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Re: [Xen-devel] [PATCH 07/12] xen/arm: cpuerrata: Match register size with value size in check_workaround_*
Hi,
On 4/17/19 9:28 PM, Stefano Stabellini wrote:
On Wed, 27 Mar 2019, Julien Grall wrote:
Clang is pickier than GCC for the register size in asm statement. It
expects the register size to match the value size.
The asm statement expects a 32-bit (resp. 64-bit) value on Arm32
(resp. Arm64) whereas the value is a boolean (Clang consider to be
32-bit).
It would be possible to impose 32-bit register for both architecture
but this require the code to use __OP32. However, it does not really
improve the assembly generated. Instead, replace switch the variable
to use register_t.
Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
---
xen/include/asm-arm/cpuerrata.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/xen/include/asm-arm/cpuerrata.h b/xen/include/asm-arm/cpuerrata.h
index 55ddfda272..88ef3ca934 100644
--- a/xen/include/asm-arm/cpuerrata.h
+++ b/xen/include/asm-arm/cpuerrata.h
@@ -14,7 +14,7 @@ static inline bool check_workaround_##erratum(void)
\
return false; \
else \
{ \
- bool ret; \
+ register_t ret; \
\
asm volatile (ALTERNATIVE("mov %0, #0", \
"mov %0, #1", \
This is OK. Could you please also change the return statement below?
Maybe something like:
return unlikely(!!ret);
Why? The compiler will implicitly convert the int to bool. 0 will turn
to false, all the other will be true.
We actually been actively removing !! when the type is bool (see the
example in get_paged_frame in common/grant_table.c).
Cheers,
--
Julien Grall
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