If we have a VLA that has a "use" in a metadata node that's then used

here but it has no other uses, then we have a problem. E.g.,

  int foo (const int *x) {
    char a[*x];
    return 0;
  }

If we assign 'a' a vreg and fast isel later on has to use the selection
DAG isel, it will want to copy the value to the vreg. However, there are
no uses, which goes counter to what selection DAG isel expects.
<rdar://problem/11134152>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153705 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 4db10b7586..5de66670b2 100644
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -599,7 +599,18 @@ bool FastISel::SelectCall(const User *I) {
     if (!Reg)
       Reg = lookUpRegForValue(Address);
 
-    if (!Reg && isa<Instruction>(Address) &&
+    // If we have a VLA that has a "use" in a metadata node that's then used
+    // here but it has no other uses, then we have a problem. E.g.,
+    //
+    //   int foo (const int *x) {
+    //     char a[*x];
+    //     return 0;
+    //   }
+    //
+    // If we assign 'a' a vreg and fast isel later on has to use the selection
+    // DAG isel, it will want to copy the value to the vreg. However, there are
+    // no uses, which goes counter to what selection DAG isel expects.
+    if (!Reg && !Address->use_empty() && isa<Instruction>(Address) &&
         (!isa<AllocaInst>(Address) ||
          !FuncInfo.StaticAllocaMap.count(cast<AllocaInst>(Address))))
       Reg = FuncInfo.InitializeRegForValue(Address);