Implement irreducible loop support in optimizing.
So we don't fallback to the interpreter in the presence of
irreducible loops.
Implications:
- A loop pre-header does not necessarily dominate a loop header.
- Non-constant redundant phis will be kept in loop headers, to
satisfy our linear scan register allocation algorithm.
- while-graph optimizations, such as gvn, licm, lse, and dce
need to know when they are dealing with irreducible loops.
Change-Id: I2cea8934ce0b40162d215353497c7f77d6c9137e
diff --git a/compiler/optimizing/ssa_liveness_analysis.cc b/compiler/optimizing/ssa_liveness_analysis.cc
index b9d8731..a5609fc 100644
--- a/compiler/optimizing/ssa_liveness_analysis.cc
+++ b/compiler/optimizing/ssa_liveness_analysis.cc
@@ -273,6 +273,18 @@
}
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()) << instruction->DebugName();
+ DCHECK(instruction->IsCurrentMethod() || instruction->IsConstant())
+ << instruction->DebugName();
+ }
+ }
size_t last_position = block->GetLoopInformation()->GetLifetimeEnd();
// For all live_in instructions at the loop header, we need to create a range
// that covers the full loop.