[llvm] r317292 - Avoid PLT for external calls when attribute nonlazybind is used.

[Sriraman Tallam via llvm-commits]

Author: tmsriram
Date: Thu Nov  2 17:10:19 2017
New Revision: 317292

URL: http://llvm.org/viewvc/llvm-project?rev=317292&view=rev
Log:
Avoid PLT for external calls when attribute nonlazybind is used.

Differential Revision: https://reviews.llvm.org/D39065

Added:
    llvm/trunk/test/CodeGen/X86/no-plt.ll
Modified:
    llvm/trunk/lib/Target/X86/X86Subtarget.cpp

Modified: llvm/trunk/lib/Target/X86/X86Subtarget.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86Subtarget.cpp?rev=317292&r1=317291&r2=317292&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86Subtarget.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86Subtarget.cpp Thu Nov  2 17:10:19 2017
@@ -144,6 +144,15 @@ X86Subtarget::classifyGlobalFunctionRefe
 unsigned char
 X86Subtarget::classifyGlobalFunctionReference(const GlobalValue *GV,
                                               const Module &M) const {
+  const Function *F = dyn_cast_or_null<Function>(GV);
+
+  // Do not use the PLT when explicitly told to do so for ELF 64-bit
+  // target.
+  if (isTargetELF() && is64Bit() && F &&
+      F->hasFnAttribute(Attribute::NonLazyBind) &&
+      GV->isDeclarationForLinker())
+    return X86II::MO_GOTPCREL;
+
   if (TM.shouldAssumeDSOLocal(M, GV))
     return X86II::MO_NO_FLAG;
 
@@ -153,8 +162,6 @@ X86Subtarget::classifyGlobalFunctionRefe
     return X86II::MO_DLLIMPORT;
   }
 
-  const Function *F = dyn_cast_or_null<Function>(GV);
-
   if (isTargetELF()) {
     if (is64Bit() && F && (CallingConv::X86_RegCall == F->getCallingConv()))
       // According to psABI, PLT stub clobbers XMM8-XMM15.

Added: llvm/trunk/test/CodeGen/X86/no-plt.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/no-plt.ll?rev=317292&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/no-plt.ll (added)
+++ llvm/trunk/test/CodeGen/X86/no-plt.ll Thu Nov  2 17:10:19 2017
@@ -0,0 +1,23 @@
+; RUN: llc < %s -mcpu=generic -mtriple=x86_64-linux-gnu -relocation-model=pic \
+; RUN:   | FileCheck -check-prefix=X64 %s
+; RUN: llc < %s -mcpu=generic -mtriple=x86_64-linux-gnu \
+; RUN:   | FileCheck -check-prefix=X64 %s
+
+define i32 @main() #0 {
+; X64: callq *_Z3foov at GOTPCREL(%rip)
+; X64: callq _Z3barv
+
+entry:
+  %retval = alloca i32, align 4
+  store i32 0, i32* %retval, align 4
+  %call1 = call i32 @_Z3foov()
+  %call2 = call i32 @_Z3barv()
+  ret i32 0
+}
+
+; Function Attrs: nonlazybind
+declare i32 @_Z3foov() #1
+
+declare i32 @_Z3barv() #2
+
+attributes #1 = { nonlazybind }