Commit 5d57578a authored by Leonard Grey's avatar Leonard Grey Committed by Nico Weber
Browse files

[MC] Recursively calculate symbol offset 

This is speculative since I'm not sure if there's some implicit contract that a
variable symbol must not have another variable symbol in its evaluation tree.

Downstream bug: https://bugs.chromium.org/p/chromium/issues/detail?id=471146#c23.

Test is based on alias.s (removed checks since we just need to know it didn't
crash).

Differential Revision: https://reviews.llvm.org/D109109
parent 14127190

llvm/lib/MC/MCFragment.cpp

+6 −2
Original line number Diff line number Diff line
@@ -128,7 +128,11 @@ static bool getSymbolOffsetImpl(const MCAsmLayout &Layout, const MCSymbol &S, 
  const MCSymbolRefExpr *A = Target.getSymA();

  if (A) {

    uint64_t ValA;

    if (!getLabelOffset(Layout, A->getSymbol(), ReportError, ValA))

    // FIXME: On most platforms, `Target`'s component symbols are labels from

    // having been simplified during evaluation, but on Mach-O they can be

    // variables due to PR19203. This, and the line below for `B` can be

    // restored to call `getLabelOffset` when PR19203 is fixed.

    if (!getSymbolOffsetImpl(Layout, A->getSymbol(), ReportError, ValA))

      return false;

    Offset += ValA;

  }
@@ -136,7 +140,7 @@ static bool getSymbolOffsetImpl(const MCAsmLayout &Layout, const MCSymbol &S, 
  const MCSymbolRefExpr *B = Target.getSymB();

  if (B) {

    uint64_t ValB;

    if (!getLabelOffset(Layout, B->getSymbol(), ReportError, ValB))

    if (!getSymbolOffsetImpl(Layout, B->getSymbol(), ReportError, ValB))

      return false;

    Offset -= ValB;

  }

llvm/test/MC/MachO/chained-alias-offset.s

0 → 100644
+12 −0
Original line number Diff line number Diff line 
// RUN: llvm-mc -triple x86_64-apple-macos %s -filetype=obj | llvm-readobj --symbols - | FileCheck %s

l_a:

l_b = l_a + 1

l_c = l_b

        .long l_c



// CHECK: Name: l_a

// CHECK: Value: 0x0

// CHECK: Name: l_b

// CHECK: Value: 0x1

// CHECK: Name: l_c

// CHECK: Value: 0x1