The floating-point record forms on PPC don't set the condition register bits
based on a comparison with zero (like the integer record forms do), but rather
based on the exception status bits.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181423 91177308-0d34-0410-b5e6-96231b3b80d8
When matching a compare with a subtract where the arguments of the compare are
swapped w.r.t. the arguments of the subtract, we need to negate the predicates
(or CR bit indices) of the users. This, however, is not the same as inverting
the predicate (negating LT -> GT, but inverting LT -> GE, for example). The ARM
backend seems to do this correctly, but when I adapted the code for the PPC
backend, I introduced an error in this logic.
Comparison optimization is now enabled again by default.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179899 91177308-0d34-0410-b5e6-96231b3b80d8
This seems to cause a stage-2 LLVM compile failure (by crashing TableGen); do
I'm disabling this for now.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179807 91177308-0d34-0410-b5e6-96231b3b80d8
Many PPC instructions have a so-called 'record form' which stores to a specific
condition register the result of comparing the result of the instruction with
zero (always as a signed comparison). For integer operations on PPC64, this is
always a 64-bit comparison.
This implementation is derived from the implementation in the ARM backend;
there are some differences because PPC condition registers are allocatable
virtual registers (although the record forms always use a specific one), and we
look for a matching subtraction instruction after the compare (but before the
first use) in addition to before it.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@179802 91177308-0d34-0410-b5e6-96231b3b80d8
