Refactor handling of input records.

Introduce HInstruction::GetInputRecords(), a new virtual
function that returns an ArrayRef<> to all input records.
Implement all other functions dealing with input records as
wrappers around GetInputRecords(). Rewrite functions that
previously used multiple virtual calls to deal with input
records, especially in loops, to prefetch the ArrayRef<>
only once for each instruction.  Besides avoiding all the
extra calls, this also allows the compiler (clang++) to
perform additional optimizations.

This speeds up the Nexus 5 boot image compilation by ~0.5s
(4% of "Compile Dex File", 2% of dex2oat time) on AOSP ToT.

Change-Id: Id8ebe0fb9405e38d918972a11bd724146e4ca578

1 files changed, 4 insertions, 3 deletions

diff --git a/compiler/optimizing/register_allocator.cc b/compiler/optimizing/register_allocator.cc
index 4405b803e0..4a6b835e80 100644
--- a/compiler/optimizing/register_allocator.cc
+++ b/compiler/optimizing/register_allocator.cc
@@ -305,7 +305,7 @@ void RegisterAllocator::ProcessInstruction(HInstruction* instruction) {
     BlockRegisters(position, position + 1, /* caller_save_only */ true);
   }
 
-  for (size_t i = 0; i < instruction->InputCount(); ++i) {
+  for (size_t i = 0; i < locations->GetInputCount(); ++i) {
     Location input = locations->InAt(i);
     if (input.IsRegister() || input.IsFpuRegister()) {
       BlockRegister(input, position, position + 1);
@@ -753,10 +753,11 @@ bool RegisterAllocator::TryAllocateFreeReg(LiveInterval* current) {
   if (defined_by != nullptr && !current->IsSplit()) {
     LocationSummary* locations = defined_by->GetLocations();
     if (!locations->OutputCanOverlapWithInputs() && locations->Out().IsUnallocated()) {
-      for (size_t i = 0, e = defined_by->InputCount(); i < e; ++i) {
+      auto&& inputs = defined_by->GetInputs();
+      for (size_t i = 0; i < inputs.size(); ++i) {
         // Take the last interval of the input. It is the location of that interval
         // that will be used at `defined_by`.
-        LiveInterval* interval = defined_by->InputAt(i)->GetLiveInterval()->GetLastSibling();
+        LiveInterval* interval = inputs[i]->GetLiveInterval()->GetLastSibling();
         // Note that interval may have not been processed yet.
         // TODO: Handle non-split intervals last in the work list.
         if (locations->InAt(i).IsValid()