[compiler-rt] [msan] Variadic support for AArch64

[zatrazz]

Summary

Now with variadic support for msan on aarch6 there is no need for
XFAIL signal_stress_test anymore. Also to garantee aligned stores
for the FP/SIMD arguments enforce the '__msan_va_arg_tls' alignment
to sizeof the SIMD register (16).

This patch relies on llvm patch http://reviews.llvm.org/D15386

[eugenis]

lib/msan/msan.cc

58

This only aligns the first element of the array. Why is that sufficient?
Do you need to change instrumentation as well to align each next store location to 16 bytes?

[eugenis]

lib/msan/msan.cc

58

OK, just saw the instrumentation change.

[zatrazz]

lib/msan/msan.cc

58

Aligning the first element is just what it requires, since the instrumentation phase will store in a 16 aligned offset (64 currently).

[eugenis]

LGTM, once the llvm change is in.

lib/msan/msan.cc

 
 SANITIZER_INTERFACE_ATTRIBUTE
 THREADLOCAL u64 __msan_retval_tls[kMsanRetvalTlsSize / sizeof(u64)];
 
 SANITIZER_INTERFACE_ATTRIBUTE
 THREADLOCAL u32 __msan_retval_origin_tls;
 
 SANITIZER_INTERFACE_ATTRIBUTE
-THREADLOCAL u64 __msan_va_arg_tls[kMsanParamTlsSize / sizeof(u64)];
+ALIGNED(16) THREADLOCAL u64 __msan_va_arg_tls[kMsanParamTlsSize / sizeof(u64)];
 
 SANITIZER_INTERFACE_ATTRIBUTE
 THREADLOCAL u64 __msan_va_arg_overflow_size_tls;
 
 SANITIZER_INTERFACE_ATTRIBUTE
 THREADLOCAL u32 __msan_origin_tls;
 
 static THREADLOCAL int is_in_symbolizer;

test/msan/signal_stress_test.cc

 // RUN: %clangxx_msan -std=c++11 -O0 %s -o %t && %run %t
 //
-// AArch64 lacks var args instrumentation.
-// XFAIL: aarch64
-
 // Test that va_arg shadow from a signal handler does not leak outside.
 
 #include <signal.h>
 #include <stdarg.h>
 #include <sanitizer/msan_interface.h>
 #include <assert.h>
 #include <sys/time.h>
 #include <stdio.h>