IRGen: Call SetLLVMFunctionAttributes{,ForDefinition} on __cfi_check_fail.

[pcc]

Summary

This has the main effect of causing target-cpu and target-features to be set
on __cfi_check_fail, causing the function to become ABI-compatible with other
functions in the case where these attributes affect ABI (e.g. reserve-x18).

Technically we only need to call SetLLVMFunctionAttributes to get the target-*
attributes set, but since we're creating a definition we probably ought to
call the ForDefinition function as well.

Fixes PR44094.

[eugenis]

LGTM

clang/lib/CodeGen/CGExpr.cpp

void CodeGenFunction::EmitCfiCheckFail() {
   Args.push_back(&ArgAddr);
 
   const CGFunctionInfo &FI =
     CGM.getTypes().arrangeBuiltinFunctionDeclaration(getContext().VoidTy, Args);
 
   llvm::Function *F = llvm::Function::Create(
       llvm::FunctionType::get(VoidTy, {VoidPtrTy, VoidPtrTy}, false),
       llvm::GlobalValue::WeakODRLinkage, "__cfi_check_fail", &CGM.getModule());
+
+  CGM.SetLLVMFunctionAttributes(GlobalDecl(), FI, F);
+  CGM.SetLLVMFunctionAttributesForDefinition(nullptr, F);
   F->setVisibility(llvm::GlobalValue::HiddenVisibility);
 
   StartFunction(GlobalDecl(), CGM.getContext().VoidTy, F, FI, Args,
                 SourceLocation());
 
   // This function should not be affected by blacklist. This function does
   // not have a source location, but "src:*" would still apply. Revert any
   // changes to SanOpts made in StartFunction.

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

+// RUN: %clang_cc1 -triple aarch64-unknown-linux -fsanitize-cfi-cross-dso -target-feature +reserve-x18 -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: define weak_odr hidden void @__cfi_check_fail{{.*}} [[ATTR:#[0-9]*]]
+
+// CHECK: attributes [[ATTR]] = {{.*}} "target-features"="+reserve-x18"