ARM: diagnose invalid local fixups on Thumb1
We previously stopped producing Thumb2 relaxations when they weren't supported,
but only diagnosed the case where an actual relocation was produced. We should
also tell people if local symbols aren't going to work rather than silently
overflowing.
llvm-svn: 249164
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
index 1fe2dbe..75d3321 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
@@ -181,9 +181,8 @@
return false;
}
-bool ARMAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
- const MCRelaxableFragment *DF,
- const MCAsmLayout &Layout) const {
+const char *ARMAsmBackend::reasonForFixupRelaxation(const MCFixup &Fixup,
+ uint64_t Value) const {
switch ((unsigned)Fixup.getKind()) {
case ARM::fixup_arm_thumb_br: {
// Relaxing tB to t2B. tB has a signed 12-bit displacement with the
@@ -193,7 +192,9 @@
//
// Relax if the value is too big for a (signed) i8.
int64_t Offset = int64_t(Value) - 4;
- return Offset > 2046 || Offset < -2048;
+ if (Offset > 2046 || Offset < -2048)
+ return "out of range pc-relative fixup value";
+ break;
}
case ARM::fixup_arm_thumb_bcc: {
// Relaxing tBcc to t2Bcc. tBcc has a signed 9-bit displacement with the
@@ -203,23 +204,40 @@
//
// Relax if the value is too big for a (signed) i8.
int64_t Offset = int64_t(Value) - 4;
- return Offset > 254 || Offset < -256;
+ if (Offset > 254 || Offset < -256)
+ return "out of range pc-relative fixup value";
+ break;
}
case ARM::fixup_thumb_adr_pcrel_10:
case ARM::fixup_arm_thumb_cp: {
// If the immediate is negative, greater than 1020, or not a multiple
// of four, the wide version of the instruction must be used.
int64_t Offset = int64_t(Value) - 4;
- return Offset > 1020 || Offset < 0 || Offset & 3;
+ if (Offset & 3)
+ return "misaligned pc-relative fixup value";
+ else if (Offset > 1020 || Offset < 0)
+ return "out of range pc-relative fixup value";
+ break;
}
- case ARM::fixup_arm_thumb_cb:
+ case ARM::fixup_arm_thumb_cb: {
// If we have a Thumb CBZ or CBNZ instruction and its target is the next
// instruction it is is actually out of range for the instruction.
// It will be changed to a NOP.
int64_t Offset = (Value & ~1);
- return Offset == 2;
+ if (Offset == 2)
+ return "will be converted to nop";
+ break;
}
- llvm_unreachable("Unexpected fixup kind in fixupNeedsRelaxation()!");
+ default:
+ llvm_unreachable("Unexpected fixup kind in reasonForFixupRelaxation()!");
+ }
+ return nullptr;
+}
+
+bool ARMAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value,
+ const MCRelaxableFragment *DF,
+ const MCAsmLayout &Layout) const {
+ return reasonForFixupRelaxation(Fixup, Value);
}
void ARMAsmBackend::relaxInstruction(const MCInst &Inst, MCInst &Res) const {
@@ -318,9 +336,10 @@
return Value;
}
-static unsigned adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
- bool IsPCRel, MCContext *Ctx,
- bool IsLittleEndian) {
+unsigned ARMAsmBackend::adjustFixupValue(const MCFixup &Fixup, uint64_t Value,
+ bool IsPCRel, MCContext *Ctx,
+ bool IsLittleEndian,
+ bool IsResolved) const {
unsigned Kind = Fixup.getKind();
switch (Kind) {
default:
@@ -384,8 +403,6 @@
return Value;
}
- case ARM::fixup_thumb_adr_pcrel_10:
- return ((Value - 4) >> 2) & 0xff;
case ARM::fixup_arm_adr_pcrel_12: {
// ARM PC-relative values are offset by 8.
Value -= 8;
@@ -518,21 +535,38 @@
((uint16_t)imm10LBits) << 1);
return joinHalfWords(FirstHalf, SecondHalf, IsLittleEndian);
}
+ case ARM::fixup_thumb_adr_pcrel_10:
case ARM::fixup_arm_thumb_cp:
- // Offset by 4, and don't encode the low two bits. Two bytes of that
- // 'off by 4' is implicitly handled by the half-word ordering of the
- // Thumb encoding, so we only need to adjust by 2 here.
- return ((Value - 2) >> 2) & 0xff;
+ // On CPUs supporting Thumb2, this will be relaxed to an ldr.w, otherwise we
+ // could have an error on our hands.
+ if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2] && IsResolved) {
+ const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
+ if (FixupDiagnostic)
+ Ctx->reportFatalError(Fixup.getLoc(), FixupDiagnostic);
+ }
+ // Offset by 4, and don't encode the low two bits.
+ return ((Value - 4) >> 2) & 0xff;
case ARM::fixup_arm_thumb_cb: {
// Offset by 4 and don't encode the lower bit, which is always 0.
+ // FIXME: diagnose if no Thumb2
uint32_t Binary = (Value - 4) >> 1;
return ((Binary & 0x20) << 4) | ((Binary & 0x1f) << 3);
}
case ARM::fixup_arm_thumb_br:
// Offset by 4 and don't encode the lower bit, which is always 0.
+ if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2]) {
+ const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
+ if (FixupDiagnostic)
+ Ctx->reportFatalError(Fixup.getLoc(), FixupDiagnostic);
+ }
return ((Value - 4) >> 1) & 0x7ff;
case ARM::fixup_arm_thumb_bcc:
// Offset by 4 and don't encode the lower bit, which is always 0.
+ if (Ctx && !STI->getFeatureBits()[ARM::FeatureThumb2]) {
+ const char *FixupDiagnostic = reasonForFixupRelaxation(Fixup, Value);
+ if (FixupDiagnostic)
+ Ctx->reportFatalError(Fixup.getLoc(), FixupDiagnostic);
+ }
return ((Value - 4) >> 1) & 0xff;
case ARM::fixup_arm_pcrel_10_unscaled: {
Value = Value - 8; // ARM fixups offset by an additional word and don't
@@ -617,7 +651,7 @@
// the instruction. This allows adjustFixupValue() to issue a diagnostic
// if the value aren't invalid.
(void)adjustFixupValue(Fixup, Value, false, &Asm.getContext(),
- IsLittleEndian);
+ IsLittleEndian, IsResolved);
}
/// getFixupKindNumBytes - The number of bytes the fixup may change.
@@ -720,7 +754,8 @@
unsigned DataSize, uint64_t Value,
bool IsPCRel) const {
unsigned NumBytes = getFixupKindNumBytes(Fixup.getKind());
- Value = adjustFixupValue(Fixup, Value, IsPCRel, nullptr, IsLittleEndian);
+ Value =
+ adjustFixupValue(Fixup, Value, IsPCRel, nullptr, IsLittleEndian, true);
if (!Value)
return; // Doesn't change encoding.