Fix another case of live_in at irreducible loop entry.

GVN was implicitly extending the liveness of an instruction across
an irreducible loop.

Fix this problem by clearing the value set at loop entries that contain
an irreducible loop.

bug:28252896

(cherry picked from commit 77ce6430af2709432b22344ed656edd8ec80581b)

Change-Id: Ie0121e83b2dfe47bcd184b90a69c0194d13fce54

1 files changed, 5 insertions, 11 deletions

diff --git a/compiler/optimizing/ssa_liveness_analysis.cc b/compiler/optimizing/ssa_liveness_analysis.cc
index 5534aeac29..36e0d993d1 100644
--- a/compiler/optimizing/ssa_liveness_analysis.cc
+++ b/compiler/optimizing/ssa_liveness_analysis.cc
@@ -309,17 +309,8 @@ void SsaLivenessAnalysis::ComputeLiveRanges() {
     }
 
     if (block->IsLoopHeader()) {
-      if (kIsDebugBuild && block->GetLoopInformation()->IsIrreducible()) {
-        // To satisfy our liveness algorithm, we need to ensure loop headers of
-        // irreducible loops do not have any live-in instructions, except constants
-        // and the current method, which can be trivially re-materialized.
-        for (uint32_t idx : live_in->Indexes()) {
-          HInstruction* instruction = GetInstructionFromSsaIndex(idx);
-          DCHECK(instruction->GetBlock()->IsEntryBlock()) << instruction->DebugName();
-          DCHECK(!instruction->IsParameterValue());
-          DCHECK(instruction->IsCurrentMethod() || instruction->IsConstant())
-              << instruction->DebugName();
-        }
+      if (kIsDebugBuild) {
+        CheckNoLiveInIrreducibleLoop(*block);
       }
       size_t last_position = block->GetLoopInformation()->GetLifetimeEnd();
       // For all live_in instructions at the loop header, we need to create a range
@@ -344,6 +335,9 @@ void SsaLivenessAnalysis::ComputeLiveInAndLiveOutSets() {
       // change in this loop), and the live_out set.  If the live_out
       // set does not change, there is no need to update the live_in set.
       if (UpdateLiveOut(block) && UpdateLiveIn(block)) {
+        if (kIsDebugBuild) {
+          CheckNoLiveInIrreducibleLoop(block);
+        }
         changed = true;
       }
     }