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
diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 3941995..9a0d521 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -935,6 +935,7 @@
STI.isTarget64BitILP32()
? getX86SubSuperRegister(FramePtr, 64) : FramePtr;
unsigned BasePtr = TRI->getBaseRegister();
+ bool HasWinCFI = false;
// Debug location must be unknown since the first debug location is used
// to determine the end of the prologue.
@@ -1063,6 +1064,7 @@
}
if (NeedsWinCFI) {
+ HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_PushReg))
.addImm(FramePtr)
.setMIFlag(MachineInstr::FrameSetup);
@@ -1124,6 +1126,7 @@
}
if (NeedsWinCFI) {
+ HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_PushReg)).addImm(Reg).setMIFlag(
MachineInstr::FrameSetup);
}
@@ -1209,10 +1212,12 @@
emitSPUpdate(MBB, MBBI, -(int64_t)NumBytes, /*InEpilogue=*/false);
}
- if (NeedsWinCFI && NumBytes)
+ if (NeedsWinCFI && NumBytes) {
+ HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_StackAlloc))
.addImm(NumBytes)
.setMIFlag(MachineInstr::FrameSetup);
+ }
int SEHFrameOffset = 0;
unsigned SPOrEstablisher;
@@ -1259,6 +1264,7 @@
// If this is not a funclet, emit the CFI describing our frame pointer.
if (NeedsWinCFI && !IsFunclet) {
+ HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_SetFrame))
.addImm(FramePtr)
.addImm(SEHFrameOffset)
@@ -1295,6 +1301,7 @@
int Offset = getFrameIndexReference(MF, FI, IgnoredFrameReg);
Offset += SEHFrameOffset;
+ HasWinCFI = true;
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_SaveXMM))
.addImm(Reg)
.addImm(Offset)
@@ -1304,7 +1311,7 @@
}
}
- if (NeedsWinCFI)
+ if (NeedsWinCFI && HasWinCFI)
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_EndPrologue))
.setMIFlag(MachineInstr::FrameSetup);
@@ -1396,6 +1403,9 @@
if (Fn->getCallingConv() == CallingConv::X86_INTR)
BuildMI(MBB, MBBI, DL, TII.get(X86::CLD))
.setMIFlag(MachineInstr::FrameSetup);
+
+ // At this point we know if the function has WinCFI or not.
+ MF.setHasWinCFI(HasWinCFI);
}
bool X86FrameLowering::canUseLEAForSPInEpilogue(
@@ -1630,7 +1640,7 @@
// into the epilogue. To cope with that, we insert an epilogue marker here,
// then replace it with a 'nop' if it ends up immediately after a CALL in the
// final emitted code.
- if (NeedsWinCFI)
+ if (NeedsWinCFI && MF.hasWinCFI())
BuildMI(MBB, MBBI, DL, TII.get(X86::SEH_Epilogue));
if (!RetOpcode || !isTailCallOpcode(*RetOpcode)) {
diff --git a/llvm/lib/Target/X86/X86MCInstLower.cpp b/llvm/lib/Target/X86/X86MCInstLower.cpp
index 7dfe9f2..8f46168 100644
--- a/llvm/lib/Target/X86/X86MCInstLower.cpp
+++ b/llvm/lib/Target/X86/X86MCInstLower.cpp
@@ -1420,37 +1420,45 @@
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);