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The BLX instruction is encoded differently than the BL, because why not? In

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particular, the immediate has 20-bits of value instead of 21. And bit 0 is '0'
always. Going through the BL fixup encoding was trashing the "bit 0 is '0'"
invariant.

Attempt to get the encoding at slightly more correct with this.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121336 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2010-12-09 00:39:08 +00:00
parent 8bce7cc3bf
commit 09aa3f0ef3
6 changed files with 54 additions and 19 deletions
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29
lib/Target/ARM/ARMAsmBackend.cpp
View File

@ -146,13 +146,33 @@ static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
// The value doesn't encode the low bit (always zero) and is offset by
// four. The value is encoded into disjoint bit positions in the destination
// opcode. x = unchanged, I = immediate value bit, S = sign extension bit
// xxxxxSIIIIIIIIII xxxxxIIIIIIIIIII
//
// BL: xxxxxSIIIIIIIIII xxxxxIIIIIIIIIII
//
// Note that the halfwords are stored high first, low second; so we need
// to transpose the fixup value here to map properly.
// FIXME: Something isn't quite right with this. Some, but not all, BLX
// instructions are getting the encoded value off by one.
unsigned isNeg = (int64_t(Value) < 0) ? 1 : 0;
uint32_t Binary = 0x3fffff & ((Value - 4) >> 1);
Binary = ((Binary & 0x7ff) << 16) | (Binary >> 11);
Binary = (Binary & 0x7ff) << 16; // Low imm11 value.
Binary |= (Binary & 0x1ffc00) >> 11; // High imm10 value.
Binary |= isNeg << 10; // Sign bit.
return Binary;
}
case ARM::fixup_arm_thumb_blx: {
// The value doesn't encode the low two bits (always zero) and is offset by
// four (see fixup_arm_thumb_cp). The value is encoded into disjoint bit
// positions in the destination opcode. x = unchanged, I = immediate value
// bit, S = sign extension bit, 0 = zero.
//
// BLX: xxxxxSIIIIIIIIII xxxxxIIIIIIIIII0
//
// Note that the halfwords are stored high first, low second; so we need
// to transpose the fixup value here to map properly.
unsigned isNeg = (int64_t(Value) < 0) ? 1 : 0;
uint32_t Binary = 0xfffff & ((Value - 2) >> 2);
Binary = (Binary & 0x3ff) << 17; // Low imm10L value.
Binary |= (Binary & 0xffc00) >> 10; // High imm10H value.
Binary |= isNeg << 10; // Sign bit.
return Binary;
}
case ARM::fixup_arm_thumb_cp:
@ -291,6 +311,7 @@ static unsigned getFixupKindNumBytes(unsigned Kind) {
case ARM::fixup_t2_branch:
case ARM::fixup_t2_pcrel_10:
case ARM::fixup_arm_thumb_bl:
case ARM::fixup_arm_thumb_blx:
return 4;
}
}

2
lib/Target/ARM/ARMCodeEmitter.cpp
View File

@ -173,6 +173,8 @@ namespace {
const { return 0; }
unsigned getThumbBLTargetOpValue(const MachineInstr &MI, unsigned Op)
const { return 0; }
unsigned getThumbBLXTargetOpValue(const MachineInstr &MI, unsigned Op)
const { return 0; }
unsigned getThumbBRTargetOpValue(const MachineInstr &MI, unsigned Op)
const { return 0; }
unsigned getBranchTargetOpValue(const MachineInstr &MI, unsigned Op)

5
lib/Target/ARM/ARMFixupKinds.h
View File

@ -35,9 +35,12 @@ enum Fixups {
// instructions.
fixup_t2_branch,
// fixup_arm_thumb_bl - Fixup for Thumb BL/BLX instructions.
// fixup_arm_thumb_blx - Fixup for Thumb BL instructions.
fixup_arm_thumb_bl,
// fixup_arm_thumb_blx - Fixup for Thumb BLX instructions.
fixup_arm_thumb_blx,
// fixup_arm_thumb_br - Fixup for Thumb branch instructions.
fixup_arm_thumb_br,

8
lib/Target/ARM/ARMInstrThumb.td
View File

@ -82,6 +82,10 @@ def t_bltarget : Operand<i32> {
let EncoderMethod = "getThumbBLTargetOpValue";
}
def t_blxtarget : Operand<i32> {
let EncoderMethod = "getThumbBLXTargetOpValue";
}
def MemModeThumbAsmOperand : AsmOperandClass {
let Name = "MemModeThumb";
let SuperClasses = [];
@ -395,7 +399,7 @@ let isCall = 1,
// ARMv5T and above, also used for Thumb2
def tBLXi : TIx2<0b11110, 0b11, 0,
(outs), (ins t_bltarget:$func, variable_ops), IIC_Br,
(outs), (ins t_blxtarget:$func, variable_ops), IIC_Br,
"blx\t$func",
[(ARMcall tglobaladdr:$func)]>,
Requires<[IsThumb, HasV5T, IsNotDarwin]> {
@ -448,7 +452,7 @@ let isCall = 1,
// ARMv5T and above, also used for Thumb2
def tBLXi_r9 : TIx2<0b11110, 0b11, 0,
(outs), (ins pred:$p, t_bltarget:$func, variable_ops),
(outs), (ins pred:$p, t_blxtarget:$func, variable_ops),
IIC_Br, "blx${p}\t$func",
[(ARMcall tglobaladdr:$func)]>,
Requires<[IsThumb, HasV5T, IsDarwin]> {

28
lib/Target/ARM/ARMMCCodeEmitter.cpp
View File

@ -53,6 +53,7 @@ public:
{ "fixup_arm_branch", 1, 24, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_t2_branch", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_bl", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_blx", 0, 32, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_br", 0, 16, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_thumb_cp", 1, 8, MCFixupKindInfo::FKF_IsPCRel },
{ "fixup_arm_movt_hi16", 0, 16, 0 },
@ -87,10 +88,15 @@ public:
SmallVectorImpl<MCFixup> &Fixups) const;
/// getThumbBLTargetOpValue - Return encoding info for Thumb immediate
/// branch target.
/// BL branch target.
uint32_t getThumbBLTargetOpValue(const MCInst &MI, unsigned OpIdx,
SmallVectorImpl<MCFixup> &Fixups) const;
/// getThumbBLXTargetOpValue - Return encoding info for Thumb immediate
/// BLX branch target.
uint32_t getThumbBLXTargetOpValue(const MCInst &MI, unsigned OpIdx,
SmallVectorImpl<MCFixup> &Fixups) const;
/// getThumbBRTargetOpValue - Return encoding info for Thumb branch target.
uint32_t getThumbBRTargetOpValue(const MCInst &MI, unsigned OpIdx,
SmallVectorImpl<MCFixup> &Fixups) const;
@ -443,6 +449,14 @@ getThumbBLTargetOpValue(const MCInst &MI, unsigned OpIdx,
return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_bl, Fixups);
}
/// getThumbBLXTargetOpValue - Return encoding info for Thumb immediate
/// BLX branch target.
uint32_t ARMMCCodeEmitter::
getThumbBLXTargetOpValue(const MCInst &MI, unsigned OpIdx,
SmallVectorImpl<MCFixup> &Fixups) const {
return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_blx, Fixups);
}
/// getThumbBRTargetOpValue - Return encoding info for Thumb branch target.
uint32_t ARMMCCodeEmitter::
getThumbBRTargetOpValue(const MCInst &MI, unsigned OpIdx,
@ -740,17 +754,7 @@ getAddrModeS1OpValue(const MCInst &MI, unsigned OpIdx,
uint32_t ARMMCCodeEmitter::
getAddrModePCOpValue(const MCInst &MI, unsigned OpIdx,
SmallVectorImpl<MCFixup> &Fixups) const {
const MCOperand &MO = MI.getOperand(OpIdx);
// If the destination is an immediate, we have nothing to do.
if (MO.isImm()) return MO.getImm();
assert (MO.isExpr() && "Unexpected branch target type!");
const MCExpr *Expr = MO.getExpr();
MCFixupKind Kind = MCFixupKind(ARM::fixup_arm_thumb_cp);
Fixups.push_back(MCFixup::Create(0, Expr, Kind));
// All of the information is in the fixup.
return 0;
return ::getBranchTargetOpValue(MI, OpIdx, ARM::fixup_arm_thumb_cp, Fixups);
}
/// getAddrMode5OpValue - Return encoding info for 'reg +/- imm10' operand.

1
utils/TableGen/EDEmitter.cpp
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@ -590,6 +590,7 @@ static int ARMFlagFromOpName(LiteralConstantEmitter *type,
MISC("t_brtarget", "kOperandTypeARMBranchTarget"); // ?
MISC("bltarget", "kOperandTypeARMBranchTarget"); // ?
MISC("t_bltarget", "kOperandTypeARMBranchTarget"); // ?
MISC("t_blxtarget", "kOperandTypeARMBranchTarget"); // ?
MISC("so_reg", "kOperandTypeARMSoReg"); // R, R, I
MISC("shift_so_reg", "kOperandTypeARMSoReg"); // R, R, I
MISC("t2_so_reg", "kOperandTypeThumb2SoReg"); // R, I