Clean up the ifdefs on ARM.

Ensure that we use ARMv5 instructions on ARMv6 and ARMv7 CPUs.
Review URL: http://codereview.chromium.org/206012

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@2898 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/arm/codegen-arm.cc

@@ -4335,7 +4335,7 @@ static void CountLeadingZeros(
     Register source,
     Register scratch,
     Register zeros) {
-#ifdef __ARM_ARCH_5__
+#ifdef CAN_USE_ARMV5_INSTRUCTIONS
   __ clz(zeros, source);  // This instruction is only supported after ARM5.
 #else
   __ mov(zeros, Operand(0));

src/arm/constants-arm.h

@@ -43,10 +43,30 @@
 # define USE_THUMB_INTERWORK 1
 #endif
 
+#if defined(__ARM_ARCH_5T__) || \
+    defined(__ARM_ARCH_5TE__) || \
+    defined(__ARM_ARCH_6__) || \
+    defined(__ARM_ARCH_7A__) || \
+    defined(__ARM_ARCH_7__)
+# define CAN_USE_ARMV5_INSTRUCTIONS 1
+# define CAN_USE_THUMB_INSTRUCTIONS 1
+#endif
+
+#if defined(__ARM_ARCH_6__) || \
+    defined(__ARM_ARCH_7A__) || \
+    defined(__ARM_ARCH_7__)
+# define CAN_USE_ARMV6_INSTRUCTIONS 1
+#endif
+
+#if defined(__ARM_ARCH_7A__) || \
+    defined(__ARM_ARCH_7__)
+# define CAN_USE_ARMV7_INSTRUCTIONS 1
+#endif
+
 // Simulator should support ARM5 instructions.
 #if !defined(__arm__)
-# define __ARM_ARCH_5__ 1
-# define __ARM_ARCH_5T__ 1
+# define CAN_USE_ARMV5_INSTRUCTIONS 1
+# define CAN_USE_THUMB_INSTRUCTIONS 1
 #endif
 
 namespace assembler {

src/arm/macro-assembler-arm.cc

@@ -52,21 +52,15 @@ MacroAssembler::MacroAssembler(void* buffer, int size)
 
 
 // We do not support thumb inter-working with an arm architecture not supporting
-// the blx instruction (below v5t)
-#if defined(USE_THUMB_INTERWORK)
-#if !defined(__ARM_ARCH_5T__) && \
-  !defined(__ARM_ARCH_5TE__) &&  \
-  !defined(__ARM_ARCH_6__) &&  \
-  !defined(__ARM_ARCH_7A__) &&   \
-  !defined(__ARM_ARCH_7__)
-// add tests for other versions above v5t as required
-#error "for thumb inter-working we require architecture v5t or above"
-#endif
+// the blx instruction (below v5t).  If you know what CPU you are compiling for
+// you can use -march=armv7 or similar.
+#if defined(USE_THUMB_INTERWORK) && !defined(CAN_USE_THUMB_INSTRUCTIONS)
+# error "For thumb inter-working we require an architecture which supports blx"
 #endif
 
 
 // Using blx may yield better code, so use it when required or when available
-#if defined(USE_THUMB_INTERWORK) || defined(__ARM_ARCH_5__)
+#if defined(USE_THUMB_INTERWORK) || defined(CAN_USE_ARMV5_INSTRUCTIONS)
 #define USE_BLX 1
 #endif