diff options
| -rw-r--r-- | lib/Target/README.txt | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/lib/Target/README.txt b/lib/Target/README.txt index 23503517c0..fd862fe63a 100644 --- a/lib/Target/README.txt +++ b/lib/Target/README.txt @@ -172,3 +172,21 @@ information in the constant folder, so we don't know the endianness of the target! //===---------------------------------------------------------------------===// + +Consider this: + +unsigned short swap_16(unsigned short v) { return (v>>8) | (v<<8); } + +Compiled with the ppc backend: + +_swap_16: + slwi r2, r3, 8 + srwi r3, r3, 8 + or r2, r3, r2 + rlwinm r3, r2, 0, 16, 31 + blr + +The rlwinm (an and by 65535) is dead. The dag combiner should propagate bits +better than that to see this. + +//===---------------------------------------------------------------------===// |