Commit Graph

4 Commits

Author SHA1 Message Date
Evan Cheng 21b0348199 Disable the Thumb no-return call optimization:
mov lr, pc
b.w _foo

The "mov" instruction doesn't set bit zero to one, it's putting incorrect
value in lr. It messes up backtraces.

rdar://12663632

llvm-svn: 167657
2012-11-10 02:09:05 +00:00
Bob Wilson e8a549cd92 Add LLVM support for Swift.
llvm-svn: 164899
2012-09-29 21:43:49 +00:00
Daniel Dunbar ee7b899343 Revert r151623 "Some ARM implementaions, e.g. A-series, does return stack prediction. ...", it is breaking the Clang build during the Compiler-RT part.
llvm-svn: 151630
2012-02-28 15:36:07 +00:00
Evan Cheng 87c7b09d8d Some ARM implementaions, e.g. A-series, does return stack prediction. That is,
the processor keeps a return addresses stack (RAS) which stores the address
and the instruction execution state of the instruction after a function-call
type branch instruction.

Calling a "noreturn" function with normal call instructions (e.g. bl) can
corrupt RAS and causes 100% return misprediction so LLVM should use a
unconditional branch instead. i.e.
mov lr, pc
b _foo
The "mov lr, pc" is issued in order to get proper backtrace.

rdar://8979299

llvm-svn: 151623
2012-02-28 06:42:03 +00:00