1 files changed, 25 insertions, 18 deletions
diff --git a/test/Analysis/ScalarEvolution/trip-count9.ll b/test/Analysis/ScalarEvolution/trip-count9.ll
index 9180f2b..85d4050 100644
--- a/test/Analysis/ScalarEvolution/trip-count9.ll
+++ b/test/Analysis/ScalarEvolution/trip-count9.ll
@@ -25,8 +25,8 @@ exit:
 }
 
 ; CHECK: Determining loop execution counts for: @step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
-; CHECK: Loop %loop: Unpredictable max backedge-taken count. 
+; CHECK: Loop %loop: Unpredictable backedge-taken count.
+; CHECK: Loop %loop: Unpredictable max backedge-taken count.
 define void @step2(i4 %n) {
 entry:
   %s = icmp sgt i4 %n, 0
@@ -57,8 +57,8 @@ exit:
 }
 
 ; CHECK: Determining loop execution counts for: @start1_step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
-; CHECK: Loop %loop: Unpredictable max backedge-taken count. 
+; CHECK: Loop %loop: Unpredictable backedge-taken count.
+; CHECK: Loop %loop: Unpredictable max backedge-taken count.
 define void @start1_step2(i4 %n) {
 entry:
   %s = icmp sgt i4 %n, 0
@@ -89,8 +89,8 @@ exit:
 }
 
 ; CHECK: Determining loop execution counts for: @startx_step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
-; CHECK: Loop %loop: Unpredictable max backedge-taken count. 
+; CHECK: Loop %loop: Unpredictable backedge-taken count.
+; CHECK: Loop %loop: Unpredictable max backedge-taken count.
 define void @startx_step2(i4 %n, i4 %x) {
 entry:
   %s = icmp sgt i4 %n, 0
@@ -120,12 +120,18 @@ exit:
   ret void
 }
 
-; Be careful with this one. If %n is INT4_MAX, %i.next will wrap. The nsw bit
-; says that the result is undefined, but ScalarEvolution must respect that
-; subsequent passes may result the undefined behavior in predictable ways.
+; If %n is INT4_MAX, %i.next will wrap. The nsw bit says that the
+; result is undefined. Therefore, after the loop's second iteration,
+; we are free to assume that the loop exits. This is valid because:
+; (a) %i.next is a poison value after the second iteration, which can
+; also be considered an undef value.
+; (b) the return instruction enacts a side effect that is control
+; dependent on the poison value.
+;
+; CHECK-LABEL: nsw_step2
 ; CHECK: Determining loop execution counts for: @nsw_step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
-; CHECK: Loop %loop: Unpredictable max backedge-taken count. 
+; CHECK: Loop %loop: backedge-taken count is ((-1 + %n) /u 2)
+; CHECK: Loop %loop: max backedge-taken count is 2
 define void @nsw_step2(i4 %n) {
 entry:
   %s = icmp sgt i4 %n, 0
@@ -139,6 +145,7 @@ exit:
   ret void
 }
 
+; CHECK-LABEL: nsw_start1
 ; CHECK: Determining loop execution counts for: @nsw_start1
 ; CHECK: Loop %loop: backedge-taken count is (-2 + (2 smax %n))
 ; CHECK: Loop %loop: max backedge-taken count is 5
@@ -156,8 +163,8 @@ exit:
 }
 
 ; CHECK: Determining loop execution counts for: @nsw_start1_step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
-; CHECK: Loop %loop: Unpredictable max backedge-taken count. 
+; CHECK: Loop %loop: backedge-taken count is ((-2 + (3 smax %n)) /u 2)
+; CHECK: Loop %loop: max backedge-taken count is 2
 define void @nsw_start1_step2(i4 %n) {
 entry:
   %s = icmp sgt i4 %n, 0
@@ -188,8 +195,8 @@ exit:
 }
 
 ; CHECK: Determining loop execution counts for: @nsw_startx_step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
-; CHECK: Loop %loop: Unpredictable max backedge-taken count. 
+; CHECK: Loop %loop: backedge-taken count is ((-1 + (-1 * %x) + ((2 + %x) smax %n)) /u 2)
+; CHECK: Loop %loop: max backedge-taken count is 7
 define void @nsw_startx_step2(i4 %n, i4 %x) {
 entry:
   %s = icmp sgt i4 %n, 0
@@ -221,7 +228,7 @@ exit:
 }
 
 ; CHECK: Determining loop execution counts for: @even_step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
+; CHECK: Loop %loop: Unpredictable backedge-taken count.
 ; CHECK: Loop %loop: max backedge-taken count is 2
 define void @even_step2(i4 %n) {
 entry:
@@ -255,7 +262,7 @@ exit:
 }
 
 ; CHECK: Determining loop execution counts for: @even_start1_step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
+; CHECK: Loop %loop: Unpredictable backedge-taken count.
 ; CHECK: Loop %loop: max backedge-taken count is 2
 define void @even_start1_step2(i4 %n) {
 entry:
@@ -289,7 +296,7 @@ exit:
 }
 
 ; CHECK: Determining loop execution counts for: @even_startx_step2
-; CHECK: Loop %loop: Unpredictable backedge-taken count. 
+; CHECK: Loop %loop: Unpredictable backedge-taken count.
 ; CHECK: Loop %loop: max backedge-taken count is 7
 define void @even_startx_step2(i4 %n, i4 %x) {
 entry: