From 8218b6ec1976c10baefabc5927c29cac1f3ca8e6 Mon Sep 17 00:00:00 2001
From: mikaelpeltier <mikaelpeltier@google.com>
Date: Tue, 4 Jul 2017 13:26:57 +0200
Subject: Update test comparing used registers with highest register number

- It allow to save about 6k when dexing deploy.jar of GMS core v10.

Change-Id: I5bf56a3e24d0634fc797706d352c175bd9f19c6d
---
 .../tools/r8/ir/regalloc/LinearScanRegisterAllocator.java  | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

(limited to 'src/main/java/com/android/tools/r8/ir/regalloc')

diff --git a/src/main/java/com/android/tools/r8/ir/regalloc/LinearScanRegisterAllocator.java b/src/main/java/com/android/tools/r8/ir/regalloc/LinearScanRegisterAllocator.java
index ee25b83cd..19392017c 100644
--- a/src/main/java/com/android/tools/r8/ir/regalloc/LinearScanRegisterAllocator.java
+++ b/src/main/java/com/android/tools/r8/ir/regalloc/LinearScanRegisterAllocator.java
@@ -169,19 +169,19 @@ public class LinearScanRegisterAllocator implements RegisterAllocator {
     insertArgumentMoves();
     BasicBlock[] blocks = computeLivenessInformation();
     // First attempt to allocate register allowing argument reuse. This will fail if spilling
-    // is required or if we end up using more than 15 registers.
+    // is required or if we end up using more than 16 registers.
     boolean noSpilling =
         performAllocationWithoutMoveInsertion(ArgumentReuseMode.ALLOW_ARGUMENT_REUSE);
-    if (!noSpilling || registersUsed() > MAX_SMALL_REGISTER) {
+    if (!noSpilling || (highestUsedRegister() > MAX_SMALL_REGISTER)) {
       // Redo allocation disallowing argument reuse. This always succeeds.
       clearRegisterAssignments();
       performAllocation(ArgumentReuseMode.DISALLOW_ARGUMENT_REUSE);
     } else {
       // Insert spill and phi moves after allocating with argument reuse. If the moves causes
-      // the method to use more than 15 registers we redo allocation disallowing argument
+      // the method to use more than 16 registers we redo allocation disallowing argument
       // reuse. This very rarely happens in practice (12 methods on GMSCore v4 hits that case).
       insertMoves();
-      if (registersUsed() > MAX_SMALL_REGISTER) {
+      if (highestUsedRegister() > MAX_SMALL_REGISTER) {
         // Redo allocation disallowing argument reuse. This always succeeds.
         clearRegisterAssignments();
         removeSpillAndPhiMoves();
@@ -404,6 +404,10 @@ public class LinearScanRegisterAllocator implements RegisterAllocator {
         getRegisterForValue(value, instructionNumber) + value.requiredRegisters() - 1);
   }
 
+  public int highestUsedRegister() {
+    return registersUsed() - 1;
+  }
+
   @Override
   public int registersUsed() {
     int numberOfRegister = maxRegisterNumber + 1 - NUMBER_OF_SENTINEL_REGISTERS;
@@ -472,7 +476,7 @@ public class LinearScanRegisterAllocator implements RegisterAllocator {
       assert intervals.getRegisterLimit() == Constants.U16BIT_MAX;
       boolean canUseArgumentRegister = true;
       for (LiveIntervals child : intervals.getSplitChildren()) {
-        if (child.getRegisterLimit() < registersUsed()) {
+        if (child.getRegisterLimit() < highestUsedRegister()) {
           canUseArgumentRegister = false;
           break;
         }
-- 
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