release/21.x: [PowerPC] Avoid working on deleted node in ext bool trunc combine (#160050)

[llvmbot]

Backport 8b824f3

Requested by: @nikic

[llvmbot]

@RolandF77 What do you think about merging this PR to the release branch?

[llvmbot]

@llvm/pr-subscribers-backend-powerpc

Author: None (llvmbot)

Changes

Backport 8b824f3

Requested by: @nikic

---

Full diff: https://github.com/llvm/llvm-project/pull/160187.diff

2 Files Affected:

• (modified) llvm/lib/Target/PowerPC/PPCISelLowering.cpp (+6-4)
• (added) llvm/test/CodeGen/PowerPC/pr160040.ll (+24)

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 67f59ed507f38..b6db0abcc86d0 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -15327,6 +15327,12 @@ SDValue PPCTargetLowering::DAGCombineExtBoolTrunc(SDNode *N,
     }
   }
 
+  // Convert PromOps to handles before doing any RAUW operations, as these
+  // may CSE with existing nodes, deleting the originals.
+  std::list<HandleSDNode> PromOpHandles;
+  for (auto &PromOp : PromOps)
+    PromOpHandles.emplace_back(PromOp);
+
   // Replace all inputs, either with the truncation operand, or a
   // truncation or extension to the final output type.
   for (unsigned i = 0, ie = Inputs.size(); i != ie; ++i) {
@@ -15350,10 +15356,6 @@ SDValue PPCTargetLowering::DAGCombineExtBoolTrunc(SDNode *N,
         DAG.getAnyExtOrTrunc(InSrc, dl, N->getValueType(0)));
   }
 
-  std::list<HandleSDNode> PromOpHandles;
-  for (auto &PromOp : PromOps)
-    PromOpHandles.emplace_back(PromOp);
-
   // Replace all operations (these are all the same, but have a different
   // (promoted) return type). DAG.getNode will validate that the types of
   // a binary operator match, so go through the list in reverse so that
diff --git a/llvm/test/CodeGen/PowerPC/pr160040.ll b/llvm/test/CodeGen/PowerPC/pr160040.ll
new file mode 100644
index 0000000000000..865239b37112c
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/pr160040.ll
@@ -0,0 +1,24 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py UTC_ARGS: --version 6
+; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu < %s | FileCheck %s
+
+; Make sure this does not crash.
+define i32 @test(i32 %arg) {
+; CHECK-LABEL: test:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    rlwinm 4, 3, 13, 19, 19
+; CHECK-NEXT:    rlwinm 3, 3, 2, 30, 30
+; CHECK-NEXT:    xori 4, 4, 4096
+; CHECK-NEXT:    xori 3, 3, 2
+; CHECK-NEXT:    rlwimi 3, 4, 0, 31, 29
+; CHECK-NEXT:    blr
+  %icmp = icmp sgt i32 %arg, -1
+  %select = select i1 %icmp, i16 1, i16 0
+  %select1 = select i1 %icmp, i16 16384, i16 0
+  %lshr = lshr i16 %select1, 1
+  %zext = zext i16 %lshr to i32
+  %lshr2 = lshr i32 %zext, 1
+  %shl = shl i16 %select, 1
+  %zext3 = zext i16 %shl to i32
+  %or = or i32 %lshr2, %zext3
+  ret i32 %or
+}

[RolandF77]

LGTM

[github-actions]

@nikic (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.