[PATCH] D34095: [DAG] Prevent CombineTo from deleting already deleted nodes

[Nirav Dave via Phabricator via llvm-commits]

niravd created this revision.

In combine passes where multiple nodes are updated, it is possible for
an to-be-replaced node to be deleted and from a previous CombineTo
call.  This causes a spurious node deletion. Add a check to
prevent such deletions.

Fixes PR32515.


https://reviews.llvm.org/D34095

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/X86/pr32515.ll


Index: test/CodeGen/X86/pr32515.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/pr32515.ll
@@ -0,0 +1,29 @@
+; RUN: llc -O0 -mtriple=x86_64-unknown -mcpu=skx -o - %s
+; RUN: llc     -mtriple=x86_64-unknown -mcpu=skx -o - %s
+; RUN: llc -O0 -mtriple=i686-unknown   -mcpu=skx -o - %s
+; RUN: llc     -mtriple=i686-unknown   -mcpu=skx -o - %s
+; REQUIRES: asserts
+
+ at var_26 = external global i16, align 2
+
+define void @foo() #0 {
+ %1 = alloca i16, align 2
+ %2 = load i16, i16* @var_26, align 2
+ %3 = zext i16 %2 to i32
+ %4 = icmp ne i32 %3, 7
+ %5 = zext i1 %4 to i16
+ store i16 %5, i16* %1, align 2
+ %6 = load i16, i16* @var_26, align 2
+ %7 = zext i16 %6 to i32
+ %8 = and i32 1, %7
+ %9 = shl i32 %8, 0
+ %10 = load i16, i16* @var_26, align 2
+ %11 = zext i16 %10 to i32
+ %12 = icmp ne i32 %11, 7
+ %13 = zext i1 %12 to i32
+ %14 = and i32 %9, %13
+ %15 = icmp ne i32 %14, 0
+ %16 = zext i1 %15 to i8
+ store i8 %16, i8* undef, align 1
+ unreachable
+ }
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -945,7 +945,7 @@
   // Finally, if the node is now dead, remove it from the graph.  The node
   // may not be dead if the replacement process recursively simplified to
   // something else needing this node.
-  if (N->use_empty())
+  if (N->use_empty() && N->getOpcode() != ISD::DELETED_NODE)
     deleteAndRecombine(N);
   return SDValue(N, 0);
 }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D34095.102145.patch
Type: text/x-patch
Size: 1580 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170611/85932484/attachment.bin>