Compressed native PC for stack maps

Compress native PC based on instruction alignment. This reduces the
size of stack maps, boot.oat is 0.4% smaller for arm64.

Test: test-art-host, test-art-target, N6P booting

Change-Id: I2b70eecabda88b06fa80a85688fd992070d54278

1 files changed, 19 insertions, 0 deletions

diff --git a/runtime/arch/instruction_set.h b/runtime/arch/instruction_set.h
index 4a8bea45e5..99aea62468 100644
--- a/runtime/arch/instruction_set.h
+++ b/runtime/arch/instruction_set.h
@@ -75,6 +75,14 @@ static constexpr size_t kMipsAlignment = 8;
 // X86 instruction alignment. This is the recommended alignment for maximum performance.
 static constexpr size_t kX86Alignment = 16;
 
+// Different than code alignment since code alignment is only first instruction of method.
+static constexpr size_t kThumb2InstructionAlignment = 2;
+static constexpr size_t kArm64InstructionAlignment = 4;
+static constexpr size_t kX86InstructionAlignment = 1;
+static constexpr size_t kX86_64InstructionAlignment = 1;
+static constexpr size_t kMipsInstructionAlignment = 2;
+static constexpr size_t kMips64InstructionAlignment = 2;
+
 const char* GetInstructionSetString(InstructionSet isa);
 
 // Note: Returns kNone when the string cannot be parsed to a known value.
@@ -106,6 +114,17 @@ static inline PointerSize GetInstructionSetPointerSize(InstructionSet isa) {
   }
 }
 
+ALWAYS_INLINE static inline constexpr size_t GetInstructionSetInstructionAlignment(
+    InstructionSet isa) {
+  return (isa == kThumb2 || isa == kArm) ? kThumb2InstructionAlignment :
+         (isa == kArm64) ? kArm64InstructionAlignment :
+         (isa == kX86) ? kX86InstructionAlignment :
+         (isa == kX86_64) ? kX86_64InstructionAlignment :
+         (isa == kMips) ? kMipsInstructionAlignment :
+         (isa == kMips64) ? kMips64InstructionAlignment :
+         0;  // Invalid case, but constexpr doesn't support asserts.
+}
+
 static inline bool IsValidInstructionSet(InstructionSet isa) {
   switch (isa) {
     case kArm: