Subzero: Make sure alloca with align=0 is handled correctly.

src/IceTargetLoweringX8632.cpp

 //===- subzero/src/IceTargetLoweringX8632.cpp - x86-32 lowering -----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the TargetLoweringX8632 class, which
@@ skipping 1100 matching lines @@
   // aligned before the alloca.  All the alloca code ensures that the
   // stack alignment is preserved after the alloca.  The stack alignment
   // restriction can be relaxed in some cases.
   NeedsStackAlignment = true;
 
   // TODO(sehr,stichnot): minimize the number of adjustments of esp, etc.
   Variable *esp = getPhysicalRegister(Reg_esp);
   Operand *TotalSize = legalize(Inst->getSizeInBytes());
   Variable *Dest = Inst->getDest();
   uint32_t AlignmentParam = Inst->getAlignInBytes();
+  // For default align=0, set it to the real value 1, to avoid any
+  // bit-manipulation problems below.
+  AlignmentParam = std::max(AlignmentParam, 1u);
 
   // LLVM enforces power of 2 alignment.
   assert((AlignmentParam & (AlignmentParam - 1)) == 0);
   assert((X86_STACK_ALIGNMENT_BYTES & (X86_STACK_ALIGNMENT_BYTES - 1)) == 0);
 
   uint32_t Alignment = std::max(AlignmentParam, X86_STACK_ALIGNMENT_BYTES);
   if (Alignment > X86_STACK_ALIGNMENT_BYTES) {
     _and(esp, Ctx->getConstantInt(IceType_i32, -Alignment));
   }
   if (ConstantInteger *ConstantTotalSize =
@@ skipping 3323 matching lines @@
     Str << "\t.align\t" << Align << "\n";
     Str << MangledName << ":\n";
     for (SizeT i = 0; i < Size; ++i) {
       Str << "\t.byte\t" << (((unsigned)Data[i]) & 0xff) << "\n";
     }
     Str << "\t.size\t" << MangledName << ", " << Size << "\n";
   }
 }
 
 } // end of namespace Ice