[Qemu-devel] [PATCH 09/15] tcg-sparc: Do not use a global register for AREG0.

[Richard Henderson <rth@twiddle.net>]

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 dyngen-exec.h |   20 +++++++++++---------
 exec.c        |   16 ++++++++++++++--
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/dyngen-exec.h b/dyngen-exec.h
index 65fcb43..d673f9f 100644
--- a/dyngen-exec.h
+++ b/dyngen-exec.h
@@ -41,13 +41,8 @@
 #elif defined(__mips__)
 #define AREG0 "s0"
 #elif defined(__sparc__)
-#ifdef CONFIG_SOLARIS
-#define AREG0 "g2"
-#elif HOST_LONG_BITS == 64
-#define AREG0 "g5"
-#else
-#define AREG0 "g6"
-#endif
+/* Don't use a global register.  Working around glibc clobbering these
+   global registers is more trouble than just using TLS.  */
 #elif defined(__s390__)
 #define AREG0 "r10"
 #elif defined(__alpha__)
@@ -62,12 +57,19 @@
 #error unsupported CPU
 #endif
 
-#if defined(AREG0)
+#ifdef AREG0
 register CPUArchState *env asm(AREG0);
 #else
-/* TODO: Try env = cpu_single_env. */
+/* It's tempting to #define env cpu_single_cpu, but that runs afoul of
+   the other macro usage in target-foo/helper.h.  Instead use an alias.
+   That has to happen where cpu_single_cpu is defined, so just a
+   declaration here.  */
+#ifdef __linux__
+extern __thread CPUArchState *env;
+#else
 extern CPUArchState *env;
 #endif
+#endif /* AREG0 */
 
 #endif /* !CONFIG_TCG_PASS_AREG0 */
 #endif /* !defined(__DYNGEN_EXEC_H__) */
diff --git a/exec.c b/exec.c
index 6731ab8..d84caa5 100644
--- a/exec.c
+++ b/exec.c
@@ -124,9 +124,21 @@ static MemoryRegion io_mem_subpage_ram;
 #endif
 
 CPUArchState *first_cpu;
-/* current CPU in the current thread. It is only valid inside
-   cpu_exec() */
+
+/* Current CPU in the current thread. It is only valid inside cpu_exec().  */
 DEFINE_TLS(CPUArchState *,cpu_single_env);
+
+/* In dyngen-exec.h, without AREG0, we fall back to an alias to cpu_single_env.
+   We can't actually tell from here whether that's needed or not, but it does
+   not hurt to go ahead and make the declaration.  */
+#ifndef CONFIG_TCG_PASS_AREG0
+extern
+#ifdef __linux__
+  __thread
+#endif
+  CPUArchState *env __attribute__((alias("tls__cpu_single_env")));
+#endif /* CONFIG_TCG_PASS_AREG0 */
+
 /* 0 = Do not count executed instructions.
    1 = Precise instruction counting.
    2 = Adaptive rate instruction counting.  */
-- 
1.7.7.6