[PATCH] D37547: [X86] Call removeDeadNode when we're done doing custom isel for mul, div and test

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.

Once we've done our custom isel for these nodes, I think we should be calling removeDeadNode to prune them out of the DAG. Table driven isel ultimately either calls morphNodeTo which modifies a node and doesn't leave dead nodes. Or it emits new nodes and then calls removeDeadNode as part of Opc_CompleteMatch.

If you run a simple multiply test case like this through llc with -debug you'll see a umul_lohi node get printed as part of the dump for Instruction Selection ends.

  define i64 @foo(i64 %a, i64 %b) local_unnamed_addr #0 {
  entry:
    %conv = zext i64 %a to i128
    %conv1 = zext i64 %b to i128
    %mul = mul nuw nsw i128 %conv1, %conv
    %shr = lshr i128 %mul, 64
    %conv2 = trunc i128 %shr to i64
    ret i64 %conv2
  }


https://reviews.llvm.org/D37547

Files:
  lib/Target/X86/X86ISelDAGToDAG.cpp


Index: lib/Target/X86/X86ISelDAGToDAG.cpp
===================================================================
--- lib/Target/X86/X86ISelDAGToDAG.cpp
+++ lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -2455,6 +2455,7 @@
       DEBUG(dbgs() << "=> "; ResHi.getNode()->dump(CurDAG); dbgs() << '\n');
     }
 
+    CurDAG->RemoveDeadNode(Node);
     return;
   }
 
@@ -2639,6 +2640,7 @@
       ReplaceUses(SDValue(Node, 1), Result);
       DEBUG(dbgs() << "=> "; Result.getNode()->dump(CurDAG); dbgs() << '\n');
     }
+    CurDAG->RemoveDeadNode(Node);
     return;
   }
 
@@ -2697,6 +2699,7 @@
         // one, do not call ReplaceAllUsesWith.
         ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
                     SDValue(NewNode, 0));
+        CurDAG->RemoveDeadNode(Node);
         return;
       }
 
@@ -2732,6 +2735,7 @@
         // one, do not call ReplaceAllUsesWith.
         ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
                     SDValue(NewNode, 0));
+        CurDAG->RemoveDeadNode(Node);
         return;
       }
 
@@ -2752,6 +2756,7 @@
         // one, do not call ReplaceAllUsesWith.
         ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
                     SDValue(NewNode, 0));
+        CurDAG->RemoveDeadNode(Node);
         return;
       }
 
@@ -2772,6 +2777,7 @@
         // one, do not call ReplaceAllUsesWith.
         ReplaceUses(SDValue(Node, (Opcode == X86ISD::SUB ? 1 : 0)),
                     SDValue(NewNode, 0));
+        CurDAG->RemoveDeadNode(Node);
         return;
       }
     }


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D37547.114111.patch
Type: text/x-patch
Size: 1566 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20170907/6f2494f5/attachment.bin>