Fix a bug where the DWARF emitter in the JIT was not initializing alignment

bytes.  libgcc doesn't seem to mind, but if you pass this DWARF to GDB, it
doesn't like it.  

Also make the JIT memory manager to initialize it's memory to garbage in debug
mode, so that it's easier to find bugs like these in the future.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@79674 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/JITCodeEmitter.h

@@ -19,6 +19,7 @@
 
 #include <string>
 #include "llvm/Support/DataTypes.h"
+#include "llvm/Support/MathExtras.h"
 #include "llvm/CodeGen/MachineCodeEmitter.h"
 
 using namespace std;
@@ -161,18 +162,27 @@ public:
   /// alignment (saturated to BufferEnd of course).
   void emitAlignment(unsigned Alignment) {
     if (Alignment == 0) Alignment = 1;
+    uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
+                                                   Alignment);
+    CurBufferPtr = std::min(NewPtr, BufferEnd);
+  }
 
-    if(Alignment <= (uintptr_t)(BufferEnd-CurBufferPtr)) {
+  /// emitAlignmentWithFill - Similar to emitAlignment, except that the
-      // Move the current buffer ptr up to the specified alignment.
+  /// extra bytes are filled with the provided byte.
-      CurBufferPtr =
+  void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) {
-        (uint8_t*)(((uintptr_t)CurBufferPtr+Alignment-1) &
+    if (Alignment == 0) Alignment = 1;
-                   ~(uintptr_t)(Alignment-1));
+    uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
-    } else {
+                                                   Alignment);
+    // Fail if we don't have room.
+    if (NewPtr > BufferEnd) {
       CurBufferPtr = BufferEnd;
+      return;
+    }
+    while (CurBufferPtr < NewPtr) {
+      *CurBufferPtr++ = Fill;
     }
   }
 
-
   /// emitULEB128Bytes - This callback is invoked when a ULEB128 needs to be
   /// written to the output stream.
   void emitULEB128Bytes(uint64_t Value) {

include/llvm/Support/Dwarf.h

@@ -449,6 +449,7 @@ enum dwarf_constants {
 
   // Call frame instruction encodings
   DW_CFA_extended = 0x00,
+  DW_CFA_nop = 0x00,
   DW_CFA_advance_loc = 0x40,
   DW_CFA_offset = 0x80,
   DW_CFA_restore = 0xc0,

lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp

@@ -396,19 +396,9 @@ unsigned char* JITDwarfEmitter::EmitExceptionTable(MachineFunction* MF,
                         TargetAsmInfo::getULEB128Size(SizeSites) + 
                         SizeSites + SizeActions + SizeTypes;
 
-  unsigned TotalSize = sizeof(int8_t) + // LPStart format
-                       sizeof(int8_t) + // TType format
-                       TargetAsmInfo::getULEB128Size(TypeOffset) + // TType base offset
-                       TypeOffset;
-
-  unsigned SizeAlign = (4 - TotalSize) & 3;
-
   // Begin the exception table.
-  JCE->emitAlignment(4);
+  JCE->emitAlignmentWithFill(4, 0);
-  for (unsigned i = 0; i != SizeAlign; ++i) {
-    JCE->emitByte(0);
   // Asm->EOL("Padding");
-  }
 
   unsigned char* DwarfExceptionTable = (unsigned char*)JCE->getCurrentPCValue();
 
@@ -497,7 +487,7 @@ unsigned char* JITDwarfEmitter::EmitExceptionTable(MachineFunction* MF,
     //Asm->EOL("Filter TypeInfo index");
   }
 
-  JCE->emitAlignment(4);
+  JCE->emitAlignmentWithFill(4, 0);
 
   return DwarfExceptionTable;
 }
@@ -546,7 +536,8 @@ JITDwarfEmitter::EmitCommonEHFrame(const Function* Personality) const {
   std::vector<MachineMove> Moves;
   RI->getInitialFrameState(Moves);
   EmitFrameMoves(0, Moves);
-  JCE->emitAlignment(PointerSize);
+
+  JCE->emitAlignmentWithFill(PointerSize, dwarf::DW_CFA_nop);
 
   JCE->emitInt32At((uintptr_t*)StartCommonPtr,
                    (uintptr_t)((unsigned char*)JCE->getCurrentPCValue() -
@@ -591,7 +582,7 @@ JITDwarfEmitter::EmitEHFrame(const Function* Personality,
   // frame.
   EmitFrameMoves((intptr_t)StartFunction, MMI->getFrameMoves());
 
-  JCE->emitAlignment(PointerSize);
+  JCE->emitAlignmentWithFill(PointerSize, dwarf::DW_CFA_nop);
 
   // Indicate the size of the table
   JCE->emitInt32At((uintptr_t*)StartEHPtr,
@@ -607,7 +598,6 @@ JITDwarfEmitter::EmitEHFrame(const Function* Personality,
     JCE->emitInt32(0);
   }
   
-  
   return StartEHPtr;
 }
 

lib/ExecutionEngine/JIT/JITMemoryManager.cpp

@@ -650,6 +650,10 @@ sys::MemoryBlock DefaultJITMemoryManager::allocateNewSlab(size_t size) {
   }
   LastSlab = B;
   ++NumSlabs;
+  // Initialize the slab to garbage when debugging.
+  if (PoisonMemory) {
+    memset(B.base(), 0xCD, B.size());
+  }
   return B;
 }