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[7/8] xen/x86: Fix get_cpu_info() when built with clang

Message ID 1455048108-5045-8-git-send-email-andrew.cooper3@citrix.com (mailing list archive)
State New, archived
Headers show

Commit Message

Andrew Cooper Feb. 9, 2016, 8:01 p.m. UTC 
Clang understands the GCCism in use here, but still complains that sp is
unintialised.  In such cases, resort to the older version of this code, which
directly reads %rsp into the temporary variable.

Note that we still keep the GCCism in the default case, as it causes GCC to
create rather better assembly.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
---
 xen/include/asm-x86/current.h | 6 ++++++
 1 file changed, 6 insertions(+)
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Patch

diff --git a/xen/include/asm-x86/current.h b/xen/include/asm-x86/current.h
index f011d2d..15b99ff 100644
--- a/xen/include/asm-x86/current.h
+++ b/xen/include/asm-x86/current.h
@@ -47,7 +47,13 @@  struct cpu_info {
 
 static inline struct cpu_info *get_cpu_info(void)
 {
+#ifdef __clang__
+    /* Clang complains that sp in the else case is not initialised. */
+    unsigned long sp;
+    asm ( "mov %%rsp, %0" : "=r" (sp) );
+#else
     register unsigned long sp asm("rsp");
+#endif
 
     return (struct cpu_info *)((sp & ~(STACK_SIZE-1)) + STACK_SIZE) - 1;
 }