Add option to disable leaf frame pointer elimination

Author: aschwaighofer

include/swift/AST/IRGenOptions.h

@@ -191,6 +191,7 @@ class IRGenOptions {
   unsigned DisableLLVMSLPVectorizer : 1;
 
   /// Disable frame pointer elimination?
+  unsigned DisableFPElimLeaf : 1;
   unsigned DisableFPElim : 1;
 
   /// Special codegen for playgrounds.
@@ -319,6 +320,7 @@ class IRGenOptions {
         DisableClangModuleSkeletonCUs(false), UseJIT(false),
         DisableLLVMOptzns(false),
         DisableSwiftSpecificLLVMOptzns(false), DisableLLVMSLPVectorizer(false),
+        DisableFPElimLeaf(false),
         DisableFPElim(true), Playground(false), EmitStackPromotionChecks(false),
         FunctionSections(false), PrintInlineTree(false), EmbedMode(IRGenEmbedMode::None),
         HasValueNamesSetting(false), ValueNames(false),

include/swift/Option/Options.td

@@ -1010,6 +1010,10 @@ def enable_private_imports : Flag<["-"], "enable-private-imports">,
   Flags<[FrontendOption, NoInteractiveOption, HelpHidden]>,
   HelpText<"Allows this module's internal and private API to be accessed">;
 
+def disable_leaf_frame_pointer_elim : Flag<["-"], "no-omit-leaf-frame-pointer">,
+  Flags<[FrontendOption, NoInteractiveOption, HelpHidden]>,
+  HelpText<"Don't omit the frame pointer for leaf functions">;
+
 def sanitize_EQ : CommaJoined<["-"], "sanitize=">,
   Flags<[FrontendOption, NoInteractiveOption]>, MetaVarName<"<check>">,
   HelpText<"Turn on runtime checks for erroneous behavior.">;

lib/Driver/ToolChains.cpp

@@ -287,6 +287,8 @@ void ToolChain::addCommonFrontendArgs(const OutputInfo &OI,
       arguments.push_back("-enable-anonymous-context-mangled-names");
   }
 
+  inputArgs.AddLastArg(arguments, options::OPT_disable_leaf_frame_pointer_elim);
+
   // Pass through any subsystem flags.
   inputArgs.AddAllArgs(arguments, options::OPT_Xllvm);
   inputArgs.AddAllArgs(arguments, options::OPT_Xcc);

lib/Frontend/CompilerInvocation.cpp

@@ -1511,6 +1511,9 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
         getRuntimeCompatVersion();
   }
 
+  if (Args.hasArg(OPT_disable_leaf_frame_pointer_elim))
+    Opts.DisableFPElimLeaf = true;
+
   return false;
 }
 

lib/IRGen/IRGenModule.cpp

@@ -988,7 +988,8 @@ bool swift::irgen::shouldRemoveTargetFeature(StringRef feature) {
 
 void IRGenModule::setHasFramePointer(llvm::AttrBuilder &Attrs,
                                      bool HasFramePointer) {
-  Attrs.addAttribute("frame-pointer", HasFramePointer ? "non-leaf" : "none");
+  auto UseFramePointer = IRGen.Opts.DisableFPElimLeaf ? "all" : "non-leaf";
+  Attrs.addAttribute("frame-pointer", HasFramePointer ? UseFramePointer : "none");
 }
 
 void IRGenModule::setHasFramePointer(llvm::Function *F,

test/IRGen/framepointer.sil

@@ -1,4 +1,5 @@
 // RUN: %target-swift-frontend -primary-file %s -emit-ir | %FileCheck %s --check-prefix=CHECK
+// RUN: %target-swift-frontend -primary-file %s -emit-ir -no-omit-leaf-frame-pointer| %FileCheck %s --check-prefix=CHECK-ALL
 // RUN: %target-swift-frontend -primary-file %s -S | %FileCheck %s  --check-prefix=CHECKASM --check-prefix=CHECKASM-%target-os-%target-cpu
 
 sil_stage canonical
@@ -30,6 +31,19 @@ entry(%i : $Int32):
 
 // CHECK: attributes [[ATTR]] = {{{.*}}"frame-pointer"="non-leaf"
 
+// CHECK-ALL: define{{.*}} swiftcc i32 @leaf_function_no_frame_pointer(i32 %0) [[ATTR:#.*]] {
+// CHECK-ALL: entry:
+// CHECK-ALL:   ret i32 %0
+// CHECK-ALL: }
+
+// CHECK-ALL: define{{.*}} swiftcc i32 @non_leaf_function_with_frame_pointer(i32 %0) [[ATTR]] {
+// CHECK-ALL: entry:
+// CHECK-ALL:   %1 = call swiftcc i32 @leaf_function_no_frame_pointer(i32 %0)
+// CHECK-ALL:   ret i32 %1
+// CHECK-ALL: }
+
+// CHECK-ALL: attributes [[ATTR]] = {{{.*}}"frame-pointer"="all"
+
 // Silence other os-archs.
 // CHECKASM: {{.*}}