_target_ = true; } + bool IsDeoptimizing() const { return is_deoptimizing_; } + void MarkAsDeoptimizing() { is_deoptimizing_ = true; } + inline Zone* zone(); #ifdef DEBUG @@ -175,6 +178,7 @@ ZoneList<int> deleted_phis_; HBasicBlock* parent_loop_header_; bool is_inline_return_target_; + bool is_deoptimizing_; }; -- v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev
