Add hints when resolving phies and register constraints.

runtime/vm/flow_graph_allocator.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_allocator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/intermediate_language.h"
 #include "vm/il_printer.h"
 #include "vm/flow_graph_builder.h"
@@ skipping 262 matching lines @@
       return;
     } else if (uses_->location_slot() == NULL) {
       uses_->set_location_slot(location_slot);
       return;
     }
   }
   uses_ = new UsePosition(pos, uses_, location_slot);
 }
 
 
+void LiveRange::AddHintedUse(intptr_t pos,
+                             Location* location_slot,
+                             Location* hint) {

[srdjan, 2012/08/07 19:38:20]

AddUseWithHint instead of AddHintedUse?

+  ASSERT(hint != NULL);
+  AddUse(pos, location_slot);
+  uses_->set_hint(hint);
+}
+
+
 void LiveRange::AddUseInterval(intptr_t start, intptr_t end) {
   ASSERT(start < end);
 
   // Live ranges are being build by visiting instructions in post-order.
   // This implies that use intervals will be perpended in a monotonically
   // decreasing order.
   if (first_use_interval() != NULL) {
     // If the first use interval and the use interval we are adding
     // touch then we can just extend the first interval to cover their
     // union.
@@ skipping 260 matching lines @@
       // Expected shape of live ranges:
       //
       //                 g  g'
       //      value    --*
       //
 
       LiveRange* range = GetLiveRange(
           val->AsUse()->definition()->ssa_temp_index());
 
       range->AddUseInterval(block->start_pos(), pos);
-      range->AddUse(pos, move->src_slot());
+      range->AddHintedUse(pos, move->src_slot(), move->dest_slot());
 
       move->set_src(Location::PrefersRegister());
     } else {
       ASSERT(val->IsConstant());
       move->set_src(Location::Constant(val->AsConstant()->value()));
     }
     move_idx++;
   }
 
   // Begin backward iteration with the instruction before the parallel
@@ skipping 124 matching lines @@
       // live ranges:
       //
       //                 j' i  i'
       //      value    --*
       //      register   [-----)
       //
       MoveOperands* move =
           AddMoveAt(pos - 1, *in_ref, Location::Any());
       BlockLocation(*in_ref, pos - 1, pos + 1);
       range->AddUseInterval(block->start_pos(), pos - 1);
-      range->AddUse(pos - 1, move->src_slot());
+      range->AddHintedUse(pos - 1, move->src_slot(), in_ref);
     } else {
       // Normal unallocated input. Expected shape of
       // live ranges:
       //
       //                 i  i'
       //      value    -----*
       //
       ASSERT(in_ref->IsUnallocated());
       range->AddUseInterval(block->start_pos(), pos + 1);
       range->AddUse(pos + 1, in_ref);
@@ skipping 97 matching lines @@
       range->set_first_use(range->first_use()->next());
     }
 
     // Shorten live range to the point of definition, this might make the range
     // empty (if the only use immediately follows). If range is not empty add
     // move from a fixed register to an unallocated location.
     range->DefineAt(pos + 1);
     if (range->Start() == range->End()) return;
 
     MoveOperands* move = AddMoveAt(pos + 1, Location::Any(), *out);
-    range->AddUse(pos + 1, move->dest_slot());
+    range->AddHintedUse(pos + 1, move->dest_slot(), out);
   } else if (output_same_as_first_input) {
     // Output register will contain a value of the first input at instruction's
     // start. Expected shape of live ranges:
     //
     //                 i  i'
     //    input #0   --*
     //    output       [----
     //
     ASSERT(locs->in_slot(0)->Equals(Location::RequiresRegister()));
 
@@ skipping 498 matching lines @@
 
 
 
 bool FlowGraphAllocator::AllocateFreeRegister(LiveRange* unallocated) {
   Register candidate = kNoRegister;
   intptr_t free_until = 0;
 
   // If hint is available try hint first.
   // TODO(vegorov): ensure that phis are hinted on the back edge.
   Location hint = unallocated->finger()->FirstHint();
-  if (!hint.IsInvalid()) {
-    ASSERT(hint.IsRegister());
-
+  if (hint.IsRegister()) {
     if (!blocked_cpu_regs_[hint.reg()]) {
       free_until = FirstIntersectionWithAllocated(hint.reg(), unallocated);
       candidate = hint.reg();
     }
 
     TRACE_ALLOC(OS::Print("found hint "));
     TRACE_ALLOC(hint.Print());
     TRACE_ALLOC(OS::Print(" for %d: free until %d\n",
                           unallocated->vreg(), free_until));
-  }
-
-  if (free_until != kMaxPosition) {
+  } else if (free_until != kMaxPosition) {
     for (intptr_t reg = 0; reg < kNumberOfCpuRegisters; ++reg) {
       if (!blocked_cpu_regs_[reg] && cpu_regs_[reg].length() == 0) {
         candidate = static_cast<Register>(reg);
         free_until = kMaxPosition;
         break;
       }
     }
   }
 
   ASSERT(0 <= kMaxPosition);
@@ skipping 513 matching lines @@
     OS::Print("-- [after ssa allocator] ir [%s] -------------\n",
               function.ToFullyQualifiedCString());
     FlowGraphPrinter printer(Function::Handle(), block_order_, true);
     printer.PrintBlocks();
     OS::Print("----------------------------------------------\n");
   }
 }
 
 
 }  // namespace dart