[NewGVN] Update additionalUsers when we simplify to a value.

Otherwise we don't revisit an instruction that could be simplified,
and when we verify, we discover there's something that changed, i.e.
what we had wasn't a maximal fixpoint.

Fixes PR32836.

llvm-svn: 303715

2 files changed, 49 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
index 5cfbf6baeaa..3245940a0dd 100644
--- a/llvm/lib/Transforms/Scalar/NewGVN.cpp
+++ b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -955,6 +955,10 @@ const Expression *NewGVN::checkSimplificationResults(Expression *E,
 
   CongruenceClass *CC = ValueToClass.lookup(V);
   if (CC && CC->getDefiningExpr()) {
+    // If we simplified to something else, we need to communicate
+    // that we're users of the value we simplified to.
+    if (I != V)
+      addAdditionalUsers(V, I);
     if (I)
       DEBUG(dbgs() << "Simplified " << *I << " to "
                    << " expression " << *CC->getDefiningExpr() << "\n");
diff --git a/llvm/test/Transforms/NewGVN/pr32836.ll b/llvm/test/Transforms/NewGVN/pr32836.ll
new file mode 100644
index 00000000000..623f216101b
--- /dev/null
+++ b/llvm/test/Transforms/NewGVN/pr32836.ll
@@ -0,0 +1,45 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -newgvn %s | FileCheck %s
+
+%struct.anon = type { i32 }
+@b = external global %struct.anon
+define void @tinkywinky(i1 %patatino) {
+; CHECK-LABEL: @tinkywinky(
+; CHECK-NEXT:    store i32 8, i32* null
+; CHECK-NEXT:    br i1 [[PATATINO:%.*]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
+; CHECK:       if.then:
+; CHECK-NEXT:    br label [[L:%.*]]
+; CHECK:       L:
+; CHECK-NEXT:    br label [[IF_END]]
+; CHECK:       if.end:
+; CHECK-NEXT:    [[TMP1:%.*]] = load i32, i32* null
+; CHECK-NEXT:    [[BF_LOAD1:%.*]] = load i32, i32* getelementptr inbounds (%struct.anon, %struct.anon* @b, i64 0, i32 0)
+; CHECK-NEXT:    [[BF_VALUE:%.*]] = and i32 [[TMP1]], 536870911
+; CHECK-NEXT:    [[BF_CLEAR:%.*]] = and i32 [[BF_LOAD1]], -536870912
+; CHECK-NEXT:    [[BF_SET:%.*]] = or i32 [[BF_CLEAR]], [[BF_VALUE]]
+; CHECK-NEXT:    store i32 [[BF_SET]], i32* getelementptr inbounds (%struct.anon, %struct.anon* @b, i64 0, i32 0)
+; CHECK-NEXT:    br label [[LOR_END:%.*]]
+; CHECK:       lor.end:
+; CHECK-NEXT:    br label [[L]]
+;
+  store i32 8, i32* null
+  br i1 %patatino, label %if.end, label %if.then
+if.then:
+  store i32 8, i32* null
+  br label %L
+L:
+  br label %if.end
+if.end:
+  %tmp1 = load i32, i32* null
+  %bf.load1 = load i32, i32* getelementptr (%struct.anon, %struct.anon* @b, i64 0, i32 0)
+  %bf.value = and i32 %tmp1, 536870911
+  %bf.clear = and i32 %bf.load1, -536870912
+  %bf.set = or i32 %bf.clear, %bf.value
+  store i32 %bf.set, i32* getelementptr (%struct.anon, %struct.anon* @b, i64 0, i32 0)
+  br label %lor.end
+lor.end:
+  %bf.load4 = load i32, i32* getelementptr (%struct.anon, %struct.anon* @b, i64 0, i32 0)
+  %tmp4 = and i32 %bf.load4, 536870911
+  %or = or i32 0, %tmp4
+  br label %L
+}