[Qemu-devel] [PATCH] tcg/arm: Use r6 as TCG_AREG0 to avoid clash with Thumb framepointer

[Peter Maydell <peter.maydell@linaro.org>]

On ARM, in Thumb mode r7 is used for the framepointer; this meant
that we would fail to compile in debug mode because we were using r7
for TCG_AREG0. Shift to r6 instead to avoid this clash.
(Bug reported as LP:870990.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
I did an extremely rough-and-ready benchmark with using a highreg
instead and it didn't seem to make any difference, so I've stuck
with using a lowreg as we do at the moment.

 dyngen-exec.h        |    2 +-
 tcg/arm/tcg-target.h |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/dyngen-exec.h b/dyngen-exec.h
index 3544372..09be9ea 100644
--- a/dyngen-exec.h
+++ b/dyngen-exec.h
@@ -31,7 +31,7 @@
 #elif defined(_ARCH_PPC)
 #define AREG0 "r27"
 #elif defined(__arm__)
-#define AREG0 "r7"
+#define AREG0 "r6"
 #elif defined(__hppa__)
 #define AREG0 "r17"
 #elif defined(__mips__)
diff --git a/tcg/arm/tcg-target.h b/tcg/arm/tcg-target.h
index 48586c3..0035b47 100644
--- a/tcg/arm/tcg-target.h
+++ b/tcg/arm/tcg-target.h
@@ -78,7 +78,7 @@ typedef enum {
 
 enum {
     /* Note: must be synced with dyngen-exec.h */
-    TCG_AREG0 = TCG_REG_R7,
+    TCG_AREG0 = TCG_REG_R6,
 };
 
 static inline void flush_icache_range(unsigned long start, unsigned long stop)
-- 
1.7.5.4