[AVX] Make Inits Foldable

Manage Inits in a FoldingSet.  This provides several benefits:

- Memory for Inits is properly managed

- Duplicate Inits are folded into Flyweights, saving memory

- It enforces const-correctness, protecting against certain classes
  of bugs

The above benefits allow Inits to be used in more contexts, which in
turn provides more dynamism to TableGen.  This enhanced capability
will be used by the AVX code generator to a fold common patterns
together.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134907 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 11 insertions, 10 deletions

diff --git a/utils/TableGen/ARMDecoderEmitter.cpp b/utils/TableGen/ARMDecoderEmitter.cpp
index 8a5dc8b..3721ed4 100644
--- a/utils/TableGen/ARMDecoderEmitter.cpp
+++ b/utils/TableGen/ARMDecoderEmitter.cpp
@@ -114,7 +114,7 @@ enum {
 
 /// byteFromBitsInit - Return the byte value from a BitsInit.
 /// Called from getByteField().
-static uint8_t byteFromBitsInit(BitsInit &init) {
+static uint8_t byteFromBitsInit(const BitsInit &init) {
   int width = init.getNumBits();
 
   assert(width <= 8 && "Field is too large for uint8_t!");
@@ -125,7 +125,7 @@ static uint8_t byteFromBitsInit(BitsInit &init) {
   uint8_t ret = 0;
 
   for (index = 0; index < width; index++) {
-    if (static_cast<BitInit*>(init.getBit(index))->getValue())
+    if (static_cast<const BitInit*>(init.getBit(index))->getValue())
       ret |= mask;
 
     mask <<= 1;
@@ -135,12 +135,12 @@ static uint8_t byteFromBitsInit(BitsInit &init) {
 }
 
 static uint8_t getByteField(const Record &def, const char *str) {
-  BitsInit *bits = def.getValueAsBitsInit(str);
+  const BitsInit *bits = def.getValueAsBitsInit(str);
   return byteFromBitsInit(*bits);
 }
 
-static BitsInit &getBitsField(const Record &def, const char *str) {
-  BitsInit *bits = def.getValueAsBitsInit(str);
+static const BitsInit &getBitsField(const Record &def, const char *str) {
+  const BitsInit *bits = def.getValueAsBitsInit(str);
   return *bits;
 }
 
@@ -183,15 +183,15 @@ static bool ValueNotSet(bit_value_t V) {
 static int Value(bit_value_t V) {
   return ValueNotSet(V) ? -1 : (V == BIT_FALSE ? 0 : 1);
 }
-static bit_value_t bitFromBits(BitsInit &bits, unsigned index) {
-  if (BitInit *bit = dynamic_cast<BitInit*>(bits.getBit(index)))
+static bit_value_t bitFromBits(const BitsInit &bits, unsigned index) {
+  if (const BitInit *bit = dynamic_cast<const BitInit*>(bits.getBit(index)))
     return bit->getValue() ? BIT_TRUE : BIT_FALSE;
 
   // The bit is uninitialized.
   return BIT_UNSET;
 }
 // Prints the bit value for each position.
-static void dumpBits(raw_ostream &o, BitsInit &bits) {
+static void dumpBits(raw_ostream &o, const BitsInit &bits) {
   unsigned index;
 
   for (index = bits.getNumBits(); index > 0; index--) {
@@ -424,7 +424,8 @@ protected:
     if (AllInstructions[Opcode]->isPseudo)
       return;
 
-    BitsInit &Bits = getBitsField(*AllInstructions[Opcode]->TheDef, "Inst");
+    const BitsInit &Bits = getBitsField(*AllInstructions[Opcode]->TheDef,
+                                        "Inst");
 
     for (unsigned i = 0; i < BIT_WIDTH; ++i)
       Insn[i] = bitFromBits(Bits, i);
@@ -1558,7 +1559,7 @@ ARMDEBackend::populateInstruction(const CodeGenInstruction &CGI,
   const StringRef Name = Def.getName();
   uint8_t Form = getByteField(Def, "Form");
 
-  BitsInit &Bits = getBitsField(Def, "Inst");
+  const BitsInit &Bits = getBitsField(Def, "Inst");
 
   // If all the bit positions are not specified; do not decode this instruction.
   // We are bound to fail!  For proper disassembly, the well-known encoding bits