[PATCH] D46404: [DAG] Avoid using deleted node in rebuildSetCC
Nirav Dave via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Thu May 3 12:35:25 PDT 2018
niravd created this revision.
niravd added reviewers: dbabokin, RKSimon, eli.friedman, davide.
Herald added a subscriber: hiraditya.
The combine in rebuildSetCC may be combined to another
node leaving our references stale. Keep a handle on
it to avoid stale references.
Fixes PR36602.
Repository:
rL LLVM
https://reviews.llvm.org/D46404
Files:
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
llvm/test/CodeGen/X86/pr36602.ll
Index: llvm/test/CodeGen/X86/pr36602.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/pr36602.ll
@@ -0,0 +1,30 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+
+
+define i32 @fn2() {
+; CHECK-LABEL: fn2:
+; CHECK: # %bb.0:
+; CHECK-NEXT: xorl %eax, %eax
+; CHECK-NEXT: testb %al, %al
+; CHECK-NEXT: jne .LBB0_2
+; CHECK-NEXT: # %bb.1: # %bb1
+; CHECK-NEXT: xorl %eax, %eax
+; CHECK-NEXT: retq
+; CHECK-NEXT: .LBB0_2: # %bb2
+; CHECK-NEXT: movl $1, %eax
+; CHECK-NEXT: retq
+ %_tmp10 = icmp eq i8 0, 0
+ %_tmp13 = icmp slt i8 undef, 1
+ %_tmp151 = or i1 %_tmp10, %_tmp13
+ %_tmp15 = zext i1 %_tmp151 to i8
+ br i1 %_tmp151, label %bb1, label %bb2
+
+bb1: ; preds = %0, %0
+ ret i32 0
+
+bb2: ; preds = %0, %0
+ ret i32 1
+
+
+}
Index: llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -11498,16 +11498,22 @@
// Transform br(xor(x, y)) -> br(x != y)
// Transform br(xor(xor(x,y), 1)) -> br (x == y)
if (N.getOpcode() == ISD::XOR) {
- SDNode *TheXor = N.getNode();
+ while (N.getOpcode() == ISD::XOR) {
+ HandleSDNode XORHandle(N);
+ SDValue Tmp = visitXOR(N.getNode());
+ if (!Tmp.getNode())
+ break;
+ // In place update be a move.
+ if (Tmp.getNode() == N.getNode())
+ N = XORHandle.getValue();
+ else
+ N = Tmp;
+ }
- // Avoid missing important xor optimizations.
- while (SDValue Tmp = visitXOR(TheXor)) {
- // We don't have a XOR anymore, bail.
- if (Tmp.getOpcode() != ISD::XOR)
- return Tmp;
+ if (N.getOpcode() != ISD::XOR)
+ return N;
- TheXor = Tmp.getNode();
- }
+ SDNode *TheXor = N.getNode();
SDValue Op0 = TheXor->getOperand(0);
SDValue Op1 = TheXor->getOperand(1);
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