For 32-bit ARM devices align method headers and code to 64-byte

boundaries.

For other architectures, move back to instruction set alignment.

Rename kJitCodeCacheAlignment to kJitCodeAccountingBytes since it's
now only used for accounting rather than alignment.

Bug: 132205399
Test: manual (described in bug)
Merged-In: I88f5f39381bf0331ce8540a929c6a68b3b5e0c75
Change-Id: I88f5f39381bf0331ce8540a929c6a68b3b5e0c75

1 files changed, 7 insertions, 8 deletions

diff --git a/runtime/jit/jit_code_cache.h b/runtime/jit/jit_code_cache.h
index a3e10c75af..df58f19722 100644
--- a/runtime/jit/jit_code_cache.h
+++ b/runtime/jit/jit_code_cache.h
@@ -74,14 +74,13 @@ namespace jit {
 class MarkCodeClosure;
 class ScopedCodeCacheWrite;
 
-// Alignment in bytes that will suit all architectures for JIT code cache allocations.  The
-// allocated block is used for method header followed by generated code. Allocations should be
-// aligned to avoid sharing cache lines between different allocations. The alignment should be
-// determined from the hardware, but this isn't readily exposed in userland plus some hardware
-// misreports.
-static constexpr int kJitCodeAlignment = 64;
-
-using CodeCacheBitmap = gc::accounting::MemoryRangeBitmap<kJitCodeAlignment>;
+// Number of bytes represented by a bit in the CodeCacheBitmap. Value is reasonable for all
+// architectures.
+static constexpr int kJitCodeAccountingBytes = 16;
+
+// Type of bitmap used for tracking live functions in the JIT code cache for the purposes
+// of garbage collecting code.
+using CodeCacheBitmap = gc::accounting::MemoryRangeBitmap<kJitCodeAccountingBytes>;
 
 class JitCodeCache {
  public: