[JITLink][RISCV] fix the extractBits behavior and add R_RISCV_JAL relocation.

[fourdim]

Summary

This patch supports the R_RISCV_JAL relocation.
Moreover, it will fix the extractBits function's behavior as it extracts Size + 1 bits.
In the test ELF_jal.s:
Before:

Hi: 4294836480
extractBits(Hi, 12, 8): 480

After:

Hi: 4294836480
extractBits(Hi, 12, 8): 224

[StephenFan]

llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp

229

I think R_RISCV_JAL don't need to left shift Value 12 bits.

[jrtc27]

Why is it so hard to go read the LLD code. This is clearly wrong. LLD:

case R_RISCV_JAL: {
  checkInt(loc, static_cast<int64_t>(val) >> 1, 20, rel);
  checkAlignment(loc, val, 2, rel);

  uint32_t insn = read32le(loc) & 0xFFF;
  uint32_t imm20 = extractBits(val, 20, 20) << 31;
  uint32_t imm10_1 = extractBits(val, 10, 1) << 21;
  uint32_t imm11 = extractBits(val, 11, 11) << 20;
  uint32_t imm19_12 = extractBits(val, 19, 12) << 12;
  insn |= imm20 | imm10_1 | imm11 | imm19_12;

  write32le(loc, insn);
  return;
}

[fourdim]

address the comments and include the recent commits.

[fourdim]

Sorry about arc diff issue. I will update it later.

[fourdim]

fix the arc diff issue

[jrtc27]

This comment has been deleted.

llvm/include/llvm/ExecutionEngine/JITLink/riscv.h

47–51

This is still all wrong

[jrtc27]

Whoops Phab did its weird thing of forgetting I had already submitted a comment so it got submitted again alongside my new comment

[fourdim]

Address the comments.

[fourdim]

Reverted in the https://github.com/llvm/llvm-project/commit/051f7cdcd2ccfb54f5030e16d0026057d203ddd2 due to build failure.

[fourdim]

Include the recent commits and fix the test.

llvm/include/llvm/ExecutionEngine/JITLink/riscv.h

enum EdgeKind_riscv : Edge::Kind {
 
   /// PC-relative branch pointer value relocation
   ///
   /// Fixup expression:
   ///   Fixup <- (Target - Fixup + Addend)
   ///
   R_RISCV_BRANCH,
 
+  /// High 20 bits of PC-relative jump pointer value relocation
+  ///
+  /// Fixup expression:
+  ///   Fixup <- Target - Fixup + Addend
+  ///
+  R_RISCV_JAL,
+
   /// High 20 bits of 32-bit pointer value relocation
   ///
   /// Fixup expression
   ///   Fixup <- (Target + Addend + 0x800) >> 12
   R_RISCV_HI20,
 
   /// Low 12 bits of 32-bit pointer value relocation
   ///

llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp

case R_RISCV_BRANCH: {
       uint32_t Imm31_25 =
           extractBits(Value, 5, 6) << 25 | extractBits(Value, 12, 1) << 31;
       uint32_t Imm11_7 =
           extractBits(Value, 1, 4) << 8 | extractBits(Value, 11, 1) << 7;
       uint32_t RawInstr = *(little32_t *)FixupPtr;
       *(little32_t *)FixupPtr = (RawInstr & 0x1FFF07F) | Imm31_25 | Imm11_7;
       break;
     }
+    case R_RISCV_JAL: {
+      int64_t Value = E.getTarget().getAddress() + E.getAddend() - FixupAddress;
+      Error AlignmentIssue = checkAlignment(FixupAddress, Value, 2, E);
+      if (AlignmentIssue) {
+        return AlignmentIssue;
+      }
+      uint32_t Imm20 = extractBits(Value, 20, 1) << 31;
+      uint32_t Imm10_1 = extractBits(Value, 1, 10) << 21;
+      uint32_t Imm11 = extractBits(Value, 11, 1) << 20;
+      uint32_t Imm19_12 = extractBits(Value, 12, 8) << 12;
+      uint32_t RawInstr = *(little32_t *)FixupPtr;
+      *(little32_t *)FixupPtr = RawInstr | Imm20 | Imm10_1 | Imm11 | Imm19_12;
+      break;
+    }
     case R_RISCV_HI20: {
       int64_t Value = (E.getTarget().getAddress() + E.getAddend()).getValue();
       int64_t Hi = Value + 0x800;
       if (LLVM_UNLIKELY(!isInRangeForImmS32(Hi)))
         return makeTargetOutOfRangeError(G, B, E);
       uint32_t RawInstr = *(little32_t *)FixupPtr;
       *(little32_t *)FixupPtr =
           (RawInstr & 0xFFF) | (static_cast<uint32_t>(Hi & 0xFFFFF000));
getRelocationKind(const uint32_t Type) {
     using namespace riscv;
     switch (Type) {
     case ELF::R_RISCV_32:
       return EdgeKind_riscv::R_RISCV_32;
     case ELF::R_RISCV_64:
       return EdgeKind_riscv::R_RISCV_64;
     case ELF::R_RISCV_BRANCH:
       return EdgeKind_riscv::R_RISCV_BRANCH;
+    case ELF::R_RISCV_JAL:
+      return EdgeKind_riscv::R_RISCV_JAL;
     case ELF::R_RISCV_HI20:
       return EdgeKind_riscv::R_RISCV_HI20;
     case ELF::R_RISCV_LO12_I:
       return EdgeKind_riscv::R_RISCV_LO12_I;
     case ELF::R_RISCV_CALL:
       return EdgeKind_riscv::R_RISCV_CALL;
     case ELF::R_RISCV_PCREL_HI20:
       return EdgeKind_riscv::R_RISCV_PCREL_HI20;

llvm/lib/ExecutionEngine/JITLink/riscv.cpp

 const char *getEdgeKindName(Edge::Kind K) {
   switch (K) {
   case R_RISCV_32:
     return "R_RISCV_32";
   case R_RISCV_64:
     return "R_RISCV_64";
   case R_RISCV_BRANCH:
     return "R_RISCV_BRANCH";
+  case R_RISCV_JAL:
+    return "R_RISCV_JAL";
   case R_RISCV_HI20:
     return "R_RISCV_HI20";
   case R_RISCV_LO12_I:
     return "R_RISCV_LO12_I";
   case R_RISCV_PCREL_HI20:
     return "R_RISCV_PCREL_HI20";
   case R_RISCV_PCREL_LO12_I:
     return "R_RISCV_PCREL_LO12_I";

llvm/test/ExecutionEngine/JITLink/RISCV/ELF_jal.s

+# RUN: rm -rf %t && mkdir -p %t
+# RUN: llvm-mc -triple=riscv64 -filetype=obj \
+# RUN:     -o %t/elf_riscv64_jal.o %s
+# RUN: llvm-mc -triple=riscv32 -filetype=obj \
+# RUN:     -o %t/elf_riscv32_jal.o %s
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x1ff00000 -slab-page-size 4096 \
+# RUN:     -abs external_func=0x1fe000fe \
+# RUN:     -check %s %t/elf_riscv64_jal.o
+# RUN: llvm-jitlink -noexec \
+# RUN:     -slab-allocate 100Kb -slab-address 0x1ff00000 -slab-page-size 4096 \
+# RUN:     -abs external_func=0x1fe000fe \
+# RUN:     -check %s %t/elf_riscv32_jal.o
+#
+
+        .text
+        .file   "testcase.c"
+
+# Empty main entry point.
+        .globl  main
+        .p2align  1
+        .type   main,@function
+main:
+        ret
+
+        .size   main, .-main
+
+# Test R_RISCV_JAL
+
+# jitlink-check: decode_operand(test_jal, 1)[31:12] = (external_func - test_jal)[31:12]
+  .globl  test_jal
+  .p2align  1
+  .type  test_jal,@function
+test_jal:
+  jal x0, external_func
+
+  .size test_jal, .-test_jal