From b4afb137efbc38462707bab9f5e8bc5c2d07cd2d Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Fri, 20 Nov 2009 02:51:26 +0000
Subject: [PATCH] Fix fast-isel to avoid selecting the return instruction if a
 tail call has been encountered.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@89444 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/llvm/CodeGen/SelectionDAGISel.h       |  3 ++-
 lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp | 18 +++++++++++++++---
 test/CodeGen/X86/tailcall-fastisel.ll         | 13 +++++++++++++
 3 files changed, 30 insertions(+), 4 deletions(-)
 create mode 100644 test/CodeGen/X86/tailcall-fastisel.ll

diff --git a/include/llvm/CodeGen/SelectionDAGISel.h b/include/llvm/CodeGen/SelectionDAGISel.h
index 5d33224cbe2..adf89b0ce03 100644
--- a/include/llvm/CodeGen/SelectionDAGISel.h
+++ b/include/llvm/CodeGen/SelectionDAGISel.h
@@ -127,7 +127,8 @@ private:
 
   void SelectBasicBlock(BasicBlock *LLVMBB,
                         BasicBlock::iterator Begin,
-                        BasicBlock::iterator End);
+                        BasicBlock::iterator End,
+                        bool &HadTailCall);
   void CodeGenAndEmitDAG();
   void LowerArguments(BasicBlock *BB);
   
diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index ab5f21e4337..3a54a9ccd91 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -376,7 +376,8 @@ static void copyCatchInfo(BasicBlock *SrcBB, BasicBlock *DestBB,
 
 void SelectionDAGISel::SelectBasicBlock(BasicBlock *LLVMBB,
                                         BasicBlock::iterator Begin,
-                                        BasicBlock::iterator End) {
+                                        BasicBlock::iterator End,
+                                        bool &HadTailCall) {
   SDL->setCurrentBasicBlock(BB);
   MetadataContext &TheMetadata = LLVMBB->getParent()->getContext().getMetadata();
   unsigned MDDbgKind = TheMetadata.getMDKind("dbg");
@@ -421,6 +422,7 @@ void SelectionDAGISel::SelectBasicBlock(BasicBlock *LLVMBB,
 
   // Final step, emit the lowered DAG as machine code.
   CodeGenAndEmitDAG();
+  HadTailCall = SDL->HasTailCall;
   SDL->clear();
 }
 
@@ -797,7 +799,16 @@ void SelectionDAGISel::SelectAllBasicBlocks(Function &Fn,
           }
 
           SDL->setCurDebugLoc(FastIS->getCurDebugLoc());
-          SelectBasicBlock(LLVMBB, BI, next(BI));
+
+          bool HadTailCall = false;
+          SelectBasicBlock(LLVMBB, BI, next(BI), HadTailCall);
+
+          // If the call was emitted as a tail call, we're done with the block.
+          if (HadTailCall) {
+            BI = End;
+            break;
+          }
+
           // If the instruction was codegen'd with multiple blocks,
           // inform the FastISel object where to resume inserting.
           FastIS->setCurrentBlock(BB);
@@ -827,7 +838,8 @@ void SelectionDAGISel::SelectAllBasicBlocks(Function &Fn,
       // If FastISel is run and it has known DebugLoc then use it.
       if (FastIS && !FastIS->getCurDebugLoc().isUnknown())
         SDL->setCurDebugLoc(FastIS->getCurDebugLoc());
-      SelectBasicBlock(LLVMBB, BI, End);
+      bool HadTailCall;
+      SelectBasicBlock(LLVMBB, BI, End, HadTailCall);
     }
 
     FinishBasicBlock();
diff --git a/test/CodeGen/X86/tailcall-fastisel.ll b/test/CodeGen/X86/tailcall-fastisel.ll
new file mode 100644
index 00000000000..d54fb4115b0
--- /dev/null
+++ b/test/CodeGen/X86/tailcall-fastisel.ll
@@ -0,0 +1,13 @@
+; RUN: llc < %s -march=x86-64 -tailcallopt -fast-isel | grep TAILCALL
+
+; Fast-isel shouldn't attempt to handle this tail call, and it should
+; cleanly terminate instruction selection in the block after it's
+; done to avoid emitting invalid MachineInstrs.
+
+%0 = type { i64, i32, i8* }
+
+define fastcc i8* @"visit_array_aux<`Reference>"(%0 %arg, i32 %arg1) nounwind {
+fail:                                             ; preds = %entry
+  %tmp20 = tail call fastcc i8* @"visit_array_aux<`Reference>"(%0 %arg, i32 undef) ; <i8*> [#uses=1]
+  ret i8* %tmp20
+}
-- 
2.34.1