LSR should avoid redundant edge splitting.

This handles the case in which LSR rewrites an IV user that is a phi and
splits critical edges originating from a switch.
Fixes <rdar://problem/6453893> LSR is not splitting edges "nicely"

llvm-svn: 141059

1 files changed, 43 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopStrengthReduce/2011-10-03-CritEdgeMerge.ll b/llvm/test/Transforms/LoopStrengthReduce/2011-10-03-CritEdgeMerge.ll
new file mode 100644
index 00000000000..a6996a81fb0
--- /dev/null
+++ b/llvm/test/Transforms/LoopStrengthReduce/2011-10-03-CritEdgeMerge.ll
@@ -0,0 +1,43 @@
+; RUN: opt -loop-reduce -S < %s | FileCheck %s
+;
+; Test LSR's use of SplitCriticalEdge during phi rewriting.
+; Verify that identical edges are merged. rdar://problem/6453893
+
+target triple = "x86-apple-darwin"
+
+; CHECK: @test
+; CHECK: bb89:
+; CHECK: phi i8* [ %lsr.iv.next1, %bbA.bb89_crit_edge ], [ %lsr.iv.next1, %bbB.bb89_crit_edge ]{{$}}
+
+define i8* @test() {
+entry:
+  br label %loop
+
+loop:
+  %rec = phi i32 [ %next, %loop ], [ 0, %entry ]
+  %next = add i32 %rec, 1
+  %tmp75 = getelementptr i8* null, i32 %next
+  br i1 false, label %loop, label %loopexit
+
+loopexit:
+  br i1 false, label %bbA, label %bbB
+
+bbA:
+  switch i32 0, label %bb89 [
+    i32 47, label %bb89
+    i32 58, label %bb89
+  ]
+
+bbB:
+  switch i8 0, label %bb89 [
+    i8 47, label %bb89
+    i8 58, label %bb89
+  ]
+
+bb89:
+  %tmp75phi = phi i8* [ %tmp75, %bbA ], [ %tmp75, %bbA ], [ %tmp75, %bbA ], [ %tmp75, %bbB ], [ %tmp75, %bbB ], [ %tmp75, %bbB ]
+  br label %exit
+
+exit:
+  ret i8* %tmp75phi
+}