[PATCH] Emit ABI_PCS_R9_use build attribute.

[Benjamin Foster]

Emit the build attribute describing how the r9 register is to be treated, (i.e. as V6 or not at all).

http://reviews.llvm.org/D4657

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 +146,10 @@
   AllowNeon2 = 2,     // SIMDv2 was permitted (Half-precision FP, MAC operations)
   AllowNeonARMv8 = 3, // ARM v8-A SIMD was permitted
 
+  // Tag_ABI_PCS_R9_use, (=14), uleb128
+  R9UsedAsV6 = 0, // R9 used as v6 (just another callee-saved register)
+  R9Reserved = 3, // R9 not used at all by code associated with attributed entity
+
   // Tag_ABI_PCS_RW_data, (=15), uleb128
   AddressRWPCRel = 1, // Address RW static data PC-relative
   AddressRWSBRel = 2, // Address RW static data SB-relative
Index: lib/Target/ARM/ARMAsmPrinter.cpp
===================================================================
--- lib/Target/ARM/ARMAsmPrinter.cpp
+++ lib/Target/ARM/ARMAsmPrinter.cpp
@@ -757,6 +757,15 @@
     }
   }
 
+  // ABI_PCS_R9_use, we only support either reserving the register, or treating
+  // it as another callee-saved register, but not as SB or a TLS pointer.
+  if (Subtarget->isR9Reserved())
+      ATS.emitAttribute(ARMBuildAttrs::ABI_PCS_R9_use,
+                        ARMBuildAttrs::R9Reserved);
+  else
+      ATS.emitAttribute(ARMBuildAttrs::ABI_PCS_R9_use,
+                        ARMBuildAttrs::R9UsedAsV6);
+
   if (Subtarget->hasTrustZone() && Subtarget->hasVirtualization())
       ATS.emitAttribute(ARMBuildAttrs::Virtualization_use,
                         ARMBuildAttrs::AllowTZVirtualization);
Index: test/CodeGen/ARM/build-attributes.ll
===================================================================
--- test/CodeGen/ARM/build-attributes.ll
+++ test/CodeGen/ARM/build-attributes.ll
@@ -38,6 +38,8 @@
 ; 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
+; RUN: llc < %s -mtriple=arm-none-linux-gnueabi | FileCheck %s --check-prefix=PCS-R9-USE
+; RUN: llc < %s -mtriple=arm-none-linux-gnueabi -arm-reserve-r9 | FileCheck %s --check-prefix=PCS-R9-RESERVE
 
 ; XSCALE:      .eabi_attribute 6, 5
 ; XSCALE:      .eabi_attribute 8, 1
@@ -463,6 +465,9 @@
 ; RELOC-PIC:  .eabi_attribute 17, 2
 ; RELOC-OTHER:  .eabi_attribute 17, 1
 
+; PCS-R9-USE:  .eabi_attribute 14, 0
+; PCS-R9-RESERVE:  .eabi_attribute 14, 3
+
 define i32 @f(i64 %z) {
 	ret i32 0
 }
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