[llvm] r233119 - AArch64: use a different means to determine whether to byte swap relocations.

[Peter Collingbourne]

Author: pcc
Date: Tue Mar 24 16:47:03 2015
New Revision: 233119

URL: http://llvm.org/viewvc/llvm-project?rev=233119&view=rev
Log:
AArch64: use a different means to determine whether to byte swap relocations.

This code depended on a bug in the FindAssociatedSection function that would
cause it to return the wrong result for certain absolute expressions. Instead,
use EvaluateAsRelocatable.

Modified:
    llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp

Modified: llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp?rev=233119&r1=233118&r2=233119&view=diff
==============================================================================
--- llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp (original)
+++ llvm/trunk/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp Tue Mar 24 16:47:03 2015
@@ -18,6 +18,7 @@
 #include "llvm/MC/MCObjectWriter.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCSectionMachO.h"
+#include "llvm/MC/MCValue.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MachO.h"
 using namespace llvm;
@@ -493,14 +494,28 @@ void ELFAArch64AsmBackend::processFixupV
     IsResolved = false;
 }
 
+// Returns whether this fixup is based on an address in the .eh_frame section,
+// and therefore should be byte swapped.
+// FIXME: Should be replaced with something more principled.
+static bool isByteSwappedFixup(const MCExpr *E) {
+  MCValue Val;
+  if (!E->EvaluateAsRelocatable(Val, nullptr, nullptr))
+    return false;
+
+  if (!Val.getSymA() || Val.getSymA()->getSymbol().isUndefined())
+    return false;
+
+  const MCSectionELF *SecELF =
+      dyn_cast<MCSectionELF>(&Val.getSymA()->getSymbol().getSection());
+  return SecELF->getSectionName() == ".eh_frame";
+}
+
 void ELFAArch64AsmBackend::applyFixup(const MCFixup &Fixup, char *Data,
                                       unsigned DataSize, uint64_t Value,
                                       bool IsPCRel) const {
   // store fixups in .eh_frame section in big endian order
   if (!IsLittleEndian && Fixup.getKind() == FK_Data_4) {
-    const MCSection *Sec = Fixup.getValue()->FindAssociatedSection();
-    const MCSectionELF *SecELF = dyn_cast_or_null<const MCSectionELF>(Sec);
-    if (SecELF && SecELF->getSectionName() == ".eh_frame")
+    if (isByteSwappedFixup(Fixup.getValue()))
       Value = ByteSwap_32(unsigned(Value));
   }
   AArch64AsmBackend::applyFixup (Fixup, Data, DataSize, Value, IsPCRel);