From: Daniel Berlin <dberlin@dberlin.org>
Date: Sat, 18 Mar 2017 15:41:36 +0000 (+0000)
Subject: NewGVN: Fix PHI evaluation bug exposed by new verifier. We were checking whether... 
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=174f2f4bda045981a41e75183db17ea4e7049ae5;p=llvm

NewGVN: Fix PHI evaluation bug exposed by new verifier. We were checking whether the incoming block was reachable instead of whether the specific edge was reachable

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@298187 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Scalar/NewGVN.cpp b/lib/Transforms/Scalar/NewGVN.cpp
index a637160b8e6..0fa9b1d714a 100644
--- a/lib/Transforms/Scalar/NewGVN.cpp
+++ b/lib/Transforms/Scalar/NewGVN.cpp
@@ -444,7 +444,7 @@ PHIExpression *NewGVN::createPHIExpression(Instruction *I) {
 
   // Filter out unreachable phi operands.
   auto Filtered = make_filter_range(PN->operands(), [&](const Use &U) {
-    return ReachableBlocks.count(PN->getIncomingBlock(U));
+    return ReachableEdges.count({PN->getIncomingBlock(U), PHIBlock});
   });
 
   std::transform(Filtered.begin(), Filtered.end(), op_inserter(E),
@@ -1740,10 +1740,11 @@ void NewGVN::valueNumberMemoryPhi(MemoryPhi *MP) {
   // If all the arguments are the same, the MemoryPhi has the same value as the
   // argument.
   // Filter out unreachable blocks and self phis from our operands.
+  const BasicBlock *PHIBlock = MP->getBlock();
   auto Filtered = make_filter_range(MP->operands(), [&](const Use &U) {
     return lookupMemoryAccessEquiv(cast<MemoryAccess>(U)) != MP &&
            !isMemoryAccessTop(cast<MemoryAccess>(U)) &&
-           ReachableBlocks.count(MP->getIncomingBlock(U));
+           ReachableEdges.count({MP->getIncomingBlock(U), PHIBlock});
   });
   // If all that is left is nothing, our memoryphi is undef. We keep it as
   // InitialClass.  Note: The only case this should happen is if we have at
@@ -1822,7 +1823,7 @@ bool NewGVN::singleReachablePHIPath(const MemoryAccess *First,
   } else {
     auto *MP = cast<MemoryPhi>(First);
     auto ReachableOperandPred = [&](const Use &U) {
-      return ReachableBlocks.count(MP->getIncomingBlock(U));
+      return ReachableEdges.count({MP->getIncomingBlock(U), MP->getBlock()});
     };
     auto FilteredPhiArgs =
         make_filter_range(MP->operands(), ReachableOperandPred);
@@ -1879,7 +1880,8 @@ void NewGVN::verifyMemoryCongruency() const {
       // We can only sanely verify that MemoryDefs in the operand list all have
       // the same class.
       auto ReachableOperandPred = [&](const Use &U) {
-        return ReachableBlocks.count(FirstMP->getIncomingBlock(U)) &&
+        return ReachableEdges.count(
+                   {FirstMP->getIncomingBlock(U), FirstMP->getBlock()}) &&
                isa<MemoryDef>(U);
 
       };
diff --git a/test/Transforms/NewGVN/phi-edge-handling.ll b/test/Transforms/NewGVN/phi-edge-handling.ll
new file mode 100644
index 00000000000..6451006a694
--- /dev/null
+++ b/test/Transforms/NewGVN/phi-edge-handling.ll
@@ -0,0 +1,60 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -newgvn -S | FileCheck %s
+
+
+;; Block 6 is reachable, but edge 6->4 is not
+;; This means the phi value is undef, not 0
+; Function Attrs: ssp uwtable
+define i16 @hoge() local_unnamed_addr #0 align 2 {
+; CHECK-LABEL: @hoge(
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    switch i8 undef, label [[BB7:%.*]] [
+; CHECK-NEXT:    i8 0, label [[BB1:%.*]]
+; CHECK-NEXT:    i8 12, label [[BB2:%.*]]
+; CHECK-NEXT:    ]
+; CHECK:       bb1:
+; CHECK-NEXT:    br label [[BB6:%.*]]
+; CHECK:       bb2:
+; CHECK-NEXT:    br label [[BB4:%.*]]
+; CHECK:       bb3:
+; CHECK-NEXT:    unreachable
+; CHECK:       bb4:
+; CHECK-NEXT:    ret i16 undef
+; CHECK:       bb6:
+; CHECK-NEXT:    br i1 true, label [[BB3:%.*]], label [[BB4]], !llvm.loop !1
+; CHECK:       bb7:
+; CHECK-NEXT:    unreachable
+;
+bb:
+  switch i8 undef, label %bb7 [
+  i8 0, label %bb1
+  i8 12, label %bb2
+  ]
+
+bb1:                                              ; preds = %bb
+  br label %bb6
+
+bb2:                                              ; preds = %bb
+  br label %bb4
+
+bb3:                                              ; preds = %bb6
+  unreachable
+
+bb4:                                              ; preds = %bb6, %bb2
+  %tmp = phi i16 [ 0, %bb6 ], [ undef, %bb2 ]
+  ret i16 %tmp
+
+bb6:                                              ; preds = %bb4
+  br i1 true, label %bb3, label %bb4, !llvm.loop !1
+
+bb7:                                              ; preds = %bb
+  unreachable
+}
+
+attributes #0 = { ssp uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="penryn" "target-features"="+cx16,+fxsr,+mmx,+sse,+sse2,+sse3,+sse4.1,+ssse3,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+!llvm.ident = !{!0}
+
+!0 = !{!"clang version 5.0.0 (http://llvm.org/git/clang.git a8b933d4d1d133594fdaed35ee5814514b738f6d) (/Users/dannyb/sources/llvm-clean fc630a9b5613f544c07a8f16abcc173793df62cf)"}
+!1 = distinct !{!1, !2}
+!2 = !{!"llvm.loop.unroll.disable"}