Iterative move coalescing for gc regalloc

Implement iterative move coalescing for graph coloring
register allocation. Based on Andrew Appel's implementation
in "Modern Compiler Implementation in Java", modified to
support constraints such as pair intervals.

Test: ART_TEST_OPTIMIZING_GRAPH_COLOR=true m test-art-host

Change-Id: I8642297d3bd798a4fc4de4b356ac3304098471a5

1 files changed, 3 insertions, 1 deletions

diff --git a/compiler/optimizing/ssa_liveness_analysis.h b/compiler/optimizing/ssa_liveness_analysis.h
index 346753b775..92788fe6b8 100644
--- a/compiler/optimizing/ssa_liveness_analysis.h
+++ b/compiler/optimizing/ssa_liveness_analysis.h
@@ -514,7 +514,9 @@ class LiveInterval : public ArenaObject<kArenaAllocSsaLiveness> {
 
   // Whether the interval requires a register rather than a stack location.
   // If needed for performance, this could be cached.
-  bool RequiresRegister() const { return FirstRegisterUse() != kNoLifetime; }
+  bool RequiresRegister() const {
+    return !HasRegister() && FirstRegisterUse() != kNoLifetime;
+  }
 
   size_t FirstUseAfter(size_t position) const {
     if (is_temp_) {