Fix roundtripping of Thumb BL/BLX instructions with immediate offsets instead of labels.
llvm-svn: 138874
diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
index 7cac54c..f6b8af8 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
@@ -465,11 +465,34 @@
return 0;
}
+// Thumb BL and BLX use a strange offset encoding where bits 22 and 21 are
+// determined by negating them and XOR'ing them with bit 23.
+static int32_t encodeThumbBLOffset(int32_t offset) {
+ offset >>= 1;
+ uint32_t S = (offset & 0x800000) >> 23;
+ uint32_t J1 = (offset & 0x400000) >> 22;
+ uint32_t J2 = (offset & 0x200000) >> 21;
+ J1 = (~J1 & 0x1);
+ J2 = (~J2 & 0x1);
+ J1 ^= S;
+ J2 ^= S;
+
+ offset &= ~0x600000;
+ offset |= J1 << 22;
+ offset |= J2 << 21;
+
+ return offset;
+}
+
/// getThumbBLTargetOpValue - Return encoding info for immediate branch target.
uint32_t ARMMCCodeEmitter::
getThumbBLTargetOpValue(const MCInst &MI, unsigned OpIdx,
SmallVectorImpl<MCFixup> &Fixups) const {
- return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_bl, Fixups);
+ const MCOperand MO = MI.getOperand(OpIdx);
+ if (MO.isExpr())
+ return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_bl,
+ Fixups);
+ return encodeThumbBLOffset(MO.getImm());
}
/// getThumbBLXTargetOpValue - Return encoding info for Thumb immediate
@@ -477,7 +500,11 @@
uint32_t ARMMCCodeEmitter::
getThumbBLXTargetOpValue(const MCInst &MI, unsigned OpIdx,
SmallVectorImpl<MCFixup> &Fixups) const {
- return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_blx, Fixups);
+ const MCOperand MO = MI.getOperand(OpIdx);
+ if (MO.isExpr())
+ return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_blx,
+ Fixups);
+ return encodeThumbBLOffset(MO.getImm());
}
/// getThumbBRTargetOpValue - Return encoding info for Thumb branch target.
@@ -486,7 +513,8 @@
SmallVectorImpl<MCFixup> &Fixups) const {
const MCOperand MO = MI.getOperand(OpIdx);
if (MO.isExpr())
- return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_br, Fixups);
+ return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_br,
+ Fixups);
return (MO.getImm() >> 1);
}