Disable check noreturn call in stack protector

[xiangzhangllvm]

Summary

Background
We enhance the stack protector at D139254
From then, tack protector will check the stack before return and call no-return function.
(Before, we only check before return, this give attack space in our user's code, and uses
hope we can fix it.)
In D139254 smeenai hope to use a option come back
to the previous action (only check for return) by consider the code size in their project. So I
implemented this patch.
To encourage users to use strict stack protect (both check for return and no-return call), I only
implement the option as a LLVM option first. If we have more requirements as smeenai do. We
will consider add a standard FE option.

[lanza]

I work with Shoaib and this looks like a good solution for us! Thank you!

llvm/lib/CodeGen/StackProtector.cpp

 #define DEBUG_TYPE "stack-protector"
 
 STATISTIC(NumFunProtected, "Number of functions protected");
 STATISTIC(NumAddrTaken, "Number of local variables that have their address"
                         " taken.");
 
 static cl::opt<bool> EnableSelectionDAGSP("enable-selectiondag-sp",
                                           cl::init(true), cl::Hidden);
+static cl::opt<bool> DisableCheckNoReturn("disable-check-noreturn-call",
+                                          cl::init(false), cl::Hidden);
 
 char StackProtector::ID = 0;
 
 StackProtector::StackProtector() : FunctionPass(ID) {
   initializeStackProtectorPass(*PassRegistry::getPassRegistry());
 }
 
 INITIALIZE_PASS_BEGIN(StackProtector, DEBUG_TYPE,
bool StackProtector::InsertStackProtectors() {
   AllocaInst *AI = nullptr; // Place on stack that stores the stack guard.
   BasicBlock *FailBB = nullptr;
 
   for (BasicBlock &BB : llvm::make_early_inc_range(*F)) {
     // This is stack protector auto generated check BB, skip it.
     if (&BB == FailBB)
       continue;
     Instruction *CheckLoc = dyn_cast<ReturnInst>(BB.getTerminator());
-    if (!CheckLoc) {
+    if (!CheckLoc && !DisableCheckNoReturn) {
       for (auto &Inst : BB) {
         auto *CB = dyn_cast<CallBase>(&Inst);
         if (!CB)
           continue;
         if (!CB->doesNotReturn())
           continue;
         // Do stack check before non-return calls (e.g: __cxa_throw)
         CheckLoc = CB;

llvm/test/CodeGen/X86/stack-protector-no-return.ll

 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc %s -mtriple=x86_64-unknown-linux-gnu -o - -verify-dom-info | FileCheck %s
+; RUN: llc %s -mtriple=x86_64-unknown-linux-gnu -disable-check-noreturn-call=true -o - -verify-dom-info | FileCheck --check-prefix=DISNOTET %s
 
 ; Function Attrs: sspreq
 define void @_Z7catchesv() #0 personality i8* null {
 ; CHECK-LABEL: _Z7catchesv:
 ; CHECK:       # %bb.0: # %entry
 ; CHECK-NEXT:    pushq %rax
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
 ; CHECK-NEXT:    movq %fs:40, %rax

 ; CHECK-NEXT:    jne .LBB0_6
 ; CHECK-NEXT:  # %bb.5: # %SP_return3
 ; CHECK-NEXT:    popq %rax
 ; CHECK-NEXT:    .cfi_def_cfa_offset 8
 ; CHECK-NEXT:    retq
 ; CHECK-NEXT:  .LBB0_6: # %CallStackCheckFailBlk
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
 ; CHECK-NEXT:    callq __stack_chk_fail@PLT
+;
+; DISNOTET-LABEL: _Z7catchesv:
+; DISNOTET:       # %bb.0: # %entry
+; DISNOTET-NEXT:    pushq %rax
+; DISNOTET-NEXT:    .cfi_def_cfa_offset 16
+; DISNOTET-NEXT:    movq %fs:40, %rax
+; DISNOTET-NEXT:    movq %rax, (%rsp)
+; DISNOTET-NEXT:  .Ltmp0:
+; DISNOTET-NEXT:    xorl %eax, %eax
+; DISNOTET-NEXT:    xorl %edi, %edi
+; DISNOTET-NEXT:    xorl %esi, %esi
+; DISNOTET-NEXT:    xorl %edx, %edx
+; DISNOTET-NEXT:    callq *%rax
+; DISNOTET-NEXT:  .Ltmp1:
+; DISNOTET-NEXT:  # %bb.1: # %invoke.cont
+; DISNOTET-NEXT:  .Ltmp2:
+; DISNOTET-NEXT:    xorl %eax, %eax
+; DISNOTET-NEXT:    xorl %edi, %edi
+; DISNOTET-NEXT:    callq *%rax
+; DISNOTET-NEXT:  .Ltmp3:
+; DISNOTET-NEXT:  # %bb.2: # %invoke.cont2
+; DISNOTET-NEXT:  .LBB0_3: # %lpad1
+; DISNOTET-NEXT:  .Ltmp4:
+; DISNOTET-NEXT:    movq %fs:40, %rax
+; DISNOTET-NEXT:    cmpq (%rsp), %rax
+; DISNOTET-NEXT:    jne .LBB0_5
+; DISNOTET-NEXT:  # %bb.4: # %SP_return
+; DISNOTET-NEXT:    popq %rax
+; DISNOTET-NEXT:    .cfi_def_cfa_offset 8
+; DISNOTET-NEXT:    retq
+; DISNOTET-NEXT:  .LBB0_5: # %CallStackCheckFailBlk
+; DISNOTET-NEXT:    .cfi_def_cfa_offset 16
+; DISNOTET-NEXT:    callq __stack_chk_fail@PLT
 entry:
   %call = invoke i64 null(i32 0, i8* null, i64 0)
           to label %invoke.cont unwind label %lpad1
 
 invoke.cont:                                      ; preds = %entry
   invoke void null(i32 0) #1
           to label %invoke.cont2 unwind label %lpad1