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llvm-mc: Symbols in a relocatable expression of the (a - b + cst) form are

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allowed to be undefined when the expression is seen, we cannot enforce the
same-section requirement until the entire assembly file has been seen.

llvm-svn: 74565
This commit is contained in:
Daniel Dunbar 2009-06-30 22:49:27 +00:00
parent c0fb316bd3
commit d0589c59b3
3 changed files with 14 additions and 9 deletions
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7
include/llvm/MC/MCValue.h
View File

@ -26,7 +26,8 @@ class MCSymbol;
/// relocations of this general form, but we need to represent this anyway.
///
/// In the general form, SymbolB can only be defined if SymbolA is, and both
/// must be in the same (non-external) section.
/// must be in the same (non-external) section. The latter constraint is not
/// enforced, since a symbol's section may not be known at construction.
///
/// Note that this class must remain a simple POD value class, because we need
/// it to live in unions etc.
@ -52,9 +53,7 @@ public:
static MCValue get(MCSymbol *SymA, MCSymbol *SymB = 0, int64_t Val = 0) {
MCValue R;
assert((!SymB || (SymA && SymA->getSection() &&
SymA->getSection() == SymB->getSection())) &&
"Invalid relocatable MCValue!");
assert((!SymB || SymA) && "Invalid relocatable MCValue!");
R.Cst = Val;
R.SymA = SymA;
R.SymB = SymB;

7
test/MC/AsmParser/exprs.s
View File

@ -52,4 +52,11 @@ k:
i = (j + 10) - (k + 2)
.long i
l = m - n + 4
.text
m:
n:
nop

9
tools/llvm-mc/AsmExpr.cpp
View File

@ -37,12 +37,11 @@ static bool EvaluateSymbolicAdd(const MCValue &LHS, MCSymbol *RHS_A,
MCSymbol *A = LHS.getSymA() ? LHS.getSymA() : RHS_A;
MCSymbol *B = LHS.getSymB() ? LHS.getSymB() : RHS_B;
if (B) {
// If we have a negated symbol, then we must have also have a
// non-negated symbol, and both symbols must be in the same
// non-external section. We can do this check later to permit
// expressions which eventually fold to a representable form -- such
// If we have a negated symbol, then we must have also have a non-negated
// symbol in order to encode the expression. We can do this check later to
// permit expressions which eventually fold to a representable form -- such
// as (a + (0 - b)) -- if necessary.
if (!A || !A->getSection() || A->getSection() != B->getSection())
if (!A)
return false;
}
Res = MCValue::get(A, B, LHS.getConstant() + RHS_Cst);