[PATCH] [ARM] Emit correct build attributes for the different relocation models

[Asiri Rathnayake]

Generate build attributes:

  # Tag_ABI_PCS_RW_data
  # Tag_ABI_PCS_RO_data
  # Tag_ABI_PCS_GOT_use

Based on the selected relocation model.

http://reviews.llvm.org/D3918

Files:
  include/llvm/Support/ARMBuildAttributes.h
  lib/Target/ARM/ARMAsmPrinter.cpp
  test/CodeGen/ARM/build-attributes.ll

Index: include/llvm/Support/ARMBuildAttributes.h
===================================================================
--- include/llvm/Support/ARMBuildAttributes.h
+++ include/llvm/Support/ARMBuildAttributes.h
@@ -146,6 +146,19 @@
   AllowNeon2 = 2,     // SIMDv2 was permitted (Half-precision FP, MAC operations)
   AllowNeonARMv8 = 3, // ARM v8-A SIMD was permitted
 
+  // Tag_ABI_PCS_RW_data, (=15), uleb128
+  AddressRWPCRel = 1, // Permit PC-relative addressing of RW static data
+  AddressRWSBRel = 2, // Permit SB-relative addressing of RW static data
+  AddressRWNone = 3, // No RW static data permitted
+
+  // Tag_ABI_PCS_RO_data, (=14), uleb128
+  AddressROPCRel = 1, // Permit PC-relative addressing of RO static data
+  AddressRONone = 2, // No RO static data permitted
+
+  // Tag_ABI_PCS_GOT_use, (=17), uleb128
+  AddressDirect = 1, // Address imported data directly
+  AddressGOT = 2, // Address imported data indirectly (via GOT)
+
   // Tag_ABI_FP_denormal, (=20), uleb128
   PreserveFPSign = 2, // sign when flushed-to-zero is preserved
 
Index: lib/Target/ARM/ARMAsmPrinter.cpp
===================================================================
--- lib/Target/ARM/ARMAsmPrinter.cpp
+++ lib/Target/ARM/ARMAsmPrinter.cpp
@@ -671,6 +671,20 @@
       ATS.emitFPU(ARM::VFPV2);
   }
 
+  if (TM.getRelocationModel() == Reloc::PIC_) {
+    // PIC specific attributes.
+    ATS.emitAttribute(ARMBuildAttrs::ABI_PCS_RW_data,
+                      ARMBuildAttrs::AddressRWPCRel);
+    ATS.emitAttribute(ARMBuildAttrs::ABI_PCS_RO_data,
+                      ARMBuildAttrs::AddressROPCRel);
+    ATS.emitAttribute(ARMBuildAttrs::ABI_PCS_GOT_use,
+                      ARMBuildAttrs::AddressGOT);
+  } else {
+    // Allow direct addressing of imported data for all other relocation models.
+    ATS.emitAttribute(ARMBuildAttrs::ABI_PCS_GOT_use,
+                      ARMBuildAttrs::AddressDirect);
+  }
+
   // Signal various FP modes.
   if (!TM.Options.UnsafeFPMath) {
     ATS.emitAttribute(ARMBuildAttrs::ABI_FP_denormal, ARMBuildAttrs::Allowed);
Index: test/CodeGen/ARM/build-attributes.ll
===================================================================
--- test/CodeGen/ARM/build-attributes.ll
+++ test/CodeGen/ARM/build-attributes.ll
@@ -33,6 +33,11 @@
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=-vfp2,-vfp3,-vfp4,-neon | FileCheck %s --check-prefix=CORTEX-A7-NOFPU
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=+vfp4,-neon | FileCheck %s --check-prefix=CORTEX-A7-FPUV4
 ; RUN: llc < %s -mtriple=armv7-none-linux-gnueabi -mcpu=cortex-a7 -mattr=+vfp4,,+d16,-neon | FileCheck %s --check-prefix=CORTEX-A7-FPUV4
+; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -relocation-model=pic | FileCheck %s --check-prefix=RELOC-PIC
+; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -relocation-model=static | FileCheck %s --check-prefix=RELOC-OTHER
+; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -relocation-model=default | FileCheck %s --check-prefix=RELOC-OTHER
+; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -relocation-model=dynamic-no-pic | FileCheck %s --check-prefix=RELOC-OTHER
+; RUN: llc < %s -mtriple=arm-none-linux-gnueabi | FileCheck %s --check-prefix=RELOC-OTHER
 
 ; XSCALE:      .eabi_attribute 6, 5
 ; XSCALE:      .eabi_attribute 8, 1
@@ -453,6 +458,11 @@
 ; CORTEX-A57-NOT:  .eabi_attribute 44
 ; CORTEX-A57:  .eabi_attribute 68, 3
 
+; RELOC-PIC:  .eabi_attribute 15, 1
+; RELOC-PIC:  .eabi_attribute 16, 1
+; RELOC-PIC:  .eabi_attribute 17, 2
+; RELOC-OTHER:  .eabi_attribute 17, 1
+
 define i32 @f(i64 %z) {
 	ret i32 0
 }
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