Subzero: Force ebp-based frame when an alloca has a large alignment.

src/IceTargetLoweringX86BaseImpl.h

 //===- subzero/src/IceTargetLoweringX86BaseImpl.h - x86 lowering -*- C++ -*-==//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 938 matching lines @@
   // bit-manipulation problems below.
   AlignmentParam = std::max(AlignmentParam, 1u);
 
   // LLVM enforces power of 2 alignment.
   assert(llvm::isPowerOf2_32(AlignmentParam));
   assert(llvm::isPowerOf2_32(Traits::X86_STACK_ALIGNMENT_BYTES));
 
   uint32_t Alignment =
       std::max(AlignmentParam, Traits::X86_STACK_ALIGNMENT_BYTES);
   if (Alignment > Traits::X86_STACK_ALIGNMENT_BYTES) {
+    IsEbpBasedFrame = true;
     _and(esp, Ctx->getConstantInt32(-Alignment));
   }
   if (const auto *ConstantTotalSize =
           llvm::dyn_cast<ConstantInteger32>(TotalSize)) {
     uint32_t Value = ConstantTotalSize->getValue();
     Value = Utils::applyAlignment(Value, Alignment);
     if (Inst->getKnownFrameOffset()) {
       _adjust_stack(Value);
       FixedAllocaSizeBytes += Value;
     } else {
@@ skipping 4888 matching lines @@
   }
   // the offset is not eligible for blinding or pooling, return the original
   // mem operand
   return MemOperand;
 }
 
 } // end of namespace X86Internal
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICETARGETLOWERINGX86BASEIMPL_H