[PATCH] D113897: [GVNSink] Make GVNSink resistant against self referencing instructions (PR36954)

[Dawid Jurczak via Phabricator via llvm-commits]

yurai007 updated this revision to Diff 427838.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D113897/new/

https://reviews.llvm.org/D113897

Files:
  llvm/lib/Transforms/Scalar/GVNSink.cpp
  llvm/test/Transforms/GVNSink/sink-common-code.ll


Index: llvm/test/Transforms/GVNSink/sink-common-code.ll
===================================================================
--- llvm/test/Transforms/GVNSink/sink-common-code.ll
+++ llvm/test/Transforms/GVNSink/sink-common-code.ll
@@ -759,6 +759,43 @@
   ret i32 1
 }
 
+ at 0 = global i32 0, align 4
+ at 1 = global i8 0, align 2
+
+; CHECK-LABEL: test_pr36954
+; CHECK-NOT: xor
+; PR36954 reproducer containing self referencing instruction shouldn't crash GVNSink pass.
+define void @test_pr36954() {
+bb1:
+  %i1 = load i32, i32* @0, align 4
+  %i2 = trunc i32 %i1 to i8
+  br label %bb2
+
+bb2:
+  %i3 = phi i32 [ 0, %bb1 ], [ %i10, %bb5 ]
+  %i4 = icmp eq i32 %i3, 0
+  br i1 %i4, label %bb5, label %exit
+
+bb3:
+  br i1 %i4, label %bb5, label %bb4
+
+bb4:
+  %i5 = load i8, i8* @1, align 2
+  %i6 = sub i8 %i2, %i5
+  store i8 %i6, i8* @1, align 2
+  %i7 = zext i8 %i6 to i32
+  %i8 = xor i32 %i8, %i7
+  %i9 = icmp eq i32 %i8, 0
+  br i1 %i9, label %exit, label %bb3
+
+bb5:
+  %i10 = phi i32 [ %i3, %bb2 ], [ %i8, %bb3 ]
+  br label %bb2
+
+exit:
+  ret void
+}
+
 ; CHECK: !0 = !{!1, !1, i64 0}
 ; CHECK: !1 = !{!"float", !2}
 ; CHECK: !2 = !{!"an example type tree"}
Index: llvm/lib/Transforms/Scalar/GVNSink.cpp
===================================================================
--- llvm/lib/Transforms/Scalar/GVNSink.cpp
+++ llvm/lib/Transforms/Scalar/GVNSink.cpp
@@ -381,6 +381,8 @@
   }
 };
 
+using BasicBlocksSet = SmallPtrSet<const BasicBlock *, 32>;
+
 class ValueTable {
   DenseMap<Value *, uint32_t> ValueNumbering;
   DenseMap<GVNExpression::Expression *, uint32_t> ExpressionNumbering;
@@ -388,6 +390,7 @@
   BumpPtrAllocator Allocator;
   ArrayRecycler<Value *> Recycler;
   uint32_t nextValueNumber = 1;
+  BasicBlocksSet ReachableBBs;
 
   /// Create an expression for I based on its opcode and its uses. If I
   /// touches or reads memory, the expression is also based upon its memory
@@ -419,6 +422,11 @@
 public:
   ValueTable() = default;
 
+  /// Set basic blocks reachable from entry block.
+  void setReachableBBs(const BasicBlocksSet &ReachableBBs) {
+    this->ReachableBBs = ReachableBBs;
+  }
+
   /// Returns the value number for the specified value, assigning
   /// it a new number if it did not have one before.
   uint32_t lookupOrAdd(Value *V) {
@@ -432,6 +440,9 @@
     }
 
     Instruction *I = cast<Instruction>(V);
+    if (!ReachableBBs.contains(I->getParent()))
+      return ~0U;
+
     InstructionUseExpr *exp = nullptr;
     switch (I->getOpcode()) {
     case Instruction::Load:
@@ -568,6 +579,7 @@
 
     unsigned NumSunk = 0;
     ReversePostOrderTraversal<Function*> RPOT(&F);
+    VN.setReachableBBs(BasicBlocksSet(RPOT.begin(), RPOT.end()));
     for (auto *N : RPOT)
       NumSunk += sinkBB(N);
 


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