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MC: Add TargetAsmBackend::WriteNopData and use to eliminate some target dependencies in MCMachOStreamer and MCAssembler.

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llvm-svn: 99248
This commit is contained in:
Daniel Dunbar 2010-03-23 02:36:58 +00:00
parent 1595ebfb4b
commit b33d212057
4 changed files with 80 additions and 64 deletions
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7
include/llvm/Target/TargetAsmBackend.h
View File

@ -102,6 +102,13 @@ public:
/// wider instruction.
virtual void RelaxInstruction(const MCInstFragment *IF,
MCInst &Res) const = 0;
/// WriteNopData - Write an (optimal) nop sequence of Count bytes to the given
/// output. If the target cannot generate such a sequence, it should return an
/// error.
///
/// \return - True on success.
virtual bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const = 0;
};
} // End llvm namespace

71
lib/MC/MCAssembler.cpp
View File

@ -373,66 +373,9 @@ void MCAssembler::LayoutSection(MCSectionData &SD,
SD.setFileSize(Address - SD.getAddress());
}
/// WriteNopData - Write optimal nops to the output file for the \arg Count
/// bytes. This returns the number of bytes written. It may return 0 if
/// the \arg Count is more than the maximum optimal nops.
///
/// FIXME this is X86 32-bit specific and should move to a better place.
static uint64_t WriteNopData(uint64_t Count, MCObjectWriter *OW) {
static const uint8_t Nops[16][16] = {
// nop
{0x90},
// xchg %ax,%ax
{0x66, 0x90},
// nopl (%[re]ax)
{0x0f, 0x1f, 0x00},
// nopl 0(%[re]ax)
{0x0f, 0x1f, 0x40, 0x00},
// nopl 0(%[re]ax,%[re]ax,1)
{0x0f, 0x1f, 0x44, 0x00, 0x00},
// nopw 0(%[re]ax,%[re]ax,1)
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
// nopl 0L(%[re]ax)
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
// nopl 0L(%[re]ax,%[re]ax,1)
{0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
// nopw 0L(%[re]ax,%[re]ax,1)
{0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
// nopw %cs:0L(%[re]ax,%[re]ax,1)
{0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
// nopl 0(%[re]ax,%[re]ax,1)
// nopw 0(%[re]ax,%[re]ax,1)
{0x0f, 0x1f, 0x44, 0x00, 0x00,
0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
// nopw 0(%[re]ax,%[re]ax,1)
// nopw 0(%[re]ax,%[re]ax,1)
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00,
0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
// nopw 0(%[re]ax,%[re]ax,1)
// nopl 0L(%[re]ax) */
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00,
0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
// nopl 0L(%[re]ax)
// nopl 0L(%[re]ax)
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00,
0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
// nopl 0L(%[re]ax)
// nopl 0L(%[re]ax,%[re]ax,1)
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00,
0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00}
};
if (Count > 15)
return 0;
for (uint64_t i = 0; i < Count; i++)
OW->Write8(uint8_t(Nops[Count - 1][i]));
return Count;
}
/// WriteFragmentData - Write the \arg F data to the output file.
static void WriteFragmentData(const MCFragment &F, MCObjectWriter *OW) {
static void WriteFragmentData(const MCAssembler &Asm, const MCFragment &F,
MCObjectWriter *OW) {
uint64_t Start = OW->getStream().tell();
(void) Start;
@ -456,11 +399,15 @@ static void WriteFragmentData(const MCFragment &F, MCObjectWriter *OW) {
// See if we are aligning with nops, and if so do that first to try to fill
// the Count bytes. Then if that did not fill any bytes or there are any
// bytes left to fill use the the Value and ValueSize to fill the rest.
// If we are aligning with nops, ask that target to emit the right data.
if (AF.getEmitNops()) {
uint64_t NopByteCount = WriteNopData(Count, OW);
Count -= NopByteCount;
if (!Asm.getBackend().WriteNopData(Count, OW))
llvm_report_error("unable to write nop sequence of " +
Twine(Count) + " bytes");
break;
}
// Otherwise, write out in multiples of the value size.
for (uint64_t i = 0; i != Count; ++i) {
switch (AF.getValueSize()) {
default:
@ -531,7 +478,7 @@ void MCAssembler::WriteSectionData(const MCSectionData *SD,
for (MCSectionData::const_iterator it = SD->begin(),
ie = SD->end(); it != ie; ++it)
WriteFragmentData(*it, OW);
WriteFragmentData(*this, *it, OW);
// Add section padding.
assert(SD->getFileSize() >= SD->getSize() && "Invalid section sizes!");

3
lib/MC/MCMachOStreamer.cpp
View File

@ -353,8 +353,7 @@ void MCMachOStreamer::EmitCodeAlignment(unsigned ByteAlignment,
unsigned MaxBytesToEmit) {
if (MaxBytesToEmit == 0)
MaxBytesToEmit = ByteAlignment;
// FIXME: The 0x90 is the default x86 1 byte nop opcode.
new MCAlignFragment(ByteAlignment, 0x90, 1, MaxBytesToEmit,
new MCAlignFragment(ByteAlignment, 0, 1, MaxBytesToEmit,
true /* EmitNops */, CurSectionData);
// Update the maximum alignment on the current section if necessary.

63
lib/Target/X86/X86AsmBackend.cpp
View File

@ -53,6 +53,8 @@ public:
}
void RelaxInstruction(const MCInstFragment *IF, MCInst &Res) const;
bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const;
};
static unsigned getRelaxedOpcode(unsigned Op) {
@ -98,6 +100,67 @@ void X86AsmBackend::RelaxInstruction(const MCInstFragment *IF,
Res.setOpcode(RelaxedOp);
}
/// WriteNopData - Write optimal nops to the output file for the \arg Count
/// bytes. This returns the number of bytes written. It may return 0 if
/// the \arg Count is more than the maximum optimal nops.
///
/// FIXME this is X86 32-bit specific and should move to a better place.
bool X86AsmBackend::WriteNopData(uint64_t Count, MCObjectWriter *OW) const {
static const uint8_t Nops[16][16] = {
// nop
{0x90},
// xchg %ax,%ax
{0x66, 0x90},
// nopl (%[re]ax)
{0x0f, 0x1f, 0x00},
// nopl 0(%[re]ax)
{0x0f, 0x1f, 0x40, 0x00},
// nopl 0(%[re]ax,%[re]ax,1)
{0x0f, 0x1f, 0x44, 0x00, 0x00},
// nopw 0(%[re]ax,%[re]ax,1)
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
// nopl 0L(%[re]ax)
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
// nopl 0L(%[re]ax,%[re]ax,1)
{0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
// nopw 0L(%[re]ax,%[re]ax,1)
{0x66, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
// nopw %cs:0L(%[re]ax,%[re]ax,1)
{0x66, 0x2e, 0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00},
// nopl 0(%[re]ax,%[re]ax,1)
// nopw 0(%[re]ax,%[re]ax,1)
{0x0f, 0x1f, 0x44, 0x00, 0x00,
0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
// nopw 0(%[re]ax,%[re]ax,1)
// nopw 0(%[re]ax,%[re]ax,1)
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00,
0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00},
// nopw 0(%[re]ax,%[re]ax,1)
// nopl 0L(%[re]ax) */
{0x66, 0x0f, 0x1f, 0x44, 0x00, 0x00,
0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
// nopl 0L(%[re]ax)
// nopl 0L(%[re]ax)
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00,
0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00},
// nopl 0L(%[re]ax)
// nopl 0L(%[re]ax,%[re]ax,1)
{0x0f, 0x1f, 0x80, 0x00, 0x00, 0x00, 0x00,
0x0f, 0x1f, 0x84, 0x00, 0x00, 0x00, 0x00, 0x00}
};
// Write an optimal sequence for the first 15 bytes.
uint64_t OptimalCount = (Count < 16) ? Count : 15;
for (uint64_t i = 0, e = OptimalCount; i != e; i++)
OW->Write8(Nops[OptimalCount - 1][i]);
// Finish with single byte nops.
for (uint64_t i = OptimalCount, e = Count; i != e; ++i)
OW->Write8(0x90);
return true;
}
/* *** */
class ELFX86AsmBackend : public X86AsmBackend {