Subzero: Aggressive LEA

src/IceTargetLoweringX86BaseImpl.h

Index: src/IceTargetLoweringX86BaseImpl.h
diff --git a/src/IceTargetLoweringX86BaseImpl.h b/src/IceTargetLoweringX86BaseImpl.h
index 2acd3312d9b9b74c6a30853cc7cabcab2d2ff59d..e2c96f8b9e6b5c72a75a13b5d95b0b6acbb29c95 100644
--- a/src/IceTargetLoweringX86BaseImpl.h
+++ b/src/IceTargetLoweringX86BaseImpl.h
@@ -2183,11 +2183,28 @@ void TargetX86Base<TraitsType>::lowerArithmetic(const InstArithmetic *Instr) {
   case InstArithmetic::_num:
     llvm_unreachable("Unknown arithmetic operator");
     break;
-  case InstArithmetic::Add:
-    _mov(T, Src0);
-    _add(T, Src1);
-    _mov(Dest, T);
-    break;
+  case InstArithmetic::Add: {
+    bool ConvertedToLea = false;
+    if (getFlags().getAggressiveLea() &&

[Jim Stichnoth, 2016/07/29 14:27:26]

I wonder if this conditional would be clearer as something like this:

if (auto *Const = llvm::dyn_cast<Constant>(Instr->getSrc(1))) {
  const bool ValidType = (Ty == IceType_i32 ||
                          (Ty == IceType_i64 && Traits::Is64Bit));
  const bool ValidKind = (llvm::isa<ConstantInteger32>(Const) ||
                          llvm::isa<ConstantRelocatable>(Const));
  if (getFlags().getAggressiveLea() && ValidType && ValidKind) {
    ...
    break;
  }
}

[manasijm, 2016/08/01 19:36:21]

Done.

+        (Ty == IceType_i32 || (Ty == IceType_i64 && Traits::Is64Bit))) {
+      Constant *Const = llvm::dyn_cast<Constant>(Instr->getSrc(1));

[Jim Stichnoth, 2016/07/29 14:27:26]

auto *Const

[manasijm, 2016/08/01 19:36:21]

Done.

+      if (Const != nullptr && (llvm::isa<ConstantInteger32>(Const) ||
+                               llvm::isa<ConstantRelocatable>(Const))) {
+        auto *Var = legalizeToReg(Src0);
+        auto *Mem =
+            Traits::X86OperandMem::create(Func, IceType_void, Var, Const);
+        T = makeReg(Ty);
+        _lea(T, _sandbox_mem_reference(Mem));
+        _mov(Dest, T);
+        ConvertedToLea = true;

[Jim Stichnoth, 2016/07/29 14:27:26]

I would just put a "break;" here, and remove ConvertedToLea entirely.

[manasijm, 2016/08/01 19:36:21]

Done.

+      }
+    }
+    if (!ConvertedToLea) {
+      _mov(T, Src0);
+      _add(T, Src1);
+      _mov(Dest, T);
+    }
+  } break;
   case InstArithmetic::And:
     _mov(T, Src0);
     _and(T, Src1);