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llvm-svn: 298792
This commit is contained in:
Rui Ueyama
2017-03-26 03:20:30 +00:00
parent 0d256c0f5d
commit 760197cef1
1 changed files with 19 additions and 9 deletions
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28
lld/ELF/Relocations.cpp
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@@ -312,6 +312,15 @@ static bool isRelExpr(RelExpr Expr) {
R_PAGE_PC, R_RELAX_GOT_PC>(Expr);
}
// Returns true if a given relocation can be computed at link-time.
//
// For instance, we know the offset from a relocation to its target at
// link-time if the relocation is PC-relative and refers a
// (non-interruptible) function in the same executable. This function
// will return true for such relocation.
//
// If this function returns false, that means we need to emit a
// dynamic relocation so that the relocation will be fixed at load-time.
template <class ELFT>
static bool
isStaticLinkTimeConstant(RelExpr E, uint32_t Type, const SymbolBody &Body,
@@ -331,16 +340,19 @@ isStaticLinkTimeConstant(RelExpr E, uint32_t Type, const SymbolBody &Body,
if (isPreemptible(Body, Type))
return false;
if (!Config->Pic)
return true;
// For the target and the relocation, we want to know if they are
// absolute or relative.
bool AbsVal = isAbsoluteValue<ELFT>(Body);
bool RelE = isRelExpr(E);
if (AbsVal && !RelE)
return true;
if (!AbsVal && RelE)
return true;
if (!AbsVal && !RelE)
return Target->usesOnlyLowPageBits(Type);
// Relative relocation to an absolute value. This is normally unrepresentable,
// but if the relocation refers to a weak undefined symbol, we allow it to
@@ -350,16 +362,14 @@ isStaticLinkTimeConstant(RelExpr E, uint32_t Type, const SymbolBody &Body,
// Another special case is MIPS _gp_disp symbol which represents offset
// between start of a function and '_gp' value and defined as absolute just
// to simplify the code.
if (AbsVal && RelE) {
if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak())
return true;
error(S.getLocation<ELFT>(RelOff) + ": relocation " + toString(Type) +
" cannot refer to absolute symbol '" + toString(Body) +
"' defined in " + toString(Body.File));
assert(AbsVal && RelE);
if (Body.isUndefined() && !Body.isLocal() && Body.symbol()->isWeak())
return true;
}
return Target->usesOnlyLowPageBits(Type);
error(S.getLocation<ELFT>(RelOff) + ": relocation " + toString(Type) +
" cannot refer to absolute symbol '" + toString(Body) +
"' defined in " + toString(Body.File));
return true;
}
static RelExpr toPlt(RelExpr Expr) {