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.

llvm-svn: 79674

4 files changed, 40 insertions, 35 deletions

diff --git a/llvm/include/llvm/CodeGen/JITCodeEmitter.h b/llvm/include/llvm/CodeGen/JITCodeEmitter.h
index c3f95b41989..180783a4d62 100644
--- a/llvm/include/llvm/CodeGen/JITCodeEmitter.h
+++ b/llvm/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;
@@ -161,17 +162,26 @@ 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)) {
-      // Move the current buffer ptr up to the specified alignment.
-      CurBufferPtr =
-        (uint8_t*)(((uintptr_t)CurBufferPtr+Alignment-1) &
-                   ~(uintptr_t)(Alignment-1));
-    } else {
+  /// emitAlignmentWithFill - Similar to emitAlignment, except that the
+  /// extra bytes are filled with the provided byte.
+  void emitAlignmentWithFill(unsigned Alignment, uint8_t Fill) {
+    if (Alignment == 0) Alignment = 1;
+    uint8_t *NewPtr = (uint8_t*)RoundUpToAlignment((uintptr_t)CurBufferPtr,
+                                                   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.
diff --git a/llvm/include/llvm/Support/Dwarf.h b/llvm/include/llvm/Support/Dwarf.h
index 55838b8144b..bfccc522b97 100644
--- a/llvm/include/llvm/Support/Dwarf.h
+++ b/llvm/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,
diff --git a/llvm/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp b/llvm/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
index c661168487a..a3a050635fe 100644
--- a/llvm/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
+++ b/llvm/lib/ExecutionEngine/JIT/JITDwarfEmitter.cpp
@@ -396,20 +396,10 @@ 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);
-  for (unsigned i = 0; i != SizeAlign; ++i) {
-    JCE->emitByte(0);
-    // Asm->EOL("Padding");
-  }
-  
+  JCE->emitAlignmentWithFill(4, 0);
+  // Asm->EOL("Padding");
+
   unsigned char* DwarfExceptionTable = (unsigned char*)JCE->getCurrentPCValue();
 
   // Emit the header.
@@ -496,8 +486,8 @@ unsigned char* JITDwarfEmitter::EmitExceptionTable(MachineFunction* MF,
     JCE->emitULEB128Bytes(TypeID);
     //Asm->EOL("Filter TypeInfo index");
   }
-  
-  JCE->emitAlignment(4);
+
+  JCE->emitAlignmentWithFill(4, 0);
 
   return DwarfExceptionTable;
 }
@@ -546,11 +536,12 @@ JITDwarfEmitter::EmitCommonEHFrame(const Function* Personality) const {
   std::vector<MachineMove> Moves;
   RI->getInitialFrameState(Moves);
   EmitFrameMoves(0, Moves);
-  JCE->emitAlignment(PointerSize);
-  
-  JCE->emitInt32At((uintptr_t*)StartCommonPtr, 
-              (uintptr_t)((unsigned char*)JCE->getCurrentPCValue() - 
-                          FrameCommonBeginPtr));
+
+  JCE->emitAlignmentWithFill(PointerSize, dwarf::DW_CFA_nop);
+
+  JCE->emitInt32At((uintptr_t*)StartCommonPtr,
+                   (uintptr_t)((unsigned char*)JCE->getCurrentPCValue() -
+                               FrameCommonBeginPtr));
 
   return StartCommonPtr;
 }
@@ -590,14 +581,14 @@ JITDwarfEmitter::EmitEHFrame(const Function* Personality,
   // Indicate locations of function specific  callee saved registers in
   // 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, 
-              (uintptr_t)((unsigned char*)JCE->getCurrentPCValue() - 
-                          StartEHPtr));
-  
+  JCE->emitInt32At((uintptr_t*)StartEHPtr,
+                   (uintptr_t)((unsigned char*)JCE->getCurrentPCValue() -
+                               StartEHPtr));
+
   // Double zeroes for the unwind runtime
   if (PointerSize == 8) {
     JCE->emitInt64(0);
@@ -606,7 +597,6 @@ JITDwarfEmitter::EmitEHFrame(const Function* Personality,
     JCE->emitInt32(0);
     JCE->emitInt32(0);
   }
-
   
   return StartEHPtr;
 }
diff --git a/llvm/lib/ExecutionEngine/JIT/JITMemoryManager.cpp b/llvm/lib/ExecutionEngine/JIT/JITMemoryManager.cpp
index f40e67d90c1..57dd45813e9 100644
--- a/llvm/lib/ExecutionEngine/JIT/JITMemoryManager.cpp
+++ b/llvm/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;
 }