Rearrange handling of jump tables. Highlights:

1. MachineJumpTableInfo is now created lazily for a function the first time
   it actually makes a jump table instead of for every function.
2. The encoding of jump table entries is now described by the
   MachineJumpTableInfo::JTEntryKind enum.  This enum is determined by the
   TLI::getJumpTableEncoding() hook, instead of by lots of code scattered
   throughout the compiler that "knows" that jump table entries are always
   32-bits in pic mode (for example).
3. The size and alignment of jump table entries is now calculated based on
   their kind, instead of at machinefunction creation time.

Future work includes using the EntryKind in more places in the compiler,
eliminating other logic that "knows" the layout of jump tables in various
situations.

llvm-svn: 94470

1 files changed, 22 insertions, 16 deletions

diff --git a/llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp b/llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp
index 4dc119dddb8..080a88cc561 100644
--- a/llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp
+++ b/llvm/lib/ExecutionEngine/JIT/JITEmitter.cpp
@@ -847,9 +847,7 @@ static unsigned GetJumpTableSizeInBytes(MachineJumpTableInfo *MJTI) {
   for (unsigned i = 0, e = JT.size(); i != e; ++i)
     NumEntries += JT[i].MBBs.size();
 
-  unsigned EntrySize = MJTI->getEntrySize();
-
-  return NumEntries * EntrySize;
+  return NumEntries * MJTI->getEntrySize(*TheJIT->getTargetData());
 }
 
 static uintptr_t RoundUpToAlign(uintptr_t Size, unsigned Alignment) {
@@ -1017,7 +1015,6 @@ void JITEmitter::startFunction(MachineFunction &F) {
   if (MemMgr->NeedsExactSize()) {
     DEBUG(dbgs() << "JIT: ExactSize\n");
     const TargetInstrInfo* TII = F.getTarget().getInstrInfo();
-    MachineJumpTableInfo *MJTI = F.getJumpTableInfo();
     MachineConstantPool *MCP = F.getConstantPool();
 
     // Ensure the constant pool/jump table info is at least 4-byte aligned.
@@ -1029,11 +1026,14 @@ void JITEmitter::startFunction(MachineFunction &F) {
     // Add the constant pool size
     ActualSize += GetConstantPoolSizeInBytes(MCP, TheJIT->getTargetData());
 
-    // Add the aligment of the jump table info
-    ActualSize = RoundUpToAlign(ActualSize, MJTI->getAlignment());
+    if (MachineJumpTableInfo *MJTI = F.getJumpTableInfo()) {
+      // Add the aligment of the jump table info
+      ActualSize = RoundUpToAlign(ActualSize,
+                             MJTI->getEntryAlignment(*TheJIT->getTargetData()));
 
-    // Add the jump table size
-    ActualSize += GetJumpTableSizeInBytes(MJTI);
+      // Add the jump table size
+      ActualSize += GetJumpTableSizeInBytes(MJTI);
+    }
 
     // Add the alignment for the function
     ActualSize = RoundUpToAlign(ActualSize,
@@ -1062,7 +1062,8 @@ void JITEmitter::startFunction(MachineFunction &F) {
   emitAlignment(16);
 
   emitConstantPool(F.getConstantPool());
-  initJumpTableInfo(F.getJumpTableInfo());
+  if (MachineJumpTableInfo *MJTI = F.getJumpTableInfo())
+    initJumpTableInfo(MJTI);
 
   // About to start emitting the machine code for the function.
   emitAlignment(std::max(F.getFunction()->getAlignment(), 8U));
@@ -1084,7 +1085,8 @@ bool JITEmitter::finishFunction(MachineFunction &F) {
     return true;
   }
 
-  emitJumpTableInfo(F.getJumpTableInfo());
+  if (MachineJumpTableInfo *MJTI = F.getJumpTableInfo())
+    emitJumpTableInfo(MJTI);
 
   // FnStart is the start of the text, not the start of the constant pool and
   // other per-function data.
@@ -1404,13 +1406,14 @@ void JITEmitter::initJumpTableInfo(MachineJumpTableInfo *MJTI) {
   for (unsigned i = 0, e = JT.size(); i != e; ++i)
     NumEntries += JT[i].MBBs.size();
 
-  unsigned EntrySize = MJTI->getEntrySize();
+  unsigned EntrySize = MJTI->getEntrySize(*TheJIT->getTargetData());
 
   // Just allocate space for all the jump tables now.  We will fix up the actual
   // MBB entries in the tables after we emit the code for each block, since then
   // we will know the final locations of the MBBs in memory.
   JumpTable = MJTI;
-  JumpTableBase = allocateSpace(NumEntries * EntrySize, MJTI->getAlignment());
+  JumpTableBase = allocateSpace(NumEntries * EntrySize,
+                             MJTI->getEntryAlignment(*TheJIT->getTargetData()));
 }
 
 void JITEmitter::emitJumpTableInfo(MachineJumpTableInfo *MJTI) {
@@ -1420,8 +1423,10 @@ void JITEmitter::emitJumpTableInfo(MachineJumpTableInfo *MJTI) {
   const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
   if (JT.empty() || JumpTableBase == 0) return;
 
+  // FIXME: This should use MachineJumpTableInfo::getEntryKind() instead of
+  // checking for PIC etc.
   if (TargetMachine::getRelocationModel() == Reloc::PIC_) {
-    assert(MJTI->getEntrySize() == 4 && "Cross JIT'ing?");
+    assert(MJTI->getEntrySize(*TheJIT->getTargetData()) == 4&&"Cross JIT'ing?");
     // For each jump table, place the offset from the beginning of the table
     // to the target address.
     int *SlotPtr = (int*)JumpTableBase;
@@ -1437,7 +1442,8 @@ void JITEmitter::emitJumpTableInfo(MachineJumpTableInfo *MJTI) {
       }
     }
   } else {
-    assert(MJTI->getEntrySize() == sizeof(void*) && "Cross JIT'ing?");
+    assert(MJTI->getEntrySize(*TheJIT->getTargetData()) == sizeof(void*) &&
+           "Cross JIT'ing?");
 
     // For each jump table, map each target in the jump table to the address of
     // an emitted MachineBasicBlock.
@@ -1505,9 +1511,9 @@ uintptr_t JITEmitter::getJumpTableEntryAddress(unsigned Index) const {
   const std::vector<MachineJumpTableEntry> &JT = JumpTable->getJumpTables();
   assert(Index < JT.size() && "Invalid jump table index!");
 
-  unsigned Offset = 0;
-  unsigned EntrySize = JumpTable->getEntrySize();
+  unsigned EntrySize = JumpTable->getEntrySize(*TheJIT->getTargetData());
 
+  unsigned Offset = 0;
   for (unsigned i = 0; i < Index; ++i)
     Offset += JT[i].MBBs.size();