[GlobalISel] Add a fallback path to SDISel.

When global-isel fails on a MachineFunction MF, MF will be cleaned up
and given to SDISel.
Thanks to this fallback, we can already perform correctness test even if
we support only a small portion of the functions in a test.

llvm-svn: 279891

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LLVMTargetMachine.cpp b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
index 844e1ffe681..e11eb014111 100644
--- a/llvm/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
@@ -168,6 +168,15 @@ addPassesToGenerateCode(LLVMTargetMachine *TM, PassManagerBase &PM,
     if (PassConfig->addGlobalInstructionSelect())
       return nullptr;
 
+    // Pass to reset the MachineFunction if the ISel failed.
+    PM.add(createResetMachineFunctionPass());
+
+    // Provide a fallback path when we do not want to abort on
+    // not-yet-supported input.
+    if (LLVM_UNLIKELY(!PassConfig->isGlobalISelAbortEnabled()) &&
+        PassConfig->addInstSelector())
+      return nullptr;
+
   } else if (PassConfig->addInstSelector())
     return nullptr;