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

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
```

Reviewed By: StephenFan

Differential Revision: https://reviews.llvm.org/D117975

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

@@ -44,6 +44,13 @@ enum EdgeKind_riscv : Edge::Kind {
   ///
   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

llvm/lib/ExecutionEngine/JITLink/ELF_riscv.cpp

@@ -220,6 +220,20 @@ private:
       *(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;
@@ -409,6 +423,8 @@ private:
       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:

llvm/lib/ExecutionEngine/JITLink/riscv.cpp

@@ -26,6 +26,8 @@ const char *getEdgeKindName(Edge::Kind K) {
     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:

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

@@ -0,0 +1,37 @@
+# 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