1 files changed, 82 insertions, 0 deletions
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp
index ad8357f9cfc..53648a5922c 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVMCExpr.cpp
@@ -14,6 +14,7 @@
 
 #include "RISCV.h"
 #include "RISCVMCExpr.h"
+#include "RISCVFixupKinds.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCStreamer.h"
@@ -40,9 +41,90 @@ void RISCVMCExpr::printImpl(raw_ostream &OS, const MCAsmInfo *MAI) const {
     OS << ')';
 }
 
+const MCFixup *RISCVMCExpr::getPCRelHiFixup() const {
+  MCValue AUIPCLoc;
+  if (!getSubExpr()->evaluateAsRelocatable(AUIPCLoc, nullptr, nullptr))
+    return nullptr;
+
+  const MCSymbolRefExpr *AUIPCSRE = AUIPCLoc.getSymA();
+  if (!AUIPCSRE)
+    return nullptr;
+
+  const auto *DF =
+      dyn_cast_or_null<MCDataFragment>(AUIPCSRE->findAssociatedFragment());
+  if (!DF)
+    return nullptr;
+
+  const MCSymbol *AUIPCSymbol = &AUIPCSRE->getSymbol();
+  for (const MCFixup &F : DF->getFixups()) {
+    if (F.getOffset() != AUIPCSymbol->getOffset())
+      continue;
+
+    switch ((unsigned)F.getKind()) {
+    default:
+      continue;
+    case RISCV::fixup_riscv_pcrel_hi20:
+      return &F;
+    }
+  }
+
+  return nullptr;
+}
+
+bool RISCVMCExpr::evaluatePCRelLo(MCValue &Res, const MCAsmLayout *Layout,
+                                  const MCFixup *Fixup) const {
+  // VK_RISCV_PCREL_LO has to be handled specially.  The MCExpr inside is
+  // actually the location of a auipc instruction with a VK_RISCV_PCREL_HI fixup
+  // pointing to the real target.  We need to generate an MCValue in the form of
+  // (<real target> + <offset from this fixup to the auipc fixup>).  The Fixup
+  // is pcrel relative to the VK_RISCV_PCREL_LO fixup, so we need to add the
+  // offset to the VK_RISCV_PCREL_HI Fixup from VK_RISCV_PCREL_LO to correct.
+  MCValue AUIPCLoc;
+  if (!getSubExpr()->evaluateAsValue(AUIPCLoc, *Layout))
+    return false;
+
+  const MCSymbolRefExpr *AUIPCSRE = AUIPCLoc.getSymA();
+  // Don't try to evaluate %pcrel_hi/%pcrel_lo pairs that cross fragment
+  // boundries.
+  if (!AUIPCSRE ||
+      findAssociatedFragment() != AUIPCSRE->findAssociatedFragment())
+    return false;
+
+  const MCSymbol *AUIPCSymbol = &AUIPCSRE->getSymbol();
+  if (!AUIPCSymbol)
+    return false;
+
+  const MCFixup *TargetFixup = getPCRelHiFixup();
+  if (!TargetFixup)
+    return false;
+
+  if ((unsigned)TargetFixup->getKind() != RISCV::fixup_riscv_pcrel_hi20)
+    return false;
+
+  MCValue Target;
+  if (!TargetFixup->getValue()->evaluateAsValue(Target, *Layout))
+    return false;
+
+  if (!Target.getSymA() || !Target.getSymA()->getSymbol().isInSection())
+    return false;
+
+  if (&Target.getSymA()->getSymbol().getSection() !=
+      findAssociatedFragment()->getParent())
+    return false;
+
+  uint64_t AUIPCOffset = AUIPCSymbol->getOffset();
+
+  Res = MCValue::get(Target.getSymA(), nullptr,
+                     Target.getConstant() + (Fixup->getOffset() - AUIPCOffset));
+  return true;
+}
+
 bool RISCVMCExpr::evaluateAsRelocatableImpl(MCValue &Res,
                                             const MCAsmLayout *Layout,
                                             const MCFixup *Fixup) const {
+  if (Kind == VK_RISCV_PCREL_LO && evaluatePCRelLo(Res, Layout, Fixup))
+    return true;
+
   if (!getSubExpr()->evaluateAsRelocatable(Res, Layout, Fixup))
     return false;