[Inlining] Add a clang option to limit inlining of functions

Add the clang option -finline-max-stacksize=<N> to suppress inlining
of functions whose stack size exceeds the given value.

Reviewed By: aeubanks

Differential Revision: https://reviews.llvm.org/D131986

clang/docs/ClangCommandLineReference.rst

@@ -945,6 +945,10 @@ Inline suitable functions
 
 Inline functions which are (explicitly or implicitly) marked inline
 
+.. option:: -finline-max-stacksize=<arg>
+
+Suppress inlining of functions with a stacksize larger than <arg> bytes.
+
 .. option:: -fno-legacy-pass-manager, -fexperimental-new-pass-manager
 
 .. option:: -fno-sanitize-ignorelist, -fno-sanitize-blacklist

clang/include/clang/Basic/CodeGenOptions.def

@@ -399,6 +399,9 @@ CODEGENOPT(CodeViewGHash, 1, 0)
 /// The kind of inlining to perform.
 ENUM_CODEGENOPT(Inlining, InliningMethod, 2, NormalInlining)
 
+/// The maximum stack size a function can have to be considered for inlining.
+VALUE_CODEGENOPT(InlineMaxStackSize, 32, UINT_MAX)
+
 // Vector functions library to use.
 ENUM_CODEGENOPT(VecLib, VectorLibrary, 3, NoLibrary)
 

clang/include/clang/Driver/Options.td

@@ -1985,6 +1985,11 @@ def finline_functions : Flag<["-"], "finline-functions">, Group<f_clang_Group>,
 def finline_hint_functions: Flag<["-"], "finline-hint-functions">, Group<f_clang_Group>, Flags<[CC1Option]>,
   HelpText<"Inline functions which are (explicitly or implicitly) marked inline">;
 def finline : Flag<["-"], "finline">, Group<clang_ignored_f_Group>;
+def finline_max_stacksize_EQ
+    : Joined<["-"], "finline-max-stacksize=">,
+      Group<f_Group>, Flags<[CoreOption, CC1Option]>,
+      HelpText<"Suppress inlining of functions whose stack size exceeds the given value">,
+      MarshallingInfoInt<CodeGenOpts<"InlineMaxStackSize">, "UINT_MAX">;
 defm jmc : BoolFOption<"jmc",
   CodeGenOpts<"JMCInstrument">, DefaultFalse,
   PosFlag<SetTrue, [CC1Option], "Enable just-my-code debugging">,

clang/lib/CodeGen/CodeGenModule.cpp

@@ -2372,6 +2372,9 @@ void CodeGenModule::SetFunctionAttributes(GlobalDecl GD, llvm::Function *F,
   if (getLangOpts().OpenMP && FD->hasAttr<OMPDeclareSimdDeclAttr>())
     getOpenMPRuntime().emitDeclareSimdFunction(FD, F);
 
+  if (CodeGenOpts.InlineMaxStackSize != UINT_MAX)
+    F->addFnAttr("inline-max-stacksize", llvm::utostr(CodeGenOpts.InlineMaxStackSize));
+
   if (const auto *CB = FD->getAttr<CallbackAttr>()) {
     // Annotate the callback behavior as metadata:
     //  - The callback callee (as argument number).

clang/lib/Driver/ToolChains/Clang.cpp

@@ -6592,6 +6592,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
     InlineArg->render(Args, CmdArgs);
   }
 
+  Args.AddLastArg(CmdArgs, options::OPT_finline_max_stacksize_EQ);
+
   // FIXME: Find a better way to determine whether the language has modules
   // support by default, or just assume that all languages do.
   bool HaveModules =

clang/test/CodeGen/inline-stacksize.c

@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -O2 -emit-llvm %s -o - | FileCheck %s --check-prefixes NOOPT
+// RUN: %clang_cc1 -O2 -finline-max-stacksize=64 -emit-llvm %s -o - | FileCheck %s --check-prefix OPT
+
+void foo() {}
+
+// NOOPT-NOT: inline-max-stacksize
+// OPT:       define {{.*}}@foo{{.*}}#[[ATTR:[0-9]+]]
+// OPT:       attributes #[[ATTR]] = {{.*}}"inline-max-stacksize"="64"