reapply de872382 "[JITLink] Add anonymous symbols in LinkGraph..."

with fixes

This reapply `de872382`, which was
reverted in `fdb65785`

Add `# REQUIRES: asserts` in test file `anonymous_symbol.s` to disable
this test for non-debug build

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

@@ -79,6 +79,12 @@ enum EdgeKind_riscv : Edge::Kind {
   ///   Fixup <- (Target - Fixup + Addend)
   R_RISCV_CALL,
 
+  /// 32 bits PC relative relocation
+  ///
+  /// Fixup expression:
+  ///   Fixup <- (Target - Fixup + Addend)
+  R_RISCV_32_PCREL,
+
   /// PC relative GOT offset
   ///
   /// Fixup expression:
@@ -162,12 +168,6 @@ enum EdgeKind_riscv : Edge::Kind {
   /// Fixup expression:
   ///   Fixup <- (Target + Addend)
   R_RISCV_SET32,
-
-  /// Local label assignment
-  ///
-  /// Fixup expression:
-  ///   Fixup <- (Target - Fixup + Addend)
-  R_RISCV_32_PCREL,
 };
 
 /// Returns a string name for the given riscv edge. For debugging purposes

llvm/lib/ExecutionEngine/JITLink/ELFLinkGraphBuilder.h

@@ -441,11 +441,15 @@ template <typename ELFT> Error ELFLinkGraphBuilder<ELFT>::graphifySymbols() {
                  << "\"\n";
         });
 
-        // Model the section symbols as anonymous symbol.
+        // In RISCV, temporary symbols (Used to generate dwarf, eh_frame
+        // sections...) will appear in object code's symbol table, and LLVM does
+        // not use names on these temporary symbols (RISCV gnu toolchain uses
+        // names on these temporary symbols). If the symbol is unnamed, add an
+        // anonymous symbol.
         auto &GSym =
-            Sym.getType() == ELF::STT_SECTION
-                ? G->addAnonymousSymbol(*B, Sym.getValue(), Sym.st_size, false,
-                                        false)
+            Name->empty()
+                ? G->addAnonymousSymbol(*B, Sym.getValue(), Sym.st_size,
+                                        false, false)
                 : G->addDefinedSymbol(*B, Sym.getValue(), *Name, Sym.st_size, L,
                                       S, Sym.getType() == ELF::STT_FUNC, false);
         setGraphSymbol(SymIndex, GSym);

llvm/lib/ExecutionEngine/JITLink/riscv.cpp

@@ -38,6 +38,8 @@ const char *getEdgeKindName(Edge::Kind K) {
     return "R_RISCV_PCREL_LO12_S";
   case R_RISCV_CALL:
     return "R_RISCV_CALL";
+  case R_RISCV_32_PCREL:
+    return "R_RISCV_32_PCREL";
   case R_RISCV_ADD64:
     return "R_RISCV_ADD64";
   case R_RISCV_ADD32:
@@ -62,8 +64,6 @@ const char *getEdgeKindName(Edge::Kind K) {
     return "R_RISCV_SET16";
   case R_RISCV_SET32:
     return "R_RISCV_SET32";
-  case R_RISCV_32_PCREL:
-    return "R_RISCV_32_PCREL";
   }
   return getGenericEdgeKindName(K);
 }

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

+# REQUIRES: asserts
+# RUN: llvm-mc -triple=riscv64 -filetype=obj -o %t %s
+# RUN: llvm-jitlink -debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+#
+# Because of the exist of cfi directive, sections like eh_frame section will be emitted
+# in llvm's object code emission phase. Anonymous symbols will also be emitted to indicate
+# the section start and section end. So that by relocating these symbol, the section length
+# can be calculated.
+#
+# CHECK: Creating defined graph symbol for ELF symbol ""
+# CHECK: Creating defined graph symbol for ELF symbol ""
+        .text
+        .globl main
+        .p2align 2
+        .type main,@function
+main:
+        .cfi_startproc
+        ret
+        .Lfunc_end0:
+        .size main, .Lfunc_end0-main
+        .cfi_endproc