[SCEV] Unify getUnsignedRange and getSignedRange

Summary:
This removes some duplicated code, and also helps optimization: e.g. in
the test case added, `%idx ULT 128` in `@x` is not currently optimized
to `true` by `-indvars` but will be, after this change.

The only functional change in ths commit is that for add recurrences,
ScalarEvolution::getRange will be more aggressive -- computing the
unsigned (resp. signed) range for a SCEVAddRecExpr will now look at the
NSW (resp. NUW) bits and check for signed (resp. unsigned) overflow.
This can be a strict improvement in some cases (such as the attached
test case), and should be no worse in other cases.

Reviewers: atrick, nlewycky

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8142

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@231709 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 39 insertions, 0 deletions

diff --git a/test/Analysis/ScalarEvolution/range-signedness.ll b/test/Analysis/ScalarEvolution/range-signedness.ll
new file mode 100644
index 00000000000..d04fc9eb56b
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/range-signedness.ll
@@ -0,0 +1,39 @@
+; RUN: opt -analyze -scalar-evolution < %s | FileCheck %s
+
+define void @x(i1* %cond) {
+; CHECK-LABEL: Classifying expressions for: @x
+ entry:
+  br label %loop
+
+ loop:
+  %idx = phi i8 [ 0, %entry ], [ %idx.inc, %loop ]
+; CHECK: %idx = phi i8 [ 0, %entry ], [ %idx.inc, %loop ]
+; CHECK-NEXT:  -->  {0,+,1}<nuw><nsw><%loop> U: [0,-128) S: [0,-128)
+
+  %idx.inc = add nsw i8 %idx, 1
+
+  %c = load volatile i1, i1* %cond
+  br i1 %c, label %loop, label %exit
+
+ exit:
+  ret void
+}
+
+define void @y(i8* %addr) {
+; CHECK-LABEL: Classifying expressions for: @y
+ entry:
+  br label %loop
+
+ loop:
+  %idx = phi i8 [-5, %entry ], [ %idx.inc, %loop ]
+; CHECK:   %idx = phi i8 [ -5, %entry ], [ %idx.inc, %loop ]
+; CHECK-NEXT:  -->  {-5,+,1}<%loop> U: [-5,6) S: [-5,6)
+
+  %idx.inc = add i8 %idx, 1
+
+  %continue = icmp slt i8 %idx.inc, 6
+  br i1 %continue, label %loop, label %exit
+
+ exit:
+  ret void
+}