[llvm] r305070 - Prevent RemoveDeadNodes from deleted already deleted node.

[Nirav Dave via llvm-commits]

Author: niravd
Date: Fri Jun  9 07:57:35 2017
New Revision: 305070

URL: http://llvm.org/viewvc/llvm-project?rev=305070&view=rev
Log:
Prevent RemoveDeadNodes from deleted already deleted node.

This prevents against assertion errors like PR32659 which occur from a
replacement deleting a node after it's been added to the list argument
of RemoveDeadNodes. The specific failure from PR32659 does not
currently happen, but it is still potentially possible. The underlying
cause is that the callers of the change dfunction builds up a list of
nodes to delete after having moved their uses and it possible that a
move of a later node will cause a previously deleted nodes to be
deleted.

Reviewers: bkramer, spatel, davide

Reviewed By: spatel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D33731

Added:
    llvm/trunk/test/CodeGen/X86/pr32659.ll
Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp?rev=305070&r1=305069&r2=305070&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAG.cpp Fri Jun  9 07:57:35 2017
@@ -589,6 +589,11 @@ void SelectionDAG::RemoveDeadNodes(Small
   // worklist.
   while (!DeadNodes.empty()) {
     SDNode *N = DeadNodes.pop_back_val();
+    // Skip to next node if we've already managed to delete the node. This could
+    // happen if replacing a node causes a node previously added to the node to
+    // be deleted.
+    if (N->getOpcode() == ISD::DELETED_NODE)
+      continue;
 
     for (DAGUpdateListener *DUL = UpdateListeners; DUL; DUL = DUL->Next)
       DUL->NodeDeleted(N, nullptr);

Added: llvm/trunk/test/CodeGen/X86/pr32659.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr32659.ll?rev=305070&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pr32659.ll (added)
+++ llvm/trunk/test/CodeGen/X86/pr32659.ll Fri Jun  9 07:57:35 2017
@@ -0,0 +1,83 @@
+; RUN: llc -o - %s | FileCheck %s
+target datalayout = "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128"
+target triple = "i386-unknown-linux-gnu"
+
+ at a = external global i32, align 4
+ at d = external global i32*, align 4
+ at k = external global i32**, align 4
+ at j = external global i32***, align 4
+ at h = external global i32, align 4
+ at c = external global i32, align 4
+ at i = external global i32, align 4
+ at b = external global i32, align 4
+ at f = external global i64, align 8
+ at e = external global i64, align 8
+ at g = external global i32, align 4
+
+; Function Attrs: norecurse nounwind optsize readnone
+declare i32 @fn1(i32 returned) #0
+
+
+; CHECK-LABEL: fn2
+; CHECK: calll putchar
+; CHECK: addl $1,
+; CHECK: adcl $0,
+; Function Attrs: nounwind optsize
+define void @fn2() #1 {
+entry:
+  %putchar = tail call i32 @putchar(i32 48)
+  %0 = load volatile i32, i32* @h, align 4
+  %1 = load i32, i32* @c, align 4, !tbaa !2
+  %2 = load i32***, i32**** @j, align 4
+  %3 = load i32**, i32*** %2, align 4
+  %4 = load i32*, i32** %3, align 4
+  %5 = load i32, i32* %4, align 4
+  %cmp = icmp sgt i32 %1, %5
+  %conv = zext i1 %cmp to i32
+  %6 = load i32, i32* @i, align 4
+  %cmp1 = icmp sgt i32 %6, %conv
+  %conv2 = zext i1 %cmp1 to i32
+  store i32 %conv2, i32* @b, align 4
+  %cmp3 = icmp sgt i32 %0, %conv2
+  %conv4 = zext i1 %cmp3 to i32
+  %7 = load i32, i32* @a, align 4
+  %or = xor i32 %7, %conv4
+  store i32 %or, i32* @a, align 4
+  %8 = load i32*, i32** @d, align 4
+  %9 = load i32, i32* %8, align 4
+  %conv6 = sext i32 %9 to i64
+  %10 = load i64, i64* @e, align 8
+  %and = and i64 %10, %conv6
+  store i64 %and, i64* @e, align 8
+  %11 = load i32, i32* @g, align 4
+  %dec = add nsw i32 %11, -1
+  store i32 %dec, i32* @g, align 4
+  %12 = load i64, i64* @f, align 8
+  %inc = add nsw i64 %12, 1
+  store i64 %inc, i64* @f, align 8
+  ret void
+}
+
+; Function Attrs: nounwind optsize
+declare i32 @main() #1
+
+; Function Attrs: nounwind
+declare i32 @putchar(i32) #2
+
+attributes #0 = { optsize readnone }
+attributes #1 = { optsize }
+attributes #2 = { nounwind }
+
+!llvm.module.flags = !{!0}
+!llvm.ident = !{!1}
+
+!0 = !{i32 1, !"NumRegisterParameters", i32 0}
+!1 = !{!"clang version 5.0.0 (trunk 300074) (llvm/trunk 300078)"}
+!2 = !{!3, !3, i64 0}
+!3 = !{!"int", !4, i64 0}
+!4 = !{!"omnipotent char", !5, i64 0}
+!5 = !{!"Simple C/C++ TBAA"}
+!6 = !{!7, !7, i64 0}
+!7 = !{!"any pointer", !4, i64 0}
+!8 = !{!9, !9, i64 0}
+!9 = !{!"long long", !4, i64 0}