[PATCH] D141256: [DAGCombine]Don't check for Undef/Poison if the node is deleted

Zhang via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Mon Jan 9 17:57:31 PST 2023


Naville updated this revision to Diff 487627.
Naville added a comment.

Address review issues


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D141256/new/

https://reviews.llvm.org/D141256

Files:
  llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  llvm/test/CodeGen/AArch64/dagcombine-deleted-freeze.ll


Index: llvm/test/CodeGen/AArch64/dagcombine-deleted-freeze.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AArch64/dagcombine-deleted-freeze.ll
@@ -0,0 +1,15 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=aarch64 | FileCheck %s
+define i8 @f(i64 %0) {
+; CHECK-LABEL: f:
+; CHECK:       // %bb.0:
+; CHECK-NEXT:    mov w0, wzr
+; CHECK-NEXT:    ret
+  %2 = freeze i64 %0
+  %3 = trunc i64 %2 to i1
+  %4 = trunc i64 %0 to i1
+  %5 = xor i1 %3, %4
+  %6 = freeze i1 %5
+  %7 = zext i1 %6 to i8
+  ret i8 %7
+}
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -14341,6 +14341,13 @@
                              MaybePoisonOperand);
     }
   }
+  // Early-out if the node has already been updated in place.
+  if(N0.getOpcode() == ISD::DELETED_NODE)
+    return SDValue();
+
+  // The whole node may have been updated, so the value we were holding
+  // may no longer be valid. Re-fetch the operand we're `freeze`ing.
+  N0 = N->getOperand(0);
 
   // Finally, recreate the node, it's operands were updated to use
   // frozen operands, so we just need to use it's "original" operands.


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