[PATCH] D71441: [Clang FE, SystemZ] Recognize -mpacked-stack CL option

[Jonas Paulsson via Phabricator via llvm-commits]

jonpa created this revision.
jonpa added reviewers: uweigand, bkramer.

Recognize -mpacked-stack from the command line and add a function attribute "mpacked-stack"="true" when passed.

I compared building benchmarks with -mpacked-stack vs master with this change in SystemZFrameLowering.cpp:

  static bool usePackedStack(MachineFunction &MF) {
   -  bool HasPackedStackAttr = MF.getFunction().hasFnAttribute("packed-stack");
   +  bool HasPackedStackAttr = true; //MF.getFunction().hasFnAttribute("packed-stack");
      bool IsVarArg = MF.getFunction().isVarArg();

I found that all files look the same, except for all those who contain the __clang_call_terminate function, which gets the default stack layout even when -mpacked-stack is passed. This seems to relate to exceptions, and my guess is this doesn't need to be handled, but it probably could get the "packed-stack" attribute added somewhere in clang/lib/CodeGen if needed...

Would we need to check in the backend that we don't have the attribute "packed-stack"="false", in case somebody would edit that by hand?


https://reviews.llvm.org/D71441

Files:
  clang/include/clang/Basic/CodeGenOptions.def
  clang/include/clang/Driver/Options.td
  clang/lib/CodeGen/CodeGenFunction.cpp
  clang/lib/Driver/ToolChains/Clang.cpp
  clang/lib/Frontend/CompilerInvocation.cpp
  clang/test/CodeGen/packed-stack.c


Index: clang/test/CodeGen/packed-stack.c
===================================================================
--- /dev/null
+++ clang/test/CodeGen/packed-stack.c
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -mpacked-stack -triple s390x-ibm-linux -emit-llvm \
+// RUN:   -o - %s 2>&1 | FileCheck  %s
+// RUN: not %clang_cc1 -mpacked-stack -triple x86_64-linux-gnu \
+// RUN:   -emit-llvm -o - %s 2>&1 | FileCheck -check-prefix=X86 %s
+
+int foo(void) {
+  return 0;
+}
+
+//CHECK: attributes #0 = { {{.*}}"packed-stack"="true"{{.*}} }
+//X86: error: option '-mpacked-stack' cannot be specified on this target
Index: clang/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- clang/lib/Frontend/CompilerInvocation.cpp
+++ clang/lib/Frontend/CompilerInvocation.cpp
@@ -1104,6 +1104,7 @@
   Opts.InstrumentForProfiling = Args.hasArg(OPT_pg);
   Opts.CallFEntry = Args.hasArg(OPT_mfentry);
   Opts.MNopMCount = Args.hasArg(OPT_mnop_mcount);
+  Opts.PackedStack = Args.hasArg(OPT_mpacked_stack);
   Opts.EmitOpenCLArgMetadata = Args.hasArg(OPT_cl_kernel_arg_info);
 
   if (const Arg *A = Args.getLastArg(OPT_fcf_protection_EQ)) {
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -5014,6 +5014,8 @@
   if (TC.SupportsProfiling())
     Args.AddLastArg(CmdArgs, options::OPT_mnop_mcount);
 
+  Args.AddLastArg(CmdArgs, options::OPT_mpacked_stack);
+
   if (Args.getLastArg(options::OPT_fapple_kext) ||
       (Args.hasArg(options::OPT_mkernel) && types::isCXX(InputType)))
     CmdArgs.push_back("-fapple-kext");
Index: clang/lib/CodeGen/CodeGenFunction.cpp
===================================================================
--- clang/lib/CodeGen/CodeGenFunction.cpp
+++ clang/lib/CodeGen/CodeGenFunction.cpp
@@ -971,6 +971,14 @@
     }
   }
 
+  if (CGM.getCodeGenOpts().PackedStack) {
+    if (getContext().getTargetInfo().getTriple().getArch() !=
+        llvm::Triple::systemz)
+      CGM.getDiags().Report(diag::err_opt_not_valid_on_target)
+        << "-mpacked-stack";
+    Fn->addFnAttr("packed-stack", "true");
+  }
+
   if (RetTy->isVoidType()) {
     // Void type; nothing to return.
     ReturnValue = Address::invalid();
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -2474,6 +2474,8 @@
   Flags<[CC1Option]>, Group<m_Group>;
 def mnop_mcount : Flag<["-"], "mnop-mcount">, HelpText<"Generate mcount/__fentry__ calls as nops. To activate they need to be patched in.">,
   Flags<[CC1Option]>, Group<m_Group>;
+def mpacked_stack : Flag<["-"], "mpacked-stack">, HelpText<"Use packed stack layout (SystemZ only).">,
+  Flags<[CC1Option]>, Group<m_Group>;
 def mips16 : Flag<["-"], "mips16">, Group<m_mips_Features_Group>;
 def mno_mips16 : Flag<["-"], "mno-mips16">, Group<m_mips_Features_Group>;
 def mmicromips : Flag<["-"], "mmicromips">, Group<m_mips_Features_Group>;
Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -113,6 +113,7 @@
 CODEGENOPT(InstrumentForProfiling , 1, 0) ///< Set when -pg is enabled.
 CODEGENOPT(CallFEntry , 1, 0) ///< Set when -mfentry is enabled.
 CODEGENOPT(MNopMCount , 1, 0) ///< Set when -mnop-mcount is enabled.
+CODEGENOPT(PackedStack , 1, 0) ///< Set when -mpacked-stack is enabled.
 CODEGENOPT(LessPreciseFPMAD  , 1, 0) ///< Enable less precise MAD instructions to
                                      ///< be generated.
 CODEGENOPT(PrepareForLTO     , 1, 0) ///< Set when -flto is enabled on the


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