[compiler-rt] r331626 - [sanitizer] Be more accurate when calculating the previous instruction address on ARM.

[Igor Kudrin via llvm-commits]

Author: ikudrin
Date: Mon May  7 03:07:22 2018
New Revision: 331626

URL: http://llvm.org/viewvc/llvm-project?rev=331626&view=rev
Log:
[sanitizer] Be more accurate when calculating the previous instruction address on ARM.

Differential Revision: https://reviews.llvm.org/D46004

Modified:
    compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.h

Modified: compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.h?rev=331626&r1=331625&r2=331626&view=diff
==============================================================================
--- compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.h (original)
+++ compiler-rt/trunk/lib/sanitizer_common/sanitizer_stacktrace.h Mon May  7 03:07:22 2018
@@ -75,10 +75,11 @@ struct StackTrace {
 ALWAYS_INLINE
 uptr StackTrace::GetPreviousInstructionPc(uptr pc) {
 #if defined(__arm__)
-  // Cancel Thumb bit.
-  pc = pc & (~1);
-#endif
-#if defined(__powerpc__) || defined(__powerpc64__)
+  // T32 (Thumb) branch instructions can be 16 or 32 bit long,
+  // so we return (pc-2) in that case in order to be safe.
+  // For A32 mode we return (pc-4) because all instructions are 32 bit long.
+  return (pc - 3) & (~1);
+#elif defined(__powerpc__) || defined(__powerpc64__) || defined(__aarch64__)
   // PCs are always 4 byte aligned.
   return pc - 4;
 #elif defined(__sparc__) || defined(__mips__)