Teach ScalarEvolution how to compute a tripcount for a loop with

true or false as its exit condition. These are usually eliminated by
SimplifyCFG, but the may be left around during a pass which wishes
to preserve the CFG.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@96683 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 76 insertions, 0 deletions

diff --git a/test/Analysis/ScalarEvolution/trip-count10.ll b/test/Analysis/ScalarEvolution/trip-count10.ll
new file mode 100644
index 0000000..0a992f9
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/trip-count10.ll
@@ -0,0 +1,76 @@
+; RUN: opt < %s -analyze -scalar-evolution | FileCheck %s
+
+; Trip counts with trivial exit conditions.
+
+; CHECK: Determining loop execution counts for: @a
+; CHECK: Loop %loop: Unpredictable backedge-taken count. 
+; CHECK: Loop %loop: Unpredictable max backedge-taken count.
+
+; CHECK: Determining loop execution counts for: @b
+; CHECK: Loop %loop: backedge-taken count is false
+; CHECK: Loop %loop: max backedge-taken count is false
+
+; CHECK: Determining loop execution counts for: @c
+; CHECK: Loop %loop: backedge-taken count is false
+; CHECK: Loop %loop: max backedge-taken count is false
+
+; CHECK: Determining loop execution counts for: @d
+; CHECK: Loop %loop: Unpredictable backedge-taken count. 
+; CHECK: Loop %loop: Unpredictable max backedge-taken count. 
+
+define void @a(i64 %n) nounwind {
+entry:
+  %t0 = icmp sgt i64 %n, 0
+  br i1 %t0, label %loop, label %return
+
+loop:
+  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+  %i.next = add nsw i64 %i, 1
+  %exitcond = icmp eq i64 %i.next, %n
+  br i1 false, label %return, label %loop
+
+return:
+  ret void
+}
+define void @b(i64 %n) nounwind {
+entry:
+  %t0 = icmp sgt i64 %n, 0
+  br i1 %t0, label %loop, label %return
+
+loop:
+  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+  %i.next = add nsw i64 %i, 1
+  %exitcond = icmp eq i64 %i.next, %n
+  br i1 true, label %return, label %loop
+
+return:
+  ret void
+}
+define void @c(i64 %n) nounwind {
+entry:
+  %t0 = icmp sgt i64 %n, 0
+  br i1 %t0, label %loop, label %return
+
+loop:
+  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+  %i.next = add nsw i64 %i, 1
+  %exitcond = icmp eq i64 %i.next, %n
+  br i1 false, label %loop, label %return
+
+return:
+  ret void
+}
+define void @d(i64 %n) nounwind {
+entry:
+  %t0 = icmp sgt i64 %n, 0
+  br i1 %t0, label %loop, label %return
+
+loop:
+  %i = phi i64 [ %i.next, %loop ], [ 0, %entry ]
+  %i.next = add nsw i64 %i, 1
+  %exitcond = icmp eq i64 %i.next, %n
+  br i1 true, label %loop, label %return
+
+return:
+  ret void
+}