X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FTarget%2FARM%2FREADME.txt;h=2f6842e8cb6094f792fd25379883ae796d39aee8;hb=6248a546f23e7ffa84c171dc364b922e28467275;hp=8ba9a27e95c89251cc61e1d6a260fb644fde8cc0;hpb=acc9e7315c450ca7cffd4a65c65e578211f9d945;p=oota-llvm.git

diff --git a/lib/Target/ARM/README.txt b/lib/Target/ARM/README.txt
index 8ba9a27e95c..2f6842e8cb6 100644
--- a/lib/Target/ARM/README.txt
+++ b/lib/Target/ARM/README.txt
@@ -681,3 +681,21 @@ is compiled and optimized to:
     str    r1, [r0]
 
 //===---------------------------------------------------------------------===//
+
+Improve codegen for select's:
+if (x != 0) x = 1
+if (x == 1) x = 1
+
+ARM codegen used to look like this:
+       mov     r1, r0
+       cmp     r1, #1
+       mov     r0, #0
+       moveq   r0, #1
+
+The naive lowering select between two different values. It should recognize the
+test is equality test so it's more a conditional move rather than a select:
+       cmp     r0, #1
+       movne   r0, #0
+
+Currently this is a ARM specific dag combine. We probably should make it into a
+target-neutral one.