[PATCH] X86: Work around a bfd ld quirk wrt GOTTPOFF relocation processing

[David Majnemer]

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D6839

Files:
  llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
  llvm/trunk/lib/Target/X86/X86ISelLowering.h
  llvm/trunk/test/CodeGen/X86/tls-models.ll

Index: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
@@ -3862,6 +3862,18 @@
   return false;
 }
 
+bool X86TargetLowering::shouldReduceLoadWidth(SDNode *Load,
+                                              ISD::LoadExtType ExtTy,
+                                              EVT NewVT) const {
+  // "ELF Handling for Thread-Local Storage" specifies that R_X86_64_GOTTPOFF
+  // relocation target a movq or addq instruction: don't let the load shrink.
+  SDValue BasePtr = cast<LoadSDNode>(Load)->getBasePtr();
+  if (BasePtr.getOpcode() == X86ISD::WrapperRIP)
+    if (const auto *GA = dyn_cast<GlobalAddressSDNode>(BasePtr.getOperand(0)))
+      return GA->getTargetFlags() != X86II::MO_GOTTPOFF;
+  return true;
+}
+
 /// \brief Returns true if it is beneficial to convert a load of a constant
 /// to just the constant itself.
 bool X86TargetLowering::shouldConvertConstantLoadToIntImm(const APInt &Imm,
Index: llvm/trunk/lib/Target/X86/X86ISelLowering.h
===================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.h
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.h
@@ -770,6 +770,11 @@
       return !X86ScalarSSEf64 || VT == MVT::f80;
     }
 
+    /// Return true if we believe it is correct and profitable to reduce the
+    /// load node to a smaller type.
+    bool shouldReduceLoadWidth(SDNode *Load, ISD::LoadExtType ExtTy,
+                               EVT NewVT) const override;
+
     const X86Subtarget* getSubtarget() const {
       return Subtarget;
     }
Index: llvm/trunk/test/CodeGen/X86/tls-models.ll
===================================================================
--- llvm/trunk/test/CodeGen/X86/tls-models.ll
+++ llvm/trunk/test/CodeGen/X86/tls-models.ll
@@ -128,6 +128,14 @@
   ; DARWIN:  _internal_ie at TLVP
 }
 
+define i32 @PR22083() {
+entry:
+  ret i32 ptrtoint (i32* @external_ie to i32)
+  ; X64-LABEL:     PR22083:
+  ; X64:     movq    external_ie at GOTTPOFF(%rip), %rax
+  ; X64_PIC-LABEL: PR22083:
+  ; X64_PIC: movq    external_ie at GOTTPOFF(%rip), %rax
+}
 
 ; ----- localexec specified -----

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