[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.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187019 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 26 insertions, 7 deletions

diff --git a/include/llvm/Object/ELF.h b/include/llvm/Object/ELF.h
index c5c18a0..a14d168 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 d53ebdb..c327240 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 cb3b512..05cb5f8 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 9766a79..5debb8b 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);