ARM BL/BLX instruction fixups should use relocations.
We on the linker to resolve calls to the appropriate BL/BLX instruction
to make interworking function correctly. It uses the symbol in the
relocation to do that, so we need to be careful about being too clever.
To enable this for ARM mode, split the BL/BLX fixup kind off from the
unconditional-branch fixups.
rdar://10927209
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151571 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp b/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
index 55ea023..d3a3d3a 100644
--- a/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
@@ -78,6 +78,8 @@
{ "fixup_t2_condbranch", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_t2_uncondbranch", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_br", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
+{ "fixup_arm_bl", 0, 24, MCFixupKindInfo::FKF_IsPCRel },
+{ "fixup_arm_blx", 0, 24, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_bl", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_blx", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_cb", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
@@ -106,18 +108,28 @@
/// if necessary.
void processFixupValue(const MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFixup &Fixup, const MCFragment *DF,
- MCValue &Target, uint64_t &Value) {
+ MCValue &Target, uint64_t &Value,
+ bool &IsResolved) {
+ const MCSymbolRefExpr *A = Target.getSymA();
// Some fixups to thumb function symbols need the low bit (thumb bit)
// twiddled.
if ((unsigned)Fixup.getKind() != ARM::fixup_arm_ldst_pcrel_12 &&
(unsigned)Fixup.getKind() != ARM::fixup_t2_ldst_pcrel_12 &&
(unsigned)Fixup.getKind() != ARM::fixup_arm_thumb_cp) {
- if (const MCSymbolRefExpr *A = Target.getSymA()) {
+ if (A) {
const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
if (Asm.isThumbFunc(&Sym))
Value |= 1;
}
}
+ // We must always generate a relocation for BL/BLX instructions if we have
+ // a symbol to reference, as the linker relies on knowing the destination
+ // symbol's thumb-ness to get interworking right.
+ if (A && ((unsigned)Fixup.getKind() == ARM::fixup_arm_thumb_blx ||
+ (unsigned)Fixup.getKind() == ARM::fixup_arm_thumb_bl ||
+ (unsigned)Fixup.getKind() == ARM::fixup_arm_blx ||
+ (unsigned)Fixup.getKind() == ARM::fixup_arm_bl))
+ IsResolved = false;
}
bool mayNeedRelaxation(const MCInst &Inst) const;
@@ -343,6 +355,8 @@
case ARM::fixup_arm_condbranch:
case ARM::fixup_arm_uncondbranch:
+ case ARM::fixup_arm_bl:
+ case ARM::fixup_arm_blx:
// These values don't encode the low two bits since they're always zero.
// Offset by 8 just as above.
return 0xffffff & ((Value - 8) >> 2);
@@ -552,6 +566,8 @@
case ARM::fixup_arm_ldst_pcrel_12:
case ARM::fixup_arm_pcrel_10:
case ARM::fixup_arm_adr_pcrel_12:
+ case ARM::fixup_arm_bl:
+ case ARM::fixup_arm_blx:
case ARM::fixup_arm_condbranch:
case ARM::fixup_arm_uncondbranch:
return 3;