Add intelligence about where to break large blocks.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@34755 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 13 deletions

diff --git a/lib/Target/ARM/README.txt b/lib/Target/ARM/README.txt
index 9f285812a8..5892ac6fb3 100644
--- a/lib/Target/ARM/README.txt
+++ b/lib/Target/ARM/README.txt
@@ -17,24 +17,19 @@ Reimplement 'select' in terms of 'SEL'.
 
 //===---------------------------------------------------------------------===//
 
-The constant island pass has been much improved; all the todo items in the
-previous version of this document have been addressed.  However, there are still
-things that can be done:
-
-1.  When there isn't an existing water, the current MBB is split right after 
-the use.  It would be profitable to look farther forward, especially on Thumb,
-where negative offsets won't work.
-(Partially fixed:  it will put the island at the end of the block if that is 
-in range.  If it is not in range things still work as above, which is poor on 
-Thumb.)
-
-2.  There may be some advantage to trying to be smarter about the initial
+The constant island pass is in good shape.  Some cleanups might be desirable,
+but there is unlikely to be much improvement in the generated code.
+
+1.  There may be some advantage to trying to be smarter about the initial
 placement, rather than putting everything at the end.
 
-3.  The handling of 2-byte padding for Thumb is overly conservative.  There 
+2.  The handling of 2-byte padding for Thumb is overly conservative.  There 
 would be a small gain to keeping accurate track of the padding (which would
 require aligning functions containing constant pools to 4-byte boundaries).
 
+3.  There might be some compile-time efficiency to be had by representing
+consecutive islands as a single block rather than multiple blocks.
+
 //===---------------------------------------------------------------------===//
 
 We need to start generating predicated instructions.  The .td files have a way