From 14ee003f1ae76cd6594a649e583717bfe92823a8 Mon Sep 17 00:00:00 2001
From: Chandler Carruth <chandlerc@gmail.com>
Date: Thu, 14 Aug 2014 01:07:37 +0000
Subject: [PATCH] [SDAG] Fix a case where we would iteratively legalize a node
 during combining by replacing it with something else but not re-process the
 node afterward to remove it.

In a truly remarkable stroke of bad luck, this would (in the test case
attached) end up getting some other node combined into it without ever
getting re-processed. By adding it back on to the worklist, in addition
to deleting the dead nodes more quickly we also ensure that if it
*stops* being dead for any reason it makes it back through the
legalizer. Without this, the test case will end up failing during
instruction selection due to an and node with a type we don't have an
instruction pattern for.

It took many million runs of the shuffle fuzz tester to find this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215611 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/LegalizeDAG.cpp   |  2 ++
 test/CodeGen/X86/vector-shuffle-128-v16.ll | 20 ++++++++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index d689630f72c..232cbd81f76 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -156,6 +156,8 @@ public:
   // Node replacement helpers
   void ReplacedNode(SDNode *N) {
     LegalizedNodes.erase(N);
+    if (UpdatedNodes)
+      UpdatedNodes->insert(N);
   }
   void ReplaceNode(SDNode *Old, SDNode *New) {
     DEBUG(dbgs() << " ... replacing: "; Old->dump(&DAG);
diff --git a/test/CodeGen/X86/vector-shuffle-128-v16.ll b/test/CodeGen/X86/vector-shuffle-128-v16.ll
index c168935134a..ad512402a33 100644
--- a/test/CodeGen/X86/vector-shuffle-128-v16.ll
+++ b/test/CodeGen/X86/vector-shuffle-128-v16.ll
@@ -269,3 +269,23 @@ define <16 x i8> @trunc_v4i32_shuffle(<16 x i8> %a) {
   %shuffle = shufflevector <16 x i8> %a, <16 x i8> undef, <16 x i32> <i32 0, i32 4, i32 8, i32 12, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef, i32 undef>
   ret <16 x i8> %shuffle
 }
+
+define <16 x i8> @stress_test0(<16 x i8> %s.0.1, <16 x i8> %s.0.2, <16 x i8> %s.0.3, <16 x i8> %s.0.4, <16 x i8> %s.0.5, <16 x i8> %s.0.6, <16 x i8> %s.0.7, <16 x i8> %s.0.8, <16 x i8> %s.0.9) {
+; We don't have anything useful to check here. This generates 100s of
+; instructions. Instead, just make sure we survived codegen.
+;
+; ALL-LABEL: @stress_test0
+; ALL: retq
+entry:
+  %s.1.4 = shufflevector <16 x i8> %s.0.4, <16 x i8> %s.0.5, <16 x i32> <i32 1, i32 22, i32 21, i32 28, i32 3, i32 16, i32 6, i32 1, i32 19, i32 29, i32 12, i32 31, i32 2, i32 3, i32 3, i32 6>
+  %s.1.5 = shufflevector <16 x i8> %s.0.5, <16 x i8> %s.0.6, <16 x i32> <i32 31, i32 20, i32 12, i32 19, i32 2, i32 15, i32 12, i32 31, i32 2, i32 28, i32 2, i32 30, i32 7, i32 8, i32 17, i32 28>
+  %s.1.8 = shufflevector <16 x i8> %s.0.8, <16 x i8> %s.0.9, <16 x i32> <i32 14, i32 10, i32 17, i32 5, i32 17, i32 9, i32 17, i32 21, i32 31, i32 24, i32 16, i32 6, i32 20, i32 28, i32 23, i32 8>
+  %s.2.2 = shufflevector <16 x i8> %s.0.3, <16 x i8> %s.0.4, <16 x i32> <i32 20, i32 9, i32 21, i32 11, i32 11, i32 4, i32 3, i32 18, i32 3, i32 30, i32 4, i32 31, i32 11, i32 24, i32 13, i32 29>
+  %s.3.2 = shufflevector <16 x i8> %s.2.2, <16 x i8> %s.1.4, <16 x i32> <i32 15, i32 13, i32 5, i32 11, i32 7, i32 17, i32 14, i32 22, i32 22, i32 16, i32 7, i32 24, i32 16, i32 22, i32 7, i32 29>
+  %s.5.4 = shufflevector <16 x i8> %s.1.5, <16 x i8> %s.1.8, <16 x i32> <i32 3, i32 13, i32 19, i32 7, i32 23, i32 11, i32 1, i32 9, i32 16, i32 25, i32 2, i32 7, i32 0, i32 21, i32 23, i32 17>
+  %s.6.1 = shufflevector <16 x i8> %s.3.2, <16 x i8> %s.3.2, <16 x i32> <i32 11, i32 2, i32 28, i32 31, i32 27, i32 3, i32 9, i32 27, i32 25, i32 25, i32 14, i32 7, i32 12, i32 28, i32 12, i32 23>
+  %s.7.1 = shufflevector <16 x i8> %s.6.1, <16 x i8> %s.3.2, <16 x i32> <i32 15, i32 29, i32 14, i32 0, i32 29, i32 15, i32 26, i32 30, i32 6, i32 7, i32 2, i32 8, i32 12, i32 10, i32 29, i32 17>
+  %s.7.2 = shufflevector <16 x i8> %s.3.2, <16 x i8> %s.5.4, <16 x i32> <i32 3, i32 29, i32 3, i32 19, i32 undef, i32 20, i32 undef, i32 3, i32 27, i32 undef, i32 undef, i32 11, i32 undef, i32 undef, i32 undef, i32 undef>
+  %s.16.0 = shufflevector <16 x i8> %s.7.1, <16 x i8> %s.7.2, <16 x i32> <i32 13, i32 1, i32 16, i32 16, i32 6, i32 7, i32 29, i32 18, i32 19, i32 28, i32 undef, i32 undef, i32 31, i32 1, i32 undef, i32 10>
+  ret <16 x i8> %s.16.0
+}