ARM: correctly determine final tBX_LR in Thumb1 functions

The changes caused by folding an sp-adjustment into a "pop" previously
disrupted the forward search for the final real instruction in a
terminating block. This switches to a backward search (skipping debug
instrs).

This fixes PR18399.

Patch by Zhaoshi.

llvm-svn: 199266

1 files changed, 3 insertions, 3 deletions

diff --git a/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp b/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
index d8546da..2a587dd 100644
--- a/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
+++ b/llvm/lib/Target/ARM/Thumb1FrameLowering.cpp
@@ -304,9 +304,9 @@ void Thumb1FrameLowering::emitEpilogue(MachineFunction &MF,
     // we need to update the SP after popping the value. Therefore, we
     // pop the old LR into R3 as a temporary.
 
-    // Move back past the callee-saved register restoration
-    while (MBBI != MBB.end() && isCSRestore(MBBI, CSRegs))
-      ++MBBI;
+    // Get the last instruction, tBX_RET
+    MBBI = MBB.getLastNonDebugInstr();
+    assert (MBBI->getOpcode() == ARM::tBX_RET);
     // Epilogue for vararg functions: pop LR to R3 and branch off it.
     AddDefaultPred(BuildMI(MBB, MBBI, dl, TII.get(ARM::tPOP)))
       .addReg(ARM::R3, RegState::Define);