Win64: Don't emit unwind info for "leaf" functions (PR30337)

According to MSDN (see the PR), functions which don't touch any callee-saved
registers (including %rsp) don't need any unwind info.

This patch makes LLVM not emit unwind info for such functions, to save
binary size.

Differential Revision: https://reviews.llvm.org/D24748

llvm-svn: 282185

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 7dfe9f2829a..8f4616851cd 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1420,37 +1420,45 @@ void X86AsmPrinter::EmitInstruction(const MachineInstr *MI) {
     return;
 
   case X86::SEH_PushReg:
+    assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
     OutStreamer->EmitWinCFIPushReg(RI->getSEHRegNum(MI->getOperand(0).getImm()));
     return;
 
   case X86::SEH_SaveReg:
+    assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
     OutStreamer->EmitWinCFISaveReg(RI->getSEHRegNum(MI->getOperand(0).getImm()),
                                    MI->getOperand(1).getImm());
     return;
 
   case X86::SEH_SaveXMM:
+    assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
     OutStreamer->EmitWinCFISaveXMM(RI->getSEHRegNum(MI->getOperand(0).getImm()),
                                    MI->getOperand(1).getImm());
     return;
 
   case X86::SEH_StackAlloc:
+    assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
     OutStreamer->EmitWinCFIAllocStack(MI->getOperand(0).getImm());
     return;
 
   case X86::SEH_SetFrame:
+    assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
     OutStreamer->EmitWinCFISetFrame(RI->getSEHRegNum(MI->getOperand(0).getImm()),
                                     MI->getOperand(1).getImm());
     return;
 
   case X86::SEH_PushFrame:
+    assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
     OutStreamer->EmitWinCFIPushFrame(MI->getOperand(0).getImm());
     return;
 
   case X86::SEH_EndPrologue:
+    assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
     OutStreamer->EmitWinCFIEndProlog();
     return;
 
   case X86::SEH_Epilogue: {
+    assert(MF->hasWinCFI() && "SEH_ instruction in function without WinCFI?");
     MachineBasicBlock::const_iterator MBBI(MI);
     // Check if preceded by a call and emit nop if so.
     for (MBBI = PrevCrossBBInst(MBBI);