Completely disable tail calls when fast-isel is enabled, as fast-isel

doesn't currently support dealing with this.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112341 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -4649,6 +4649,11 @@ void SelectionDAGBuilder::LowerCallTo(ImmutableCallSite CS, SDValue Callee,
       !isInTailCallPosition(CS, CS.getAttributes().getRetAttributes(), TLI))
     isTailCall = false;
 
+  // If there's a possibility that fast-isel has already selected some amount
+  // of the current basic block, don't emit a tail call.
+  if (isTailCall && EnableFastISel)
+    isTailCall = false;
+
   std::pair<SDValue,SDValue> Result =
     TLI.LowerCallTo(getRoot(), RetTy,
                     CS.paramHasAttr(0, Attribute::SExt),

test/CodeGen/X86/tailcall-fastisel.ll

@@ -1,8 +1,6 @@
-; RUN: llc < %s -march=x86-64 -tailcallopt -fast-isel | grep TAILCALL
+; RUN: llc < %s -march=x86-64 -tailcallopt -fast-isel | not grep TAILCALL
 
-; Fast-isel shouldn't attempt to handle this tail call, and it should
+; Fast-isel shouldn't attempt to cope with tail calls.
-; cleanly terminate instruction selection in the block after it's
-; done to avoid emitting invalid MachineInstrs.
 
 %0 = type { i64, i32, i8* }
 
@@ -11,3 +9,11 @@ fail:                                             ; preds = %entry
   %tmp20 = tail call fastcc i8* @"visit_array_aux<`Reference>"(%0 %arg, i32 undef) ; <i8*> [#uses=1]
   ret i8* %tmp20
 }
+
+define i32 @foo() nounwind {
+entry:
+ %0 = tail call i32 (...)* @bar() nounwind       ; <i32> [#uses=1]
+ ret i32 %0
+}
+
+declare i32 @bar(...) nounwind