V4: Tweak "enable JIT" ifdefs.

- indentation, to make it readable
- on arm64: only enable for Linux (but only after future testing!)
- add CONFIG+=force-compile-jit handling so the JIT can be compiled/used
  even on platforms that don't officially support it (like iOS, where it
  works if you run from Xcode). This is done for debugging purposes.

Change-Id: I8611ba409e10305f480463a16d88bc854b1c218a
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

3 files changed, 22 insertions, 13 deletions

diff --git a/src/3rdparty/masm/masm-defs.pri b/src/3rdparty/masm/masm-defs.pri
index bfcccfeeaa..c4c7d3ce9a 100644
--- a/src/3rdparty/masm/masm-defs.pri
+++ b/src/3rdparty/masm/masm-defs.pri
@@ -30,6 +30,10 @@ disassembler {
     DEFINES += WTF_USE_UDIS86=0
 }
 
+force-compile-jit {
+    DEFINES += V4_FORCE_COMPILE_JIT
+}
+
 INCLUDEPATH += $$PWD/disassembler
 INCLUDEPATH += $$PWD/disassembler/udis86
 INCLUDEPATH += $$_OUT_PWD
diff --git a/src/qml/jit/qv4targetplatform_p.h b/src/qml/jit/qv4targetplatform_p.h
index 878c1dd9fd..80a18a7f5b 100644
--- a/src/qml/jit/qv4targetplatform_p.h
+++ b/src/qml/jit/qv4targetplatform_p.h
@@ -82,7 +82,7 @@ namespace JIT {
 class TargetPlatform
 {
 public:
-#if CPU(X86) && (OS(LINUX) || OS(WINDOWS) || OS(QNX) || OS(FREEBSD))
+#if CPU(X86) && (OS(LINUX) || OS(WINDOWS) || OS(QNX) || OS(FREEBSD) || defined(Q_OS_IOS))
     enum { RegAllocIsSupported = 1 };
 
     static const JSC::MacroAssembler::RegisterID FramePointerRegister   = JSC::X86Registers::ebp;
@@ -151,7 +151,7 @@ public:
 
 #endif // Windows on x86
 
-#if CPU(X86_64) && (OS(LINUX) || OS(MAC_OS_X) || OS(FREEBSD))
+#if CPU(X86_64) && (OS(LINUX) || OS(MAC_OS_X) || OS(FREEBSD) || defined(Q_OS_IOS))
     enum { RegAllocIsSupported = 1 };
 
     static const JSC::MacroAssembler::RegisterID FramePointerRegister   = JSC::X86Registers::ebp;
diff --git a/src/qml/jsruntime/qv4global_p.h b/src/qml/jsruntime/qv4global_p.h
index 99ba1ec81c..b0850a9db3 100644
--- a/src/qml/jsruntime/qv4global_p.h
+++ b/src/qml/jsruntime/qv4global_p.h
@@ -93,22 +93,22 @@ inline double trunc(double d) { return d > 0 ? floor(d) : ceil(d); }
 
 #if defined(Q_PROCESSOR_X86) && !defined(__ILP32__) \
     && (defined(Q_OS_WIN) || defined(Q_OS_LINUX) || defined(Q_OS_QNX) || defined(Q_OS_FREEBSD))
-#define V4_ENABLE_JIT
+#  define V4_ENABLE_JIT
 #elif defined(Q_PROCESSOR_X86_64) && !defined(__ILP32__) \
     && (defined(Q_OS_WIN) || defined(Q_OS_LINUX) || defined(Q_OS_MAC) || defined(Q_OS_FREEBSD))
-#define V4_ENABLE_JIT
+#  define V4_ENABLE_JIT
 #elif defined(Q_PROCESSOR_ARM_32)
-
-#if defined(thumb2) || defined(__thumb2__) || ((defined(__thumb) || defined(__thumb__)) && __TARGET_ARCH_THUMB-0 == 4)
-#define V4_ENABLE_JIT
-#elif defined(__ARM_ARCH_ISA_THUMB) && __ARM_ARCH_ISA_THUMB == 2 // clang 3.5 and later will set this if the core supports the Thumb-2 ISA.
-#define V4_ENABLE_JIT
-#endif
-
+#  if defined(thumb2) || defined(__thumb2__) || ((defined(__thumb) || defined(__thumb__)) && __TARGET_ARCH_THUMB-0 == 4)
+#    define V4_ENABLE_JIT
+#  elif defined(__ARM_ARCH_ISA_THUMB) && __ARM_ARCH_ISA_THUMB == 2 // clang 3.5 and later will set this if the core supports the Thumb-2 ISA.
+#    define V4_ENABLE_JIT
+#  endif
 #elif defined(Q_PROCESSOR_ARM_64)
-#define V4_ENABLE_JIT // iOS is disabled below.
+#  if defined(Q_OS_LINUX) && 0 // TODO: test on Linux/aarch64 before enabling this
+#    define V4_ENABLE_JIT
+#  endif
 #elif defined(Q_PROCESSOR_MIPS_32) && defined(Q_OS_LINUX)
-#define V4_ENABLE_JIT
+#  define V4_ENABLE_JIT
 #endif
 
 // Black list some platforms
@@ -118,6 +118,11 @@ inline double trunc(double d) { return d > 0 ? floor(d) : ceil(d); }
 #endif
 #endif
 
+// For debug purposes: add CONFIG+=force-compile-jit to qmake's command-line to always compile the JIT.
+#if defined(V4_FORCE_COMPILE_JIT) && !defined(V4_ENABLE_JIT)
+#  define V4_ENABLE_JIT
+#endif
+
 // Do certain things depending on whether the JIT is enabled or disabled
 
 #ifdef V4_ENABLE_JIT