[PATCH] Teach ScalarEvolution to use !range metadata.

[hfinkel at anl.gov]

Also, looking at this patch made me think: We don't handle range metadata in LazyValueInfo, do we? And we don't seem to, and I think your GetRangeFromMetadata will be useful for both cases. You might consider making it a general utility function somewhere.

================
Comment at: lib/Analysis/ScalarEvolution.cpp:3561
@@ +3560,3 @@
+    Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
+    if (MDRange.hasValue()) {
+      return setUnsignedRange(S, MDRange.getValue());
----------------
You don't need {} here.

================
Comment at: lib/Analysis/ScalarEvolution.cpp:3562
@@ +3561,3 @@
+    if (MDRange.hasValue()) {
+      return setUnsignedRange(S, MDRange.getValue());
+    }
----------------
More importantly, don't return here. ValueTracking might be able to refine the range even more, and we want the range information to be additive.

================
Comment at: lib/Analysis/ScalarEvolution.cpp:3718
@@ +3717,3 @@
+    Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
+    if (MDRange.hasValue()) {
+      return setSignedRange(S, MDRange.getValue());
----------------
Same comments apply here.

http://reviews.llvm.org/D5638