[AArch64][GlobalISel] Always fall back on tail calls with -tailcallopt

-tailcallopt requires that we perform different stack adjustments than with
sibling calls. For example, the `@caller_to0_from8` function in
test/CodeGen/AArch64/tail-call.ll requires that we adjust SP. Without
-tailcallopt, this adjustment does not happen. With it, however, it is expected.

So, to ensure that adding sibling call support doesn't break -tailcallopt,
make CallLowering always fall back on possible tail calls when -tailcallopt
is passed in.

Update test/CodeGen/AArch64/tail-call.ll with a GlobalISel line to make sure
that we don't differ from the SDAG implementation at any point.

Differential Revision: https://reviews.llvm.org/D67245

llvm-svn: 371227

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64CallLowering.cpp b/llvm/lib/Target/AArch64/AArch64CallLowering.cpp
index e97b329985a..ffca0e76b6d 100644
--- a/llvm/lib/Target/AArch64/AArch64CallLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64CallLowering.cpp
@@ -567,6 +567,12 @@ bool AArch64CallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
     return false;
   }
 
+  if (Info.IsTailCall && MF.getTarget().Options.GuaranteedTailCallOpt) {
+    // TODO: Until we lower all tail calls, we should fall back on this.
+    LLVM_DEBUG(dbgs() << "Cannot handle -tailcallopt yet.\n");
+    return false;
+  }
+
   SmallVector<ArgInfo, 8> SplitArgs;
   for (auto &OrigArg : Info.OrigArgs) {
     splitToValueTypes(OrigArg, SplitArgs, DL, MRI, Info.CallConv);