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

1 files changed, 4 insertions, 4 deletions

diff --git a/compiler/optimizing/ssa_builder.cc b/compiler/optimizing/ssa_builder.cc
index f6bab8efcb..207e3f3b44 100644
--- a/compiler/optimizing/ssa_builder.cc
+++ b/compiler/optimizing/ssa_builder.cc
@@ -68,7 +68,7 @@ void SsaBuilder::FixNullConstantType() {
       // should be replaced with a null constant.
       // Both type propagation and redundant phi elimination ensure `int_operand`
       // can only be the 0 constant.
-      DCHECK(int_operand->IsIntConstant());
+      DCHECK(int_operand->IsIntConstant()) << int_operand->DebugName();
       DCHECK_EQ(0, int_operand->AsIntConstant()->GetValue());
       equality_instr->ReplaceInput(GetGraph()->GetNullConstant(), int_operand == right ? 1 : 0);
     }
@@ -422,7 +422,7 @@ bool SsaBuilder::FixAmbiguousArrayOps() {
   return true;
 }
 
-BuildSsaResult SsaBuilder::BuildSsa() {
+GraphAnalysisResult SsaBuilder::BuildSsa() {
   // 1) Visit in reverse post order. We need to have all predecessors of a block
   // visited (with the exception of loops) in order to create the right environment
   // for that block. For loops, we create phis whose inputs will be set in 2).
@@ -462,7 +462,7 @@ BuildSsaResult SsaBuilder::BuildSsa() {
   // computed the type of the array input, the ambiguity can be resolved and the
   // correct equivalents kept.
   if (!FixAmbiguousArrayOps()) {
-    return kBuildSsaFailAmbiguousArrayOp;
+    return kAnalysisFailAmbiguousArrayOp;
   }
 
   // 8) Mark dead phis. This will mark phis which are not used by instructions
@@ -497,7 +497,7 @@ BuildSsaResult SsaBuilder::BuildSsa() {
     }
   }
 
-  return kBuildSsaSuccess;
+  return kAnalysisSuccess;
 }
 
 ArenaVector<HInstruction*>* SsaBuilder::GetLocalsFor(HBasicBlock* block) {