Thumb2: Reduce memory used for fixup dependencies.

Mark fixups for far backward branches as 32-bit from the
beginning and ignore their dependencies since they cannot
be expanded anymore. This reduces the memory used by the
fixup_dependents_ when compiling methods with a lot of
slow paths.

Bug: 28256882
Change-Id: I0b7155ed8970b69703fa9c4666d9c4961e425721

1 files changed, 14 insertions, 0 deletions

diff --git a/compiler/utils/arm/assembler_thumb2.h b/compiler/utils/arm/assembler_thumb2.h
index 111a6b09d7..bc5b708e88 100644
--- a/compiler/utils/arm/assembler_thumb2.h
+++ b/compiler/utils/arm/assembler_thumb2.h
@@ -538,6 +538,20 @@ class Thumb2Assembler FINAL : public ArmAssembler {
       return GetType() >= kLoadLiteralNarrow;
     }
 
+    // Returns whether the Fixup can expand from the original size.
+    bool CanExpand() const {
+      switch (GetOriginalSize()) {
+        case kBranch32Bit:
+        case kCbxz48Bit:
+        case kLiteralFar:
+        case kLiteralAddrFar:
+        case kLongOrFPLiteralFar:
+          return false;
+        default:
+          return true;
+      }
+    }
+
     Size GetOriginalSize() const {
       return original_size_;
     }