Prep for merging 3.4: Undo changes from 3.3 branch

test/Transforms/LoopUnroll/scevunroll.ll

 ; RUN: opt < %s -S -indvars -loop-unroll -verify-loop-info | FileCheck %s
 ;
 ; Unit tests for loop unrolling using ScalarEvolution to compute trip counts.
 ;
 ; Indvars is run first to generate an "old" SCEV result. Some unit
 ; tests may check that SCEV is properly invalidated between passes.
 
 ; Completely unroll loops without a canonical IV.
 ;
 ; CHECK: @sansCanonical
@@ skipping 48 matching lines @@
 
 exit1:
   ret i64 %s
 
 exit2:
   ret i64 %s.next
 }
 
 ; SCEV properly unrolls multi-exit loops.
 ;
-; SCEV cannot currently unroll this loop.
-; It should ideally detect a trip count of 5.
-; rdar:14038809 [SCEV]: Optimize trip count computation for multi-exit loops.
 ; CHECK: @multiExit
-; CHECKFIXME: getelementptr i32* %base, i32 10
-; CHECKFIXME-NEXT: load i32*
-; CHECKFIXME: br i1 false, label %l2.10, label %exit1
-; CHECKFIXME: l2.10:
-; CHECKFIXME-NOT: br
-; CHECKFIXME: ret i32
+; CHECK: getelementptr i32* %base, i32 10
+; CHECK-NEXT: load i32*
+; CHECK: br i1 false, label %l2.10, label %exit1
+; CHECK: l2.10:
+; CHECK-NOT: br
+; CHECK: ret i32
 define i32 @multiExit(i32* %base) nounwind {
 entry:
   br label %l1
 l1:
   %iv1 = phi i32 [ 0, %entry ], [ %inc1, %l2 ]
   %iv2 = phi i32 [ 0, %entry ], [ %inc2, %l2 ]
   %inc1 = add i32 %iv1, 1
   %inc2 = add i32 %iv2, 1
   %adr = getelementptr i32* %base, i32 %iv1
   %val = load i32* %adr
@@ skipping 77 matching lines @@
   %inc76 = add nsw i32 %i.113, 1
   br i1 false, label %for.body38, label %for.body87.preheader
 
 for.body87.preheader:
   br label %for.body87
 
 for.body87:
   br label %for.body87
 }
 
-; PR16130: clang produces incorrect code with loop/expression at -O2
-; rdar:14036816 loop-unroll makes assumptions about undefined behavior
-;
-; The loop latch is assumed to exit after the first iteration because
-; of the induction variable's NSW flag. However, the loop latch's
-; equality test is skipped and the loop exits after the second
-; iteration via the early exit. So loop unrolling cannot assume that
-; the loop latch's exit count of zero is an upper bound on the number
-; of iterations.
-;
-; CHECK: @nsw_latch
-; CHECK: for.body:
-; CHECK: %b.03 = phi i32 [ 0, %entry ], [ %add, %for.cond ]
-; CHECK: return:
-; CHECK: %b.03.lcssa = phi i32 [ %b.03, %for.body ], [ %b.03, %for.cond ]
-define void @nsw_latch(i32* %a) nounwind {
-entry:
-  br label %for.body
-
-for.body:                                         ; preds = %for.cond, %entry
-  %b.03 = phi i32 [ 0, %entry ], [ %add, %for.cond ]
-  %tobool = icmp eq i32 %b.03, 0
-  %add = add nsw i32 %b.03, 8
-  br i1 %tobool, label %for.cond, label %return
-
-for.cond:                                         ; preds = %for.body
-  %cmp = icmp eq i32 %add, 13
-  br i1 %cmp, label %return, label %for.body
-
-return:                                           ; preds = %for.body, %for.cond
-  %b.03.lcssa = phi i32 [ %b.03, %for.body ], [ %b.03, %for.cond ]
-  %retval.0 = phi i32 [ 1, %for.body ], [ 0, %for.cond ]
-  store i32 %b.03.lcssa, i32* %a, align 4
-  ret void
-}