From 29c52f7449a3997329603ced247453221cbfb217 Mon Sep 17 00:00:00 2001
From: David Majnemer <david.majnemer@gmail.com>
Date: Tue, 6 Jan 2015 07:12:52 +0000
Subject: [PATCH] X86: Don't make illegal GOTTPOFF relocations

"ELF Handling for Thread-Local Storage" specifies that R_X86_64_GOTTPOFF
relocation target a movq or addq instruction.

Prohibit the truncation of such loads to movl or addl.

This fixes PR22083.

Differential Revision: http://reviews.llvm.org/D6839

llvm-svn: 225250
---
 llvm/lib/Target/X86/X86ISelLowering.cpp | 12 ++++++++++++
 llvm/lib/Target/X86/X86ISelLowering.h   |  5 +++++
 llvm/test/CodeGen/X86/tls-models.ll     |  8 ++++++++
 3 files changed, 25 insertions(+)

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 9e06861..9893589 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -3862,6 +3862,18 @@ bool X86TargetLowering::isFPImmLegal(const APFloat &Imm, EVT VT) const {
   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,
diff --git a/llvm/lib/Target/X86/X86ISelLowering.h b/llvm/lib/Target/X86/X86ISelLowering.h
index 0b01bae..ba077a8a 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.h
+++ b/llvm/lib/Target/X86/X86ISelLowering.h
@@ -770,6 +770,11 @@ namespace llvm {
       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;
     }
diff --git a/llvm/test/CodeGen/X86/tls-models.ll b/llvm/test/CodeGen/X86/tls-models.ll
index 8e3e958..0fd7853 100644
--- a/llvm/test/CodeGen/X86/tls-models.ll
+++ b/llvm/test/CodeGen/X86/tls-models.ll
@@ -128,6 +128,14 @@ entry:
   ; DARWIN:  _internal_ie@TLVP
 }
 
+define i32 @PR22083() {
+entry:
+  ret i32 ptrtoint (i32* @external_ie to i32)
+  ; X64-LABEL:     PR22083:
+  ; X64:     movq    external_ie@GOTTPOFF(%rip), %rax
+  ; X64_PIC-LABEL: PR22083:
+  ; X64_PIC: movq    external_ie@GOTTPOFF(%rip), %rax
+}
 
 ; ----- localexec specified -----
 
-- 
2.7.4