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, 13 insertions, 5 deletions

diff --git a/compiler/optimizing/code_generator_arm.cc b/compiler/optimizing/code_generator_arm.cc
index 58feb67a58..9a1f2b8717 100644
--- a/compiler/optimizing/code_generator_arm.cc
+++ b/compiler/optimizing/code_generator_arm.cc
@@ -5980,8 +5980,16 @@ void CodeGeneratorARM::GenerateReadBarrierForRoot(HInstruction* instruction,
 HInvokeStaticOrDirect::DispatchInfo CodeGeneratorARM::GetSupportedInvokeStaticOrDirectDispatch(
       const HInvokeStaticOrDirect::DispatchInfo& desired_dispatch_info,
       MethodReference target_method) {
-  if (desired_dispatch_info.code_ptr_location ==
-      HInvokeStaticOrDirect::CodePtrLocation::kCallPCRelative) {
+  HInvokeStaticOrDirect::DispatchInfo dispatch_info = desired_dispatch_info;
+  // We disable pc-relative load when there is an irreducible loop, as the optimization
+  // is incompatible with it.
+  if (GetGraph()->HasIrreducibleLoops() &&
+      (dispatch_info.method_load_kind ==
+          HInvokeStaticOrDirect::MethodLoadKind::kDexCachePcRelative)) {
+    dispatch_info.method_load_kind = HInvokeStaticOrDirect::MethodLoadKind::kDexCacheViaMethod;
+  }
+
+  if (dispatch_info.code_ptr_location == HInvokeStaticOrDirect::CodePtrLocation::kCallPCRelative) {
     const DexFile& outer_dex_file = GetGraph()->GetDexFile();
     if (&outer_dex_file != target_method.dex_file) {
       // Calls across dex files are more likely to exceed the available BL range,
@@ -5992,14 +6000,14 @@ HInvokeStaticOrDirect::DispatchInfo CodeGeneratorARM::GetSupportedInvokeStaticOr
           ? HInvokeStaticOrDirect::CodePtrLocation::kCallDirectWithFixup
           : HInvokeStaticOrDirect::CodePtrLocation::kCallArtMethod;
       return HInvokeStaticOrDirect::DispatchInfo {
-        desired_dispatch_info.method_load_kind,
+        dispatch_info.method_load_kind,
         code_ptr_location,
-        desired_dispatch_info.method_load_data,
+        dispatch_info.method_load_data,
         0u
       };
     }
   }
-  return desired_dispatch_info;
+  return dispatch_info;
 }
 
 Register CodeGeneratorARM::GetInvokeStaticOrDirectExtraParameter(HInvokeStaticOrDirect* invoke,