MC/Mach-O: Implement "absolutizing" semantics of .set, by evaluating the assembly time value of variables.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98241 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/MC/MCAssembler.cpp b/lib/MC/MCAssembler.cpp
index 21feeed..8d0075e 100644
--- a/lib/MC/MCAssembler.cpp
+++ b/lib/MC/MCAssembler.cpp
@@ -539,10 +539,10 @@
if (Target.isAbsolute()) { // constant
// SymbolNum of 0 indicates the absolute section.
//
- // FIXME: When is this generated?
+ // FIXME: Currently, these are never generated (see code below). I cannot
+ // find a case where they are actually emitted.
Type = RIT_Vanilla;
Value = 0;
- llvm_unreachable("FIXME: Not yet implemented!");
} else {
const MCSymbol *Symbol = Target.getSymA();
MCSymbolData *SD = &Asm.getSymbolData(*Symbol);
@@ -572,6 +572,12 @@
if (IsPCRel)
Fixup.FixedValue -= Address;
+ // If the target evaluates to a constant, we don't need a relocation. This
+ // occurs with absolutized expressions which are not resolved to constants
+ // until after relaxation.
+ if (Target.isAbsolute())
+ return;
+
// If this fixup is a vanilla PC relative relocation for a local label, we
// don't need a relocation.
//
diff --git a/lib/MC/MCExpr.cpp b/lib/MC/MCExpr.cpp
index e364069..0ca2ad8 100644
--- a/lib/MC/MCExpr.cpp
+++ b/lib/MC/MCExpr.cpp
@@ -8,11 +8,14 @@
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCAsmLayout.h"
+#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetAsmBackend.h"
using namespace llvm;
void MCExpr::print(raw_ostream &OS) const {
@@ -187,8 +190,23 @@
const MCSymbol &Sym = cast<MCSymbolRefExpr>(this)->getSymbol();
// Evaluate recursively if this is a variable.
- if (Sym.isVariable())
- return Sym.getValue()->EvaluateAsRelocatable(Res, Layout);
+ if (Sym.isVariable()) {
+ if (!Sym.getValue()->EvaluateAsRelocatable(Res, Layout))
+ return false;
+
+ // Absolutize symbol differences when we have a layout object and the
+ // target requests it.
+ if (Layout && Res.getSymB() &&
+ Layout->getAssembler().getBackend().hasAbsolutizedSet()) {
+ MCSymbolData &A = Layout->getAssembler().getSymbolData(*Res.getSymA());
+ MCSymbolData &B = Layout->getAssembler().getSymbolData(*Res.getSymB());
+ Res = MCValue::get(+ A.getFragment()->getAddress() + A.getOffset()
+ - B.getFragment()->getAddress() - B.getOffset()
+ + Res.getConstant());
+ }
+
+ return true;
+ }
Res = MCValue::get(&Sym, 0, 0);
return true;