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[TableGen] Allow asm writer to use up to 3 OpInfo tables instead of 2. This allows x86 to use 56 total bits made up of a 32-bit, 16-bit, and 8-bit table. Previously we were using 64 total bits. 

This saves 14K from the x86 table size. And saves space on other targets as well.

llvm-svn: 257315
This commit is contained in:
Craig Topper 2016-01-11 05:13:41 +00:00
parent 1ab390957c
commit 14d917302f
1 changed files with 36 additions and 34 deletions
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70
llvm/utils/TableGen/AsmWriterEmitter.cpp
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@ -390,47 +390,49 @@ void AsmWriterEmitter::EmitPrintInstruction(raw_ostream &O) {
TableDrivenOperandPrinters.push_back(std::move(UniqueOperandCommands));
}
// We always emit at least one 32-bit table. A second table is emitted if
// more bits are needed.
O<<" static const uint32_t OpInfo[] = {\n";
for (unsigned i = 0, e = NumberedInstructions->size(); i != e; ++i) {
O << " " << (OpcodeInfo[i] & 0xffffffff) << "U,\t// "
<< NumberedInstructions->at(i)->TheDef->getName() << "\n";
}
O << " };\n\n";
if (BitsLeft < 32) {
// Add a second OpInfo table only when it is necessary.
// Adjust the type of the second table based on the number of bits needed.
O << " static const uint"
<< ((BitsLeft < 16) ? "32" : (BitsLeft < 24) ? "16" : "8")
<< "_t OpInfo2[] = {\n";
for (unsigned i = 0, e = NumberedInstructions->size(); i != e; ++i) {
O << " " << (OpcodeInfo[i] >> 32) << "U,\t// "
<< NumberedInstructions->at(i)->TheDef->getName() << "\n";
}
O << " };\n\n";
}
// Emit the string itself.
// Emit the string table itself.
O << " static const char AsmStrs[] = {\n";
StringTable.emit(O, printChar);
O << " };\n\n";
// Emit the lookup tables in pieces to minimize wasted bytes.
unsigned BytesNeeded = ((64 - BitsLeft) + 7) / 8;
unsigned Table = 0, Shift = 0;
SmallString<128> BitsString;
raw_svector_ostream BitsOS(BitsString);
// If the total bits is more than 32-bits we need to use a 64-bit type.
BitsOS << " uint" << ((BitsLeft < 32) ? 64 : 32) << "_t Bits = 0;\n";
while (BytesNeeded != 0) {
// Figure out how big this table section needs to be, but no bigger than 4.
unsigned TableSize = std::min(1 << Log2_32(BytesNeeded), 4);
BytesNeeded -= TableSize;
TableSize *= 8; // Convert to bits;
uint64_t Mask = (1ULL << TableSize) - 1;
O << " static const uint" << TableSize << "_t OpInfo" << Table
<< "[] = {\n";
for (unsigned i = 0, e = NumberedInstructions->size(); i != e; ++i) {
O << " " << ((OpcodeInfo[i] >> Shift) & Mask) << "U,\t// "
<< NumberedInstructions->at(i)->TheDef->getName() << "\n";
}
O << " };\n\n";
// Emit string to combine the individual table lookups.
BitsOS << " Bits |= ";
// If the total bits is more than 32-bits we need to use a 64-bit type.
if (BitsLeft < 32)
BitsOS << "(uint64_t)";
BitsOS << "OpInfo" << Table << "[MI->getOpcode()] << " << Shift << ";\n";
// Prepare the shift for the next iteration and increment the table count.
Shift += TableSize;
++Table;
}
// Emit the initial tab character.
O << " O << \"\\t\";\n\n";
O << " // Emit the opcode for the instruction.\n";
if (BitsLeft < 32) {
// If we have two tables then we need to perform two lookups and combine
// the results into a single 64-bit value.
O << " uint64_t Bits1 = OpInfo[MI->getOpcode()];\n"
<< " uint64_t Bits2 = OpInfo2[MI->getOpcode()];\n"
<< " uint64_t Bits = (Bits2 << 32) | Bits1;\n";
} else {
// If only one table is used we just need to perform a single lookup.
O << " uint32_t Bits = OpInfo[MI->getOpcode()];\n";
}
O << BitsString;
// Emit the starting string.
O << " assert(Bits != 0 && \"Cannot print this instruction.\");\n"
<< " O << AsmStrs+(Bits & " << (1 << AsmStrBits)-1 << ")-1;\n\n";