Consider this function:
void foo() { __builtin_unreachable(); }
It will output the following on Darwin X86:
_func1:
Leh_func_begin0:
pushq %rbp
Ltmp0:
movq %rsp, %rbp
Ltmp1:
Leh_func_end0:
This prolog adds a new Call Frame Information (CFI) row to the FDE with an
address that is not within the address range of the code it describes -- part is
equal to the end of the function -- and therefore results in an invalid EH
frame. If we emit a nop in this situation, then the CFI row is now within the
address range.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108568 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 3d6dbb7..942b53a 100644
--- a/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -599,12 +599,15 @@
// Print out code for the function.
bool HasAnyRealCode = false;
+ const MachineInstr *LastMI = 0;
for (MachineFunction::const_iterator I = MF->begin(), E = MF->end();
I != E; ++I) {
// Print a label for the basic block.
EmitBasicBlockStart(I);
for (MachineBasicBlock::const_iterator II = I->begin(), IE = I->end();
II != IE; ++II) {
+ LastMI = II;
+
// Print the assembly for the instruction.
if (!II->isLabel() && !II->isImplicitDef() && !II->isKill() &&
!II->isDebugValue()) {
@@ -652,11 +655,18 @@
}
}
}
-
+
+ // If the last instruction was a prolog label, then we have a situation where
+ // we emitted a prolog but no function body. This results in the ending prolog
+ // label equaling the end of function label and an invalid "row" in the
+ // FDE. We need to emit a noop in this situation so that the FDE's rows are
+ // valid.
+ bool RequiresNoop = LastMI && LastMI->getOpcode()==TargetOpcode::PROLOG_LABEL;
+
// If the function is empty and the object file uses .subsections_via_symbols,
// then we need to emit *something* to the function body to prevent the
// labels from collapsing together. Just emit a noop.
- if (MAI->hasSubsectionsViaSymbols() && !HasAnyRealCode) {
+ if ((MAI->hasSubsectionsViaSymbols() && !HasAnyRealCode) || RequiresNoop) {
MCInst Noop;
TM.getInstrInfo()->getNoopForMachoTarget(Noop);
if (Noop.getOpcode()) {