Subzero: Aggressive LEA

src/IceInstX86Base.h

 //===- subzero/src/IceInstX86Base.h - Generic x86 instructions -*- C++ -*--===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 602 matching lines @@
       this->getSrc(0)->emit(Func);
       Str << ", ";
       this->getDest()->emit(Func);
     }
     void emitIAS(const Cfg *Func) const override {
       assert(this->getSrcSize() == 1);
       const Variable *Var = this->getDest();
       Type Ty = Var->getType();
       const Operand *Src = this->getSrc(0);
       constexpr bool IsLea = K == InstX86Base::Lea;
+      if (IsLea) {
+        auto *MemOp = llvm::dyn_cast<X86OperandMem>(this->getSrc(0));
+        if (MemOp != nullptr && getFlags().getAggressiveLea() &&

[Jim Stichnoth, 2016/08/01 21:08:41]

This would be better as a private method of the class, and used here for
emitIAS() and also for emit().

Along those lines, the helper could also do the work of creating the new
InstX86Add instruction, which would leave the const_cast in just one place.

The helper method name might be "deoptToAddOrNull()" or something similar, and
used like this:

  if (Inst *Add = deoptToAddOrNull()) {
    Add->emitIAS(Func);
    return;
  }

[manasijm, 2016/08/01 23:14:58]

Done.

+            MemOp->getBase()->getRegNum() == this->getDest()->getRegNum() &&
+            MemOp->getIndex() == nullptr && MemOp->getShift() == 0) {
+          // Reverts back to Add when the Lea is a 2-address instruction
+          auto *Add = InstImpl<TraitsType>::InstX86Add::create(
+              const_cast<Cfg *>(Func), this->getDest(), MemOp->getOffset());
+          Add->emitIAS(Func);
+          return;
+        }
+      }
       emitIASRegOpTyGPR(Func, IsLea, Ty, Var, Src, Emitter);
     }
     void dump(const Cfg *Func) const override {
       if (!BuildDefs::dump())
         return;
       Ostream &Str = Func->getContext()->getStrDump();
       this->dumpDest(Func);
       Str << " = " << Opcode << "." << this->getSrc(0)->getType() << " ";
       this->dumpSources(Func);
     }
@@ skipping 2978 matching lines @@
           &InstImpl<TraitsType>::Assembler::punpckldq};                        \
   }                                                                            \
   }
 
 } // end of namespace X86NAMESPACE
 } // end of namespace Ice
 
 #include "IceInstX86BaseImpl.h"
 
 #endif // SUBZERO_SRC_ICEINSTX86BASE_H