[PowerPC] Remove README.txt entry

This entry has been rendered irrelevant now that we have proper CR bit
tracking.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225211 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/README.txt

@@ -184,40 +184,6 @@ just fastcc.
 
 ===-------------------------------------------------------------------------===
 
-Compile this:
-
-int foo(int a) {
-  int b = (a < 8);
-  if (b) {
-    return b * 3;     // ignore the fact that this is always 3.
-  } else {
-    return 2;
-  }
-}
-
-into something not this:
-
-_foo:
-1)      cmpwi cr7, r3, 8
-        mfcr r2, 1
-        rlwinm r2, r2, 29, 31, 31
-1)      cmpwi cr0, r3, 7
-        bgt cr0, LBB1_2 ; UnifiedReturnBlock
-LBB1_1: ; then
-        rlwinm r2, r2, 0, 31, 31
-        mulli r3, r2, 3
-        blr
-LBB1_2: ; UnifiedReturnBlock
-        li r3, 2
-        blr
-
-In particular, the two compares (marked 1) could be shared by reversing one.
-This could be done in the dag combiner, by swapping a BR_CC when a SETCC of the
-same operands (but backwards) exists.  In this case, this wouldn't save us 
-anything though, because the compares still wouldn't be shared.
-
-===-------------------------------------------------------------------------===
-
 Fold add and sub with constant into non-extern, non-weak addresses so this:
 
 static int a;