[RISCV] Implement getExprForFDESymbol to ensure RISCV_32_PCREL is used for the FDE location
Follow binutils in using RISCV_32_PCREL for the FDE initial location. As
explained in the relevant binutils commit
<https://github.com/riscv/riscv-binutils-gdb/commit/a6cbf936e3dce68114d28cdf60d510a3f78a6d40>,
the ADD/SUB pair of relocations is problematic in the presence of linker
relaxation.
This patch has the same end goal as D64715 but includes test changes and
avoids adding a new global VariantKind to MCExpr.h (preferring
RISCVMCExpr VKs like the rest of the RISC-V backend).
Differential Revision: https://reviews.llvm.org/D66419
llvm-svn: 369375
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
index 9c180a5..1122f27 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFObjectWriter.cpp
@@ -7,6 +7,7 @@
//===----------------------------------------------------------------------===//
#include "MCTargetDesc/RISCVFixupKinds.h"
+#include "MCTargetDesc/RISCVMCExpr.h"
#include "MCTargetDesc/RISCVMCTargetDesc.h"
#include "llvm/MC/MCELFObjectWriter.h"
#include "llvm/MC/MCFixup.h"
@@ -47,6 +48,7 @@
const MCValue &Target,
const MCFixup &Fixup,
bool IsPCRel) const {
+ const MCExpr *Expr = Fixup.getValue();
// Determine the type of the relocation
unsigned Kind = Fixup.getKind();
if (IsPCRel) {
@@ -87,6 +89,9 @@
default:
llvm_unreachable("invalid fixup kind!");
case FK_Data_4:
+ if (Expr->getKind() == MCExpr::Target &&
+ cast<RISCVMCExpr>(Expr)->getKind() == RISCVMCExpr::VK_RISCV_32_PCREL)
+ return ELF::R_RISCV_32_PCREL;
return ELF::R_RISCV_32;
case FK_Data_8:
return ELF::R_RISCV_64;