Factor the code for collecting IV users out of LSR into an IVUsers class,

and generalize it so that it can be used by IndVarSimplify. Implement the
base IndVarSimplify transformation code using IVUsers. This removes
TestOrigIVForWrap and associated code, as ScalarEvolution now has enough
builtin overflow detection and folding logic to handle all the same cases,
and more. Run "opt -iv-users -analyze -disable-output" on your favorite
loop for an example of what IVUsers does.

This lets IndVarSimplify eliminate IV casts and compute trip counts in
more cases. Also, this happens to finally fix the remaining testcases
in PR1301.

Now that IndVarSimplify is being more aggressive, it occasionally runs
into the problem where ScalarEvolutionExpander's code for avoiding
duplicate expansions makes it difficult to ensure that all expanded
instructions dominate all the instructions that will use them. As a
temporary measure, IndVarSimplify now uses a FixUsesBeforeDefs function
to fix up instructions inserted by SCEVExpander. Fortunately, this code
is contained, and can be easily removed once a more comprehensive
solution is available.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71535 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 0 insertions, 10 deletions

diff --git a/lib/Target/README.txt b/lib/Target/README.txt
index 538d1371a1..f68cf0e40d 100644
--- a/lib/Target/README.txt
+++ b/lib/Target/README.txt
@@ -749,16 +749,6 @@ be done safely if "b" isn't modified between the strlen and memcpy of course.
 
 //===---------------------------------------------------------------------===//
 
-We should be able to evaluate this loop:
-
-int test(int x_offs) {
-  while (x_offs > 4)
-     x_offs -= 4;
-  return x_offs;
-}
-
-//===---------------------------------------------------------------------===//
-
 Reassociate should turn things like:
 
 int factorial(int X) {