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[tablegen] Emit string literals instead of char arrays

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This changes the generated (Instr|Asm|Reg|Regclass)Name tables from this
form:
    extern const char HexagonInstrNameData[] = {
      /* 0 */ 'G', '_', 'F', 'L', 'O', 'G', '1', '0', 0,
      /* 9 */ 'E', 'N', 'D', 'L', 'O', 'O', 'P', '0', 0,
      /* 18 */ 'V', '6', '_', 'v', 'd', 'd', '0', 0,
      /* 26 */ 'P', 'S', '_', 'v', 'd', 'd', '0', 0,
      [...]
    };

...to this:

    extern const char HexagonInstrNameData[] = {
      /* 0 */ "G_FLOG10\0"
      /* 9 */ "ENDLOOP0\0"
      /* 18 */ "V6_vdd0\0"
      /* 26 */ "PS_vdd0\0"
      [...]
    };

This should make debugging and exploration a lot easier for mortals,
while providing a significant compile-time reduction for common compilers.

To avoid issues with low implementation limits, this is disabled by
default for visual studio.

To force output one way or the other, pass
`--long-string-literals=<bool>` to `tablegen`

Reviewers: mstorsjo, rnk

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D73044

A variation of this patch was originally committed in ce23515f5ab011 and
then reverted in e464b31c due to build failures.
This commit is contained in:
Luke Drummond 2020-01-15 14:14:01 +00:00
parent 6df1071106
commit a097bd08a1
6 changed files with 110 additions and 28 deletions
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8
cmake/modules/TableGen.cmake
View File

@ -58,6 +58,14 @@ function(tablegen project ofn)
endif()
endif()
# MSVC can't support long string literals ("long" > 65534 bytes)[1], so if there's
# a possibility of generated tables being consumed by MSVC, generate arrays of
# char literals, instead. If we're cross-compiling, then conservatively assume
# that the source might be consumed by MSVC.
# [1] https://docs.microsoft.com/en-us/cpp/cpp/compiler-limits?view=vs-2017
if (MSVC AND project STREQUAL LLVM)
list(APPEND LLVM_TABLEGEN_FLAGS "--long-string-literals=0")
endif()
if (CMAKE_GENERATOR MATCHES "Visual Studio")
# Visual Studio has problems with llvm-tblgen's native --write-if-changed
# behavior. Since it doesn't do restat optimizations anyway, just don't

9
utils/TableGen/AsmWriterEmitter.cpp
View File

@ -380,9 +380,7 @@ void AsmWriterEmitter::EmitPrintInstruction(raw_ostream &O) {
}
// Emit the string table itself.
O << " static const char AsmStrs[] = {\n";
StringTable.emit(O, printChar);
O << " };\n\n";
StringTable.emitStringLiteralDef(O, " static const char AsmStrs[]");
// Emit the lookup tables in pieces to minimize wasted bytes.
unsigned BytesNeeded = ((OpcodeInfoBits - BitsLeft) + 7) / 8;
@ -537,9 +535,8 @@ emitRegisterNameString(raw_ostream &O, StringRef AltName,
}
StringTable.layout();
O << " static const char AsmStrs" << AltName << "[] = {\n";
StringTable.emit(O, printChar);
O << " };\n\n";
StringTable.emitStringLiteralDef(O, Twine(" static const char AsmStrs") +
AltName + "[]");
O << " static const " << getMinimalTypeForRange(StringTable.size() - 1, 32)
<< " RegAsmOffset" << AltName << "[] = {";

5
utils/TableGen/InstrInfoEmitter.cpp
View File

@ -569,9 +569,8 @@ void InstrInfoEmitter::run(raw_ostream &OS) {
// Emit the array of instruction names.
InstrNames.layout();
OS << "extern const char " << TargetName << "InstrNameData[] = {\n";
InstrNames.emit(OS, printChar);
OS << "};\n\n";
InstrNames.emitStringLiteralDef(OS, Twine("extern const char ") + TargetName +
"InstrNameData[]");
OS << "extern const unsigned " << TargetName <<"InstrNameIndices[] = {";
Num = 0;

10
utils/TableGen/RegisterInfoEmitter.cpp
View File

@ -992,9 +992,8 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
// Emit the string table.
RegStrings.layout();
OS << "extern const char " << TargetName << "RegStrings[] = {\n";
RegStrings.emit(OS, printChar);
OS << "};\n\n";
RegStrings.emitStringLiteralDef(OS, Twine("extern const char ") + TargetName +
"RegStrings[]");
OS << "extern const MCRegisterDesc " << TargetName
<< "RegDesc[] = { // Descriptors\n";
@ -1065,9 +1064,8 @@ RegisterInfoEmitter::runMCDesc(raw_ostream &OS, CodeGenTarget &Target,
OS << "} // end anonymous namespace\n\n";
RegClassStrings.layout();
OS << "extern const char " << TargetName << "RegClassStrings[] = {\n";
RegClassStrings.emit(OS, printChar);
OS << "};\n\n";
RegClassStrings.emitStringLiteralDef(
OS, Twine("extern const char ") + TargetName + "RegClassStrings[]");
OS << "extern const MCRegisterClass " << TargetName
<< "MCRegisterClasses[] = {\n";

100
utils/TableGen/SequenceToOffsetTable.h
View File

@ -15,6 +15,7 @@
#ifndef LLVM_UTILS_TABLEGEN_SEQUENCETOOFFSETTABLE_H
#define LLVM_UTILS_TABLEGEN_SEQUENCETOOFFSETTABLE_H
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
@ -23,6 +24,61 @@
#include <map>
namespace llvm {
extern llvm::cl::opt<bool> EmitLongStrLiterals;
// Helper function for SequenceToOffsetTable<string>.
static inline void printStrLitEscChar(raw_ostream &OS, char C) {
const char *Escapes[] = {
"\\000", "\\001", "\\002", "\\003", "\\004", "\\005", "\\006", "\\007",
"\\010", "\\t", "\\n", "\\013", "\\014", "\\r", "\\016", "\\017",
"\\020", "\\021", "\\022", "\\023", "\\024", "\\025", "\\026", "\\027",
"\\030", "\\031", "\\032", "\\033", "\\034", "\\035", "\\036", "\\037",
" ", "!", "\\\"", "#", "$", "%", "&", "'",
"(", ")", "*", "+", ",", "-", ".", "/",
"0", "1", "2", "3", "4", "5", "6", "7",
"8", "9", ":", ";", "<", "=", ">", "?",
"@", "A", "B", "C", "D", "E", "F", "G",
"H", "I", "J", "K", "L", "M", "N", "O",
"P", "Q", "R", "S", "T", "U", "V", "W",
"X", "Y", "Z", "[", "\\\\", "]", "^", "_",
"`", "a", "b", "c", "d", "e", "f", "g",
"h", "i", "j", "k", "l", "m", "n", "o",
"p", "q", "r", "s", "t", "u", "v", "w",
"x", "y", "z", "{", "|", "}", "~", "\\177",
"\\200", "\\201", "\\202", "\\203", "\\204", "\\205", "\\206", "\\207",
"\\210", "\\211", "\\212", "\\213", "\\214", "\\215", "\\216", "\\217",
"\\220", "\\221", "\\222", "\\223", "\\224", "\\225", "\\226", "\\227",
"\\230", "\\231", "\\232", "\\233", "\\234", "\\235", "\\236", "\\237",
"\\240", "\\241", "\\242", "\\243", "\\244", "\\245", "\\246", "\\247",
"\\250", "\\251", "\\252", "\\253", "\\254", "\\255", "\\256", "\\257",
"\\260", "\\261", "\\262", "\\263", "\\264", "\\265", "\\266", "\\267",
"\\270", "\\271", "\\272", "\\273", "\\274", "\\275", "\\276", "\\277",
"\\300", "\\301", "\\302", "\\303", "\\304", "\\305", "\\306", "\\307",
"\\310", "\\311", "\\312", "\\313", "\\314", "\\315", "\\316", "\\317",
"\\320", "\\321", "\\322", "\\323", "\\324", "\\325", "\\326", "\\327",
"\\330", "\\331", "\\332", "\\333", "\\334", "\\335", "\\336", "\\337",
"\\340", "\\341", "\\342", "\\343", "\\344", "\\345", "\\346", "\\347",
"\\350", "\\351", "\\352", "\\353", "\\354", "\\355", "\\356", "\\357",
"\\360", "\\361", "\\362", "\\363", "\\364", "\\365", "\\366", "\\367",
"\\370", "\\371", "\\372", "\\373", "\\374", "\\375", "\\376", "\\377"};
static_assert(sizeof Escapes / sizeof Escapes[0] ==
std::numeric_limits<unsigned char>::max() + 1,
"unsupported character type");
OS << Escapes[static_cast<unsigned char>(C)];
}
static inline void printChar(raw_ostream &OS, char C) {
unsigned char UC(C);
if (isalnum(UC) || ispunct(UC)) {
OS << '\'';
if (C == '\\' || C == '\'')
OS << '\\';
OS << C << '\'';
} else {
OS << unsigned(UC);
}
}
/// SequenceToOffsetTable - Collect a number of terminated sequences of T.
/// Compute the layout of a table that contains all the sequences, possibly by
@ -108,6 +164,37 @@ public:
return I->second + (I->first.size() - Seq.size());
}
/// `emitStringLiteralDef` - Print out the table as the body of an array
/// initializer, where each element is a C string literal terminated by
/// `\0`. Falls back to emitting a comma-separated integer list if
/// `EmitLongStrLiterals` is false
void emitStringLiteralDef(raw_ostream &OS, const llvm::Twine &Decl) const {
assert(Entries && "Call layout() before emitStringLiteralDef()");
if (EmitLongStrLiterals) {
OS << "\n#ifdef __GNUC__\n"
<< "#pragma GCC diagnostic push\n"
<< "#pragma GCC diagnostic ignored \"-Woverlength-strings\"\n"
<< "#endif\n"
<< Decl << " = {\n";
} else {
OS << Decl << " = {\n";
emit(OS, printChar, "0");
OS << "\n};\n\n";
return;
}
for (auto I : Seqs) {
OS << " /* " << I.second << " */ \"";
for (auto C : I.first) {
printStrLitEscChar(OS, C);
}
OS << "\\0\"\n";
}
OS << "};\n"
<< "#ifdef __GNUC__\n"
<< "#pragma GCC diagnostic pop\n"
<< "#endif\n\n";
}
/// emit - Print out the table as the body of an array initializer.
/// Use the Print function to print elements.
void emit(raw_ostream &OS,
@ -127,19 +214,6 @@ public:
}
};
// Helper function for SequenceToOffsetTable<string>.
static inline void printChar(raw_ostream &OS, char C) {
unsigned char UC(C);
if (isalnum(UC) || ispunct(UC)) {
OS << '\'';
if (C == '\\' || C == '\'')
OS << '\\';
OS << C << '\'';
} else {
OS << unsigned(UC);
}
}
} // end namespace llvm
#endif

6
utils/TableGen/TableGen.cpp
View File

@ -60,6 +60,12 @@ namespace llvm {
/// Storage for TimeRegionsOpt as a global so that backends aren't required to
/// include CommandLine.h
bool TimeRegions = false;
cl::opt<bool> EmitLongStrLiterals(
"long-string-literals",
cl::desc("when emitting large string tables, prefer string literals over "
"comma-separated char literals. This can be a readability and "
"compile-time performance win, but upsets some compilers"),
cl::Hidden, cl::init(true));
} // end namespace llvm
namespace {