From: Peter Collingbourne <peter@pcc.me.uk>
Date: Tue, 24 Mar 2015 21:47:03 +0000 (+0000)
Subject: AArch64: use a different means to determine whether to byte swap relocations.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4b8dfba3a128cb20c75fc7709d8c61a6af6e92a6;p=oota-llvm.git

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@233119 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp b/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
index 423da6500c4..84b63a0a8eb 100644
--- a/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
+++ b/lib/Target/AArch64/MCTargetDesc/AArch64AsmBackend.cpp
@@ -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::processFixupValue(
     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);