[Mips] Implement R_MIPS_PC21_S2 relocation handling

llvm-svn: 232707

2 files changed, 66 insertions, 0 deletions

diff --git a/lld/lib/ReaderWriter/ELF/Mips/MipsRelocationHandler.cpp b/lld/lib/ReaderWriter/ELF/Mips/MipsRelocationHandler.cpp
index 28ffe1b60cf..358aae1e41a 100644
--- a/lld/lib/ReaderWriter/ELF/Mips/MipsRelocationHandler.cpp
+++ b/lld/lib/ReaderWriter/ELF/Mips/MipsRelocationHandler.cpp
@@ -65,6 +65,8 @@ static MipsRelocationParams getRelocationParams(uint32_t rType) {
   case R_MIPS_26:
   case LLD_R_MIPS_GLOBAL_26:
     return {4, 0x3ffffff, 2, false};
+  case R_MIPS_PC21_S2:
+    return {4, 0x1fffff, 2, false};
   case R_MIPS_HI16:
   case R_MIPS_LO16:
   case R_MIPS_GPREL16:
@@ -219,6 +221,14 @@ static uint32_t relocGPRel32(uint64_t S, int64_t A, uint64_t GP) {
   return result;
 }
 
+/// \brief R_MIPS_PC21_S2
+static uint32_t relocPc21(uint64_t P, uint64_t S, int64_t A) {
+  A = llvm::SignExtend32<23>(A);
+  // FIXME (simon): Check that S + A has 4-byte alignment
+  int32_t result = S + A - P;
+  return result >> 2;
+}
+
 /// \brief R_MICROMIPS_PC7_S1
 static uint32_t relocPc7(uint64_t P, uint64_t S, int64_t A) {
   A = llvm::SignExtend32<8>(A);
@@ -351,6 +361,8 @@ static ErrorOr<uint64_t> calculateRelocation(const Reference &ref,
     return relocGOT(tgtAddr, gpAddr);
   case R_MIPS_GOT_OFST:
     return relocGOTOfst(tgtAddr, ref.addend());
+  case R_MIPS_PC21_S2:
+    return relocPc21(relAddr, tgtAddr, ref.addend());
   case R_MICROMIPS_PC7_S1:
     return relocPc7(relAddr, tgtAddr, ref.addend());
   case R_MICROMIPS_PC10_S1:
diff --git a/lld/test/elf/Mips/rel-pc21-s2.test b/lld/test/elf/Mips/rel-pc21-s2.test
new file mode 100644
index 00000000000..44d840e94c3
--- /dev/null
+++ b/lld/test/elf/Mips/rel-pc21-s2.test
@@ -0,0 +1,54 @@
+# Check handling of R_MIPS_PC21_S2 relocation.
+
+# RUN: yaml2obj -format=elf %s > %t.o
+# RUN: lld -flavor gnu -target mipsel -e T0 -o %t.exe %t.o
+# RUN: llvm-objdump -s -t %t.exe | FileCheck %s
+
+# CHECK: Contents of section .text:
+# CHECK-NEXT: 400110 01000000 00000000 00000000
+#                    ^ V
+#                    A = -1 << 2 = -4 =>
+#                    V = (T1 - 4 - T0) >> 2 =>
+#                    V => 4 >> 2 = 1
+
+# CHECK: SYMBOL TABLE:
+# CHECK: 00400110 g  F .text  00000008 T0
+# CHECK: 00400118 g  F .text  00000004 T1
+
+FileHeader:
+  Class:   ELFCLASS32
+  Data:    ELFDATA2LSB
+  Type:    ET_REL
+  Machine: EM_MIPS
+  Flags:   [EF_MIPS_CPIC, EF_MIPS_ABI_O32, EF_MIPS_ARCH_32R6]
+
+Sections:
+- Name:         .text
+  Type:         SHT_PROGBITS
+  Content:      "ffff1f000000000000000000"
+#                                ^ T1
+#                ^ T0 A := 0x1fffff
+  AddressAlign: 16
+  Flags:        [ SHF_ALLOC, SHF_EXECINSTR ]
+
+- Name:         .rel.text
+  Type:         SHT_REL
+  Info:         .text
+  AddressAlign: 4
+  Relocations:
+    - Offset: 0
+      Symbol: T1
+      Type:   R_MIPS_PC21_S2
+
+Symbols:
+  Global:
+    - Name:    T0
+      Section: .text
+      Type:    STT_FUNC
+      Value:   0
+      Size:    8
+    - Name:    T1
+      Section: .text
+      Type:    STT_FUNC
+      Value:   8
+      Size:    4