commit e840e88239cf92a065cbf5f5b9c7d18bc139c0e1
author Rafael Espindola <rafael.espindola@gmail.com> Wed Oct 26 21:12:27 2011 +0000
committer Rafael Espindola <rafael.espindola@gmail.com> Wed Oct 26 21:12:27 2011 +0000
tree 35284b23a73dec41789d4f75e55078bd4a090c70
parent 75757f9fd13bffc51a6aa30eefe706c4f84d0913

This commit introduces two fake instructions MORESTACK_RET and
MORESTACK_RET_RESTORE_R10; which are lowered to a RET and a RET
followed by a MOV respectively.  Having a fake instruction prevents
the verifier from seeing a MachineBasicBlock end with a
non-terminator (MOV).  It also prevents the rather eccentric case of a
MachineBasicBlock ending with RET but having successors nevertheless.

Patch by Sanjoy Das.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143062 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/X86/X86FrameLowering.cpp

diff --git a/lib/Target/X86/X86FrameLowering.cpp b/lib/Target/X86/X86FrameLowering.cpp
index d54f4ae..ece90cb 100644
--- a/lib/Target/X86/X86FrameLowering.cpp
+++ b/lib/Target/X86/X86FrameLowering.cpp
@@ -1336,26 +1336,16 @@
 
   // The MOV R10, RAX needs to be in a different block, since the RET we emit in
   // allocMBB needs to be last (terminating) instruction.
-  MachineBasicBlock *restoreR10MBB = NULL;
-  if (IsNested)
-    restoreR10MBB = MF.CreateMachineBasicBlock();
 
   for (MachineBasicBlock::livein_iterator i = prologueMBB.livein_begin(),
          e = prologueMBB.livein_end(); i != e; i++) {
     allocMBB->addLiveIn(*i);
     checkMBB->addLiveIn(*i);
-
-    if (IsNested)
-      restoreR10MBB->addLiveIn(*i);
-  }
-
-  if (IsNested) {
-    allocMBB->addLiveIn(X86::R10);
-    restoreR10MBB->addLiveIn(X86::RAX);
   }
 
   if (IsNested)
-    MF.push_front(restoreR10MBB);
+    allocMBB->addLiveIn(X86::R10);
+
   MF.push_front(allocMBB);
   MF.push_front(checkMBB);
 
@@ -1425,18 +1415,12 @@
   if (!Is64Bit)
     BuildMI(allocMBB, DL, TII.get(X86::ADD32ri), X86::ESP).addReg(X86::ESP)
       .addImm(8);
-  BuildMI(allocMBB, DL, TII.get(X86::RET));
-
   if (IsNested)
-    BuildMI(restoreR10MBB, DL, TII.get(X86::MOV64rr), X86::R10)
-      .addReg(X86::RAX);
+    BuildMI(allocMBB, DL, TII.get(X86::MORESTACK_RET_RESTORE_R10));
+  else
+    BuildMI(allocMBB, DL, TII.get(X86::MORESTACK_RET));
 
-  if (IsNested) {
-    allocMBB->addSuccessor(restoreR10MBB);
-    restoreR10MBB->addSuccessor(&prologueMBB);
-  } else {
-    allocMBB->addSuccessor(&prologueMBB);
-  }
+  allocMBB->addSuccessor(&prologueMBB);
 
   checkMBB->addSuccessor(allocMBB);
   checkMBB->addSuccessor(&prologueMBB);