From 69d1c115dbae9ffdfd85b8bb29e15a2c8092e553 Mon Sep 17 00:00:00 2001
From: Akira Hatanaka <ahatanaka@mips.com>
Date: Wed, 24 Jul 2013 01:58:40 +0000
Subject: [PATCH] [mips] Use pristine object file while processing relocations.

    Similar to ARM change r182800, dynamic linker will read bits/addends from
    the original object rather than from the object that might have been patched
    previously. For the purpose of relocations for MCJIT stubs on MIPS, we
    internally use otherwise unused MIPS relocations.

    The change also enables MCJIT unit tests for MIPS (EL/BE), and the following
    two tests now pass:

    - MCJITTest.return_global and
    - MCJITTest.multiple_functions.

    These issues have been tracked as Bug 16250.

    Patch by Petar Jovanovic.

llvm-svn: 187019
---
 include/llvm/Object/ELF.h                     |  2 ++
 include/llvm/Support/ELF.h                    |  2 ++
 .../RuntimeDyld/RuntimeDyldELF.cpp            | 27 ++++++++++++++-----
 .../ExecutionEngine/MCJIT/MCJITTestBase.h     |  2 ++
 4 files changed, 26 insertions(+), 7 deletions(-)

diff --git a/include/llvm/Object/ELF.h b/include/llvm/Object/ELF.h
index c5c18a0666a..a14d1680342 100644
--- a/include/llvm/Object/ELF.h
+++ b/include/llvm/Object/ELF.h
@@ -1666,6 +1666,8 @@ StringRef ELFObjectFile<ELFT>::getRelocationTypeName(uint32_t Type) const {
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_PC16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_CALL16);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_GPREL32);
+      LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_UNUSED1);
+      LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_UNUSED2);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_SHIFT5);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_SHIFT6);
       LLVM_ELF_SWITCH_RELOC_TYPE_NAME(R_MIPS_64);
diff --git a/include/llvm/Support/ELF.h b/include/llvm/Support/ELF.h
index d53ebdbfb91..c32724054fd 100644
--- a/include/llvm/Support/ELF.h
+++ b/include/llvm/Support/ELF.h
@@ -868,6 +868,8 @@ enum {
   R_MIPS_PC16              = 10,
   R_MIPS_CALL16            = 11,
   R_MIPS_GPREL32           = 12,
+  R_MIPS_UNUSED1           = 13,
+  R_MIPS_UNUSED2           = 14,
   R_MIPS_SHIFT5            = 16,
   R_MIPS_SHIFT6            = 17,
   R_MIPS_64                = 18,
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
index cb3b5129f23..05cb5f83bed 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp
@@ -456,6 +456,8 @@ void RuntimeDyldELF::resolveMIPSRelocation(const SectionEntry &Section,
                                            uint32_t Value,
                                            uint32_t Type,
                                            int32_t Addend) {
+  uint32_t *Placeholder = reinterpret_cast<uint32_t*>(Section.ObjAddress +
+                                                      Offset);
   uint32_t* TargetPtr = (uint32_t*)(Section.Address + Offset);
   Value += Addend;
 
@@ -473,19 +475,30 @@ void RuntimeDyldELF::resolveMIPSRelocation(const SectionEntry &Section,
     llvm_unreachable("Not implemented relocation type!");
     break;
   case ELF::R_MIPS_32:
-    *TargetPtr = Value + (*TargetPtr);
+    *TargetPtr = Value + (*Placeholder);
     break;
   case ELF::R_MIPS_26:
-    *TargetPtr = ((*TargetPtr) & 0xfc000000) | (( Value & 0x0fffffff) >> 2);
+    *TargetPtr = ((*Placeholder) & 0xfc000000) | (( Value & 0x0fffffff) >> 2);
     break;
   case ELF::R_MIPS_HI16:
     // Get the higher 16-bits. Also add 1 if bit 15 is 1.
-    Value += ((*TargetPtr) & 0x0000ffff) << 16;
+    Value += ((*Placeholder) & 0x0000ffff) << 16;
+    *TargetPtr = ((*Placeholder) & 0xffff0000) |
+                 (((Value + 0x8000) >> 16) & 0xffff);
+    break;
+  case ELF::R_MIPS_LO16:
+    Value += ((*Placeholder) & 0x0000ffff);
+    *TargetPtr = ((*Placeholder) & 0xffff0000) | (Value & 0xffff);
+    break;
+  case ELF::R_MIPS_UNUSED1:
+    // Similar to ELF::R_ARM_PRIVATE_0, R_MIPS_UNUSED1 and R_MIPS_UNUSED2
+    // are used for internal JIT purpose. These relocations are similar to
+    // R_MIPS_HI16 and R_MIPS_LO16, but they do not take any addend into
+    // account.
     *TargetPtr = ((*TargetPtr) & 0xffff0000) |
                  (((Value + 0x8000) >> 16) & 0xffff);
     break;
-   case ELF::R_MIPS_LO16:
-    Value += ((*TargetPtr) & 0x0000ffff);
+  case ELF::R_MIPS_UNUSED2:
     *TargetPtr = ((*TargetPtr) & 0xffff0000) | (Value & 0xffff);
     break;
    }
@@ -954,10 +967,10 @@ void RuntimeDyldELF::processRelocationRef(unsigned SectionID,
       // Creating Hi and Lo relocations for the filled stub instructions.
       RelocationEntry REHi(SectionID,
                            StubTargetAddr - Section.Address,
-                           ELF::R_MIPS_HI16, Value.Addend);
+                           ELF::R_MIPS_UNUSED1, Value.Addend);
       RelocationEntry RELo(SectionID,
                            StubTargetAddr - Section.Address + 4,
-                           ELF::R_MIPS_LO16, Value.Addend);
+                           ELF::R_MIPS_UNUSED2, Value.Addend);
 
       if (Value.SymbolName) {
         addRelocationForSymbol(REHi, Value.SymbolName);
diff --git a/unittests/ExecutionEngine/MCJIT/MCJITTestBase.h b/unittests/ExecutionEngine/MCJIT/MCJITTestBase.h
index 9766a79ae52..5debb8b5785 100644
--- a/unittests/ExecutionEngine/MCJIT/MCJITTestBase.h
+++ b/unittests/ExecutionEngine/MCJIT/MCJITTestBase.h
@@ -156,6 +156,8 @@ protected:
     // kept in sync.
     SupportedArchs.push_back(Triple::aarch64);
     SupportedArchs.push_back(Triple::arm);
+    SupportedArchs.push_back(Triple::mips);
+    SupportedArchs.push_back(Triple::mipsel);
     SupportedArchs.push_back(Triple::x86);
     SupportedArchs.push_back(Triple::x86_64);