Subzero: Aggressive LEA

src/IceInstX86BaseImpl.h

 //===- subzero/src/IceInstX86BaseImpl.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 2007 matching lines @@
   Str << "storeq." << this->getSrc(0)->getType() << " ";
   this->getSrc(1)->dump(Func);
   Str << ", ";
   this->getSrc(0)->dump(Func);
 }
 
 template <typename TraitsType>
 void InstImpl<TraitsType>::InstX86Lea::emit(const Cfg *Func) const {
   if (!BuildDefs::dump())
     return;
+
+  auto *MemOp = llvm::dyn_cast<X86OperandMem>(this->getSrc(0));
+  if (MemOp != nullptr && getFlags().getAggressiveLea() &&
+      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());
+    //TODO: Remove const_cast by emitting code for add directly.

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

TODO(owner)

also, odd that there's no spaced after "//"...

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

Done.

+    // Using the allocator does not help because the constructor for
+    // InstX86Lea takes a non-const Cfg *
+    Add->emit(Func);
+    return;
+  }
+
   Ostream &Str = Func->getContext()->getStrEmit();
   assert(this->getSrcSize() == 1);
   assert(this->getDest()->hasReg());
   Str << "\t"
          "lea" << this->getWidthString(this->getDest()->getType()) << "\t";
   Operand *Src0 = this->getSrc(0);
   if (const auto *Src0Var = llvm::dyn_cast<Variable>(Src0)) {
     Type Ty = Src0Var->getType();
     // lea on x86-32 doesn't accept mem128 operands, so cast VSrc0 to an
     // acceptable type.
@@ skipping 900 matching lines @@
     return;
   Ostream &Str = Func->getContext()->getStrDump();
   Str << "IACA_END";
 }
 
 } // end of namespace X86NAMESPACE
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEINSTX86BASEIMPL_H