[LoopRerolling] Be more forgiving with instruction order.

We can't solve the full subgraph isomorphism problem. But we can
allow obvious cases, where for example two instructions of different
types are out of order. Due to them having different types/opcodes,
there is no ambiguity.

llvm-svn: 228931

1 files changed, 57 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopReroll/basic.ll b/llvm/test/Transforms/LoopReroll/basic.ll
index 92bf2946be2..f30f417f17a 100644
--- a/llvm/test/Transforms/LoopReroll/basic.ll
+++ b/llvm/test/Transforms/LoopReroll/basic.ll
@@ -488,6 +488,63 @@ for.end:                                          ; preds = %for.body
   ret void
 }
 
+; int foo(int a);
+; void bar2(int *x, int y, int z) {
+;   for (int i = 0; i < 500; i += 3) {
+;     foo(i+y+i*z); // Slightly reordered instruction order
+;     foo(i+1+y+(i+1)*z);
+;     foo(i+2+y+(i+2)*z);
+;   }
+; }
+
+; Function Attrs: nounwind uwtable
+define void @bar2(i32* nocapture readnone %x, i32 %y, i32 %z) #0 {
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %for.body, %entry
+  %i.08 = phi i32 [ 0, %entry ], [ %add3, %for.body ]
+
+  %tmp1 = add i32 %i.08, %y
+  %tmp2 = mul i32 %i.08, %z
+  %tmp3 = add i32 %tmp2, %tmp1
+  %call = tail call i32 @foo(i32 %tmp3) #1
+
+  %add = add nsw i32 %i.08, 1
+  %tmp2a = mul i32 %add, %z
+  %tmp1a = add i32 %add, %y
+  %tmp3a = add i32 %tmp2a, %tmp1a
+  %calla = tail call i32 @foo(i32 %tmp3a) #1
+  
+  %add2 = add nsw i32 %i.08, 2
+  %tmp2b = mul i32 %add2, %z
+  %tmp1b = add i32 %add2, %y
+  %tmp3b = add i32 %tmp2b, %tmp1b
+  %callb = tail call i32 @foo(i32 %tmp3b) #1
+
+  %add3 = add nsw i32 %i.08, 3
+
+  %exitcond = icmp eq i32 %add3, 500
+  br i1 %exitcond, label %for.end, label %for.body
+
+; CHECK-LABEL: @bar2
+
+; CHECK: for.body:
+; CHECK: %indvar = phi i32 [ %indvar.next, %for.body ], [ 0, %entry ]
+; CHECK: %tmp1 = add i32 %indvar, %y
+; CHECK: %tmp2 = mul i32 %indvar, %z
+; CHECK: %tmp3 = add i32 %tmp2, %tmp1
+; CHECK: %call = tail call i32 @foo(i32 %tmp3) #1
+; CHECK: %indvar.next = add i32 %indvar, 1
+; CHECK: %exitcond1 = icmp eq i32 %indvar, 497
+; CHECK: br i1 %exitcond1, label %for.end, label %for.body
+
+; CHECK: ret
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
 
 attributes #0 = { nounwind uwtable }
 attributes #1 = { nounwind }