Reland "Fix __cfi_check not aligned to 4k on relocatable files with no executable code"

This reverts commit a093598.

Fixed test breakage.

Author: kongy

clang/lib/CodeGen/CGExpr.cpp

@@ -3431,14 +3431,12 @@ void CodeGenFunction::EmitCfiCheckStub() {
   llvm::Function *F = llvm::Function::Create(
       llvm::FunctionType::get(VoidTy, {Int64Ty, Int8PtrTy, Int8PtrTy}, false),
       llvm::GlobalValue::WeakAnyLinkage, "__cfi_check", M);
+  F->setAlignment(llvm::Align(4096));
   CGM.setDSOLocal(F);
   llvm::BasicBlock *BB = llvm::BasicBlock::Create(Ctx, "entry", F);
-  // FIXME: consider emitting an intrinsic call like
-  // call void @llvm.cfi_check(i64 %0, i8* %1, i8* %2)
-  // which can be lowered in CrossDSOCFI pass to the actual contents of
-  // __cfi_check. This would allow inlining of __cfi_check calls.
-  llvm::CallInst::Create(
-      llvm::Intrinsic::getDeclaration(M, llvm::Intrinsic::trap), "", BB);
+  // CrossDSOCFI pass is not executed if there is no executable code.
+  SmallVector<llvm::Value*> Args{F->getArg(2), F->getArg(1)};
+  llvm::CallInst::Create(M->getFunction("__cfi_check_fail"), Args, "", BB);
   llvm::ReturnInst::Create(Ctx, nullptr, BB);
 }
 
@@ -3532,9 +3530,6 @@ void CodeGenFunction::EmitCfiCheckFail() {
   }
 
   FinishFunction();
-  // The only reference to this function will be created during LTO link.
-  // Make sure it survives until then.
-  CGM.addUsedGlobal(F);
 }
 
 void CodeGenFunction::EmitUnreachable(SourceLocation Loc) {

clang/test/CodeGen/cfi-check-fail.c

@@ -72,7 +72,7 @@ void caller(void (*f)(void)) {
 // CHECK: [[CONT5]]:
 // CHECK:   ret void
 
-// CHECK: define weak void @__cfi_check(i64 %0, ptr %1, ptr %2)
+// CHECK: define weak void @__cfi_check(i64 %[[TYPE:.*]], ptr %[[ADDR:.*]], ptr %[[DATA:.*]]) align 4096
 // CHECK-NOT: }
-// CHECK: call void @llvm.trap()
+// CHECK: call void @__cfi_check_fail(ptr %[[DATA]], ptr %[[ADDR]])
 // CHECK-NEXT: ret void