[PATCH] D48364: [DAG] Don't map a TableId to itself in the ReplacedValues map

[Bjorn Pettersson via Phabricator via llvm-commits]

bjope created this revision.
bjope added a reviewer: niravd.

Found some regressions (infinite loop in DAGTypeLegalizer::RemapId)
after r334880. This patch makes sure that we do map a TableId to
itself.


Repository:
  rL LLVM

https://reviews.llvm.org/D48364

Files:
  lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
  lib/CodeGen/SelectionDAG/LegalizeTypes.h
  test/CodeGen/X86/legalize-types-remapid.ll


Index: test/CodeGen/X86/legalize-types-remapid.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/legalize-types-remapid.ll
@@ -0,0 +1,16 @@
+; RUN: llc -mtriple=i386 -mcpu=generic -O0 -o /dev/null %s
+
+ at c = global i32 0
+ at d = global <2 x i64> zeroinitializer
+
+define void @test() {
+bb1:
+  %t0 = load <2 x i64>, <2 x i64>* @d
+  %t0.i0 = extractelement <2 x i64> %t0, i32 0
+  %t0.i0.cast = bitcast i64 %t0.i0 to <2 x i32>
+  %t0.i0.cast.i0 = extractelement <2 x i32> %t0.i0.cast, i32 0
+  store volatile i32 %t0.i0.cast.i0, i32* @c
+  %t0.i0.cast.i1 = extractelement <2 x i32> %t0.i0.cast, i32 1
+  store volatile i32 %t0.i0.cast.i1, i32* @c
+  ret void
+}
Index: lib/CodeGen/SelectionDAG/LegalizeTypes.h
===================================================================
--- lib/CodeGen/SelectionDAG/LegalizeTypes.h
+++ lib/CodeGen/SelectionDAG/LegalizeTypes.h
@@ -186,7 +186,8 @@
       TableId NewId = getTableId(SDValue(New, i));
       TableId OldId = getTableId(SDValue(Old, i));
 
-      ReplacedValues[OldId] = NewId;
+      if (OldId != NewId)
+        ReplacedValues[OldId] = NewId;
 
       // Delete Node from tables.
       ValueToIdMap.erase(SDValue(Old, i));
Index: lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
+++ lib/CodeGen/SelectionDAG/LegalizeTypes.cpp
@@ -575,6 +575,7 @@
 void DAGTypeLegalizer::RemapId(TableId &Id) {
   auto I = ReplacedValues.find(Id);
   if (I != ReplacedValues.end()) {
+    assert(Id != I->second && "Id is mapped to itself.");
     // Use path compression to speed up future lookups if values get multiply
     // replaced with other values.
     RemapId(I->second);
@@ -652,7 +653,8 @@
     auto FromId = getTableId(From);
     auto ToId = getTableId(To);
 
-    ReplacedValues[FromId] = ToId;
+    if (FromId != ToId)
+      ReplacedValues[FromId] = ToId;
     DAG.ReplaceAllUsesOfValueWith(From, To);
 
     // Process the list of nodes that need to be reanalyzed.
@@ -685,7 +687,8 @@
           auto OldValId = getTableId(OldVal);
           auto NewValId = getTableId(NewVal);
           DAG.ReplaceAllUsesOfValueWith(OldVal, NewVal);
-          ReplacedValues[OldValId] = NewValId;
+          if (OldValId != NewValId)
+            ReplacedValues[OldValId] = NewValId;
         }
         // The original node continues to exist in the DAG, marked NewNode.
       }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D48364.152074.patch
Type: text/x-patch
Size: 2492 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20180620/c1efcbf4/attachment.bin>