[PATCH] D43158: [RISCV] Always emit a symbol for R_RISCV_PCREL_LO12_I.

[Michael Spencer via Phabricator via llvm-commits]

Bigcheese created this revision.
Bigcheese added reviewers: ahmedcharles, asb.
Herald added subscribers: kito-cheng, niosHD, sabuasal, apazos, jordy.potman.lists, simoncook, johnrusso, rbar.

riscv-ld mislinks if a section relative symbol is used instead.

I've reported this as a bug
(https://github.com/riscv/riscv-binutils-gdb/issues/138), but it may be
defined as requiring a symbol.

Depends on: https://reviews.llvm.org/D43157


https://reviews.llvm.org/D43158

Files:
  lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
  test/MC/RISCV/pcrel-hilo.s


Index: test/MC/RISCV/pcrel-hilo.s
===================================================================
--- test/MC/RISCV/pcrel-hilo.s
+++ test/MC/RISCV/pcrel-hilo.s
@@ -16,4 +16,4 @@
 # CHECK-INSTR: addi t1, t1, 0
 
 # CHECK-REL: 0x0 R_RISCV_PCREL_HI20 foo 0x0
-# CHECK-REL: 0x4 R_RISCV_PCREL_LO12_I .text 0x0
+# CHECK-REL: 0x4 R_RISCV_PCREL_LO12_I .Ltmp0 0x0
Index: lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
===================================================================
--- lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
+++ lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
@@ -23,6 +23,9 @@
 
   ~RISCVELFObjectWriter() override;
 
+  bool needsRelocateWithSymbol(const MCSymbol &Sym,
+                               unsigned Type) const override;
+
 protected:
   unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
                         const MCFixup &Fixup, bool IsPCRel) const override;
@@ -35,6 +38,13 @@
 
 RISCVELFObjectWriter::~RISCVELFObjectWriter() {}
 
+bool RISCVELFObjectWriter::needsRelocateWithSymbol(const MCSymbol &Sym,
+                                                   unsigned Type) const {
+  // riscv-ld depends on R_RISCV_PCREL_LO12_I directly targetting a symbol.
+  // See https://github.com/riscv/riscv-binutils-gdb/issues/138
+  return Type == ELF::R_RISCV_PCREL_LO12_I;
+}
+
 unsigned RISCVELFObjectWriter::getRelocType(MCContext &Ctx,
                                             const MCValue &Target,
                                             const MCFixup &Fixup,


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