[PATCH] D42216: Use New Module Metadata String "AvoidPLT" to avoid calls via PLT

[Rafael Avila de Espindola via llvm-commits]

A LGTM on the list is all you need.

LGTM :-)

Thanks,
Rafael

Sriraman Tallam via Phabricator <reviews at reviews.llvm.org> writes:

> tmsriram updated this revision to Diff 135114.
> tmsriram added a comment.
>
> Patch updated.
>
>
> https://reviews.llvm.org/D42216
>
> Files:
>   include/llvm/IR/Module.h
>   lib/IR/Module.cpp
>   lib/Target/X86/X86ISelLowering.cpp
>   lib/Target/X86/X86Subtarget.cpp
>   test/CodeGen/X86/no-plt.ll
>
> Index: test/CodeGen/X86/no-plt.ll
> ===================================================================
> --- test/CodeGen/X86/no-plt.ll
> +++ test/CodeGen/X86/no-plt.ll
> @@ -3,6 +3,18 @@
>  ; RUN: llc < %s -mcpu=generic -mtriple=x86_64-linux-gnu \
>  ; RUN:   | FileCheck -check-prefix=X64 --check-prefix=STATIC %s
>  
> +define void @memset_call(i8* nocapture %a, i8 %c, i32 %n) {
> +; X64: callq *memset at GOTPCREL(%rip)
> +  call void @llvm.memset.p0i8.i32(i8* %a, i8 %c, i32 %n, i1 false)
> +  ret void
> +}
> +
> +define void @memcpy_call(i8* nocapture %a, i8* nocapture readonly %b, i64 %n) {
> +; X64: callq *memcpy at GOTPCREL(%rip)
> +  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %a, i8* %b, i64 %n, i32 1, i1 false)
> +  ret void
> +}
> +
>  define i32 @main() {
>  ; X64:    callq *foo at GOTPCREL(%rip)
>  ; PIC:    callq bar at PLT
> @@ -20,3 +32,8 @@
>  declare i32 @foo() nonlazybind
>  declare i32 @bar()
>  declare hidden i32 @baz() nonlazybind
> +declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture writeonly, i8* nocapture readonly, i64, i32, i1)
> +declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i1)
> +
> +!llvm.module.flags = !{!1}
> +!1 = !{i32 7, !"RtLibUseGOT", i32 1}
> Index: lib/Target/X86/X86Subtarget.cpp
> ===================================================================
> --- lib/Target/X86/X86Subtarget.cpp
> +++ lib/Target/X86/X86Subtarget.cpp
> @@ -157,8 +157,11 @@
>        // In Regcall calling convention those registers are used for passing
>        // parameters. Thus we need to prevent lazy binding in Regcall.
>        return X86II::MO_GOTPCREL;
> -    if (F && F->hasFnAttribute(Attribute::NonLazyBind) && is64Bit())
> -      return X86II::MO_GOTPCREL;
> +    // If PLT must be avoided then the call should be via GOTPCREL.
> +    if (((F && F->hasFnAttribute(Attribute::NonLazyBind)) ||
> +         (!F && M.getRtLibUseGOT())) &&
> +        is64Bit())
> +       return X86II::MO_GOTPCREL;
>      return X86II::MO_PLT;
>    }
>  
> Index: lib/Target/X86/X86ISelLowering.cpp
> ===================================================================
> --- lib/Target/X86/X86ISelLowering.cpp
> +++ lib/Target/X86/X86ISelLowering.cpp
> @@ -3772,6 +3772,14 @@
>  
>      Callee = DAG.getTargetExternalSymbol(
>          S->getSymbol(), getPointerTy(DAG.getDataLayout()), OpFlags);
> +
> +    if (OpFlags == X86II::MO_GOTPCREL) {
> +      Callee = DAG.getNode(X86ISD::WrapperRIP, dl,
> +          getPointerTy(DAG.getDataLayout()), Callee);
> +      Callee = DAG.getLoad(
> +          getPointerTy(DAG.getDataLayout()), dl, DAG.getEntryNode(), Callee,
> +          MachinePointerInfo::getGOT(DAG.getMachineFunction()));
> +    }
>    } else if (Subtarget.isTarget64BitILP32() &&
>               Callee->getValueType(0) == MVT::i32) {
>      // Zero-extend the 32-bit Callee address into a 64-bit according to x32 ABI
> Index: lib/IR/Module.cpp
> ===================================================================
> --- lib/IR/Module.cpp
> +++ lib/IR/Module.cpp
> @@ -510,6 +510,15 @@
>    OwnedMemoryBuffer = std::move(MB);
>  }
>  
> +bool Module::getRtLibUseGOT() const {
> +  auto *Val = cast_or_null<ConstantAsMetadata>(getModuleFlag("RtLibUseGOT"));
> +  return Val && (cast<ConstantInt>(Val->getValue())->getZExtValue() > 0);
> +}
> +
> +void Module::setRtLibUseGOT() {
> +  addModuleFlag(ModFlagBehavior::Max, "RtLibUseGOT", 1);
> +}
> +
>  GlobalVariable *llvm::collectUsedGlobalVariables(
>      const Module &M, SmallPtrSetImpl<GlobalValue *> &Set, bool CompilerUsed) {
>    const char *Name = CompilerUsed ? "llvm.compiler.used" : "llvm.used";
> Index: include/llvm/IR/Module.h
> ===================================================================
> --- include/llvm/IR/Module.h
> +++ include/llvm/IR/Module.h
> @@ -838,6 +838,13 @@
>    Metadata *getProfileSummary();
>    /// @}
>  
> +  /// Returns true if PLT should be avoided for RTLib calls.
> +  bool getRtLibUseGOT() const;
> +
> +  /// Set that PLT should be avoid for RTLib calls.
> +  void setRtLibUseGOT();
> +
> +
>    /// Take ownership of the given memory buffer.
>    void setOwnedMemoryBuffer(std::unique_ptr<MemoryBuffer> MB);
>  };