Revert "Temporarily Revert "Add basic loop fusion pass.""
The reversion apparently deleted the test/Transforms directory.
Will be re-reverting again.
llvm-svn: 358552
diff --git a/llvm/test/Transforms/LoopStrengthReduce/scev-after-loopinstsimplify.ll b/llvm/test/Transforms/LoopStrengthReduce/scev-after-loopinstsimplify.ll
new file mode 100644
index 0000000..a0dcaad
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/scev-after-loopinstsimplify.ll
@@ -0,0 +1,43 @@
+; RUN: opt %s -indvars -loop-instsimplify -loop-reduce
+; We are only checking that there is no crash!
+
+; https://bugs.llvm.org/show_bug.cgi?id=37936
+
+; The problem is as follows:
+; 1. indvars marks %dec as NUW.
+; 2. loop-instsimplify runs instsimplify, which constant-folds %dec to -1
+; 3. loop-reduce tries to do some further modification, but crashes
+; with an type assertion in cast, because %dec is no longer an Instruction,
+; even though the SCEV data indicated it was.
+
+; If the runline is split into two, i.e. -indvars -loop-instsimplify first, that
+; stored into a file, and then -loop-reduce is run on that, there is no crash.
+; So it looks like the problem is due to -loop-instsimplify not discarding SCEV.
+
+target datalayout = "n16"
+
+@a = external global i16, align 1
+
+define void @f1() {
+entry:
+ br label %for.cond
+
+for.cond: ; preds = %land.end, %entry
+ %c.0 = phi i16 [ 0, %entry ], [ %dec, %land.end ]
+ br i1 undef, label %for.body, label %for.cond.cleanup
+
+for.cond.cleanup: ; preds = %for.cond
+ ret void
+
+for.body: ; preds = %for.cond
+ %0 = load i16, i16* @a, align 1
+ %cmp = icmp sgt i16 %0, %c.0
+ br i1 %cmp, label %land.rhs, label %land.end
+
+land.rhs: ; preds = %for.body
+ unreachable
+
+land.end: ; preds = %for.body
+ %dec = add nsw i16 %c.0, -1
+ br label %for.cond
+}