[PATCH] D53106: [SelectionDAG] Fix behavior of glued nodes in hasPredecessorHelper.

[Nirav Dave via Phabricator via llvm-commits]

niravd created this revision.
niravd added reviewers: TimNN, bogner, jyknight.
Herald added a subscriber: dylanmckay.

Glued User nodes are implicitly predecessors of users of their glued
operand to node merging from constructing a non-immediate dependence
between glued nodes.


Repository:
  rL LLVM

https://reviews.llvm.org/D53106

Files:
  llvm/include/llvm/CodeGen/SelectionDAGNodes.h
  llvm/test/CodeGen/AVR/glue-dag-combine-bug.ll


Index: llvm/test/CodeGen/AVR/glue-dag-combine-bug.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/AVR/glue-dag-combine-bug.ll
@@ -0,0 +1,51 @@
+; RUN: llc < %s -mtriple=avr-unknown-unknown
+
+%"foo" = type { [0 x i8], i16, [0 x i8], [40 x i32], [0 x i8] }
+
+define void @bar() unnamed_addr addrspace(0) #0 personality i32 (...) addrspace(1)* @rust_eh_personality {
+start:
+  %_7.sroa.0.0..sroa_idx.i = getelementptr inbounds %"foo", %"foo"* undef, i16 0, i32 3, i16 0
+  switch i2 undef, label %bb5.i2 [
+    i2 0, label %bb2.i
+    i2 1, label %bb3.i
+    i2 -2, label %bb4.i
+  ]
+
+bb2.i:                                            ; preds = %start
+  unreachable
+
+bb3.i:                                            ; preds = %start
+  unreachable
+
+bb4.i:                                            ; preds = %start
+  br i1 undef, label %bb7, label %bb9.i5.i
+
+bb9.i5.i:                                         ; preds = %bb4.i
+  %0 = call addrspace(1) { i8, i1 } @llvm.usub.with.overflow.i8(i8 0, i8 48)
+  %1 = extractvalue { i8, i1 } %0, 0
+  %2 = zext i8 %1 to i32
+  %3 = load i32, i32* %_7.sroa.0.0..sroa_idx.i, align 1
+  %4 = call addrspace(1) { i32, i1 } @llvm.uadd.with.overflow.i32(i32 %3, i32 %2) #3
+  %5 = extractvalue { i32, i1 } %4, 0
+  store i32 %5, i32* %_7.sroa.0.0..sroa_idx.i, align 1
+  unreachable
+
+bb5.i2:                                           ; preds = %start
+  unreachable
+
+bb7:                                              ; preds = %bb4.i
+  ret void
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare { i8, i1 } @llvm.usub.with.overflow.i8(i8, i8) addrspace(1) #1
+
+declare i32 @rust_eh_personality(...) unnamed_addr addrspace(1) #2
+
+; Function Attrs: nounwind readnone speculatable
+declare { i32, i1 } @llvm.uadd.with.overflow.i32(i32, i32) addrspace(1) #1
+
+attributes #0 = { uwtable }
+attributes #1 = { nounwind readnone speculatable }
+attributes #2 = { "target-cpu"="atmega32u4" }
+attributes #3 = { nounwind }
Index: llvm/include/llvm/CodeGen/SelectionDAGNodes.h
===================================================================
--- llvm/include/llvm/CodeGen/SelectionDAGNodes.h
+++ llvm/include/llvm/CodeGen/SelectionDAGNodes.h
@@ -867,6 +867,14 @@
       }
       for (const SDValue &OpV : M->op_values()) {
         SDNode *Op = OpV.getNode();
+        // If we are adding a glued node, its glued user should be considered a
+        // predecessor as well to prevent a node merge causing a non-immediate
+        // use of a glue operand. Walk down all unvisited glue users.
+        while (auto *GN = Op->getGluedUser()) {
+          if ((GN == M) || Visited.count(GN))
+            break;
+          Op = GN;
+        }
         if (Visited.insert(Op).second)
           Worklist.push_back(Op);
         if (Op == N)


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