From d7bfd0028b273f2e3935e8c7ff95db6fa2b21789 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Fri, 2 Apr 2010 14:48:31 +0000
Subject: [PATCH] Manually notify ScalarEvolution before making an operand
 replacement, since it can't currently observe such changes automatically.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100186 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/IndVarSimplify.cpp      |  7 ++++
 .../Transforms/IndVarSimplify/dangling-use.ll | 41 +++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 test/Transforms/IndVarSimplify/dangling-use.ll

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index 988a4cb3f2a..2722a66aebf 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -510,6 +510,13 @@ void IndVarSimplify::RewriteIVExpressions(Loop *L, SCEVExpander &Rewriter) {
     // Now expand it into actual Instructions and patch it into place.
     Value *NewVal = Rewriter.expandCodeFor(AR, UseTy, InsertPt);
 
+    // Inform ScalarEvolution that this value is changing. The change doesn't
+    // affect its value, but it does potentially affect which use lists the
+    // value will be on after the replacement, which affects ScalarEvolution's
+    // ability to walk use lists and drop dangling pointers when a value is
+    // deleted.
+    SE->forgetValue(User);
+
     // Patch the new value into place.
     if (Op->hasName())
       NewVal->takeName(Op);
diff --git a/test/Transforms/IndVarSimplify/dangling-use.ll b/test/Transforms/IndVarSimplify/dangling-use.ll
new file mode 100644
index 00000000000..51c31204c6d
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/dangling-use.ll
@@ -0,0 +1,41 @@
+; RUN: opt -indvars -disable-output < %s 
+
+target datalayout = "E-p:32:32:32-i1:8:8-i8:8:8-i8:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f128:64:128-n32"
+target triple = "powerpc-apple-darwin11"
+
+define void @vec_inverse_5_7_vert_loop_copyseparate(i8* %x, i32 %n, i32 %rowbytes) nounwind {
+entry:
+  %tmp1 = sdiv i32 %n, 3                          ; <i32> [#uses=1]
+  %tmp2 = sdiv i32 %rowbytes, 5                   ; <i32> [#uses=2]
+  br label %bb49
+
+bb49:                                             ; preds = %bb48, %entry
+  %x_addr.0 = phi i8* [ %x, %entry ], [ %tmp481, %bb48 ] ; <i8*> [#uses=2]
+  br label %bb10
+
+bb10:                                             ; preds = %bb49
+  %tmp326 = mul nsw i32 %tmp1, %tmp2              ; <i32> [#uses=1]
+  %tmp351 = getelementptr inbounds i8* %x_addr.0, i32 %tmp326 ; <i8*> [#uses=1]
+  br i1 false, label %bb.nph, label %bb48
+
+bb.nph:                                           ; preds = %bb10
+  br label %bb23
+
+bb23:                                             ; preds = %bb28, %bb.nph
+  %pOriginHi.01 = phi i8* [ %tmp351, %bb.nph ], [ %pOriginHi.0, %bb28 ] ; <i8*> [#uses=2]
+  %tmp378 = bitcast i8* %pOriginHi.01 to i8*      ; <i8*> [#uses=1]
+  store i8* %tmp378, i8** null
+  %tmp385 = getelementptr inbounds i8* %pOriginHi.01, i32 %tmp2 ; <i8*> [#uses=1]
+  br label %bb28
+
+bb28:                                             ; preds = %bb23
+  %pOriginHi.0 = phi i8* [ %tmp385, %bb23 ]       ; <i8*> [#uses=1]
+  br i1 false, label %bb23, label %bb28.bb48_crit_edge
+
+bb28.bb48_crit_edge:                              ; preds = %bb28
+  br label %bb48
+
+bb48:                                             ; preds = %bb28.bb48_crit_edge, %bb10
+  %tmp481 = getelementptr inbounds i8* %x_addr.0, i32 1 ; <i8*> [#uses=1]
+  br label %bb49
+}
-- 
2.34.1