Use three-address form of imul

src/IceInstX86BaseImpl.h

Index: src/IceInstX86BaseImpl.h
diff --git a/src/IceInstX86BaseImpl.h b/src/IceInstX86BaseImpl.h
index c6ebd3a4ad43a94193b9004364151f87545ecdb3..5321dc4e373113a140ed938c621182a93741eec3 100644
--- a/src/IceInstX86BaseImpl.h
+++ b/src/IceInstX86BaseImpl.h
@@ -1330,8 +1330,7 @@ void InstX86Imul<Machine>::emitIAS(const Cfg *Func) const {
         &InstX86Base<Machine>::Traits::Assembler::imul};
     emitIASOpTyGPR<Machine>(Func, Ty, this->getSrc(1), Emitter);
   } else {
-    // We only use imul as a two-address instruction even though there is a 3
-    // operand version when one of the operands is a constant.
+    // The two-address version is used when multiplying by a non-constant.

[Jim Stichnoth, 2015/09/25 21:02:10]

or for the 8-bit version (right?)

[sehr, 2015/09/25 23:04:40]

Done.

     assert(Var == this->getSrc(0));
     static const typename InstX86Base<
         Machine>::Traits::Assembler::GPREmitterRegOp Emitter = {
@@ -1343,6 +1342,42 @@ void InstX86Imul<Machine>::emitIAS(const Cfg *Func) const {
 }
 
 template <class Machine>
+void InstX86ImulImm<Machine>::emit(const Cfg *Func) const {
+  if (!BuildDefs::dump())
+    return;
+  Ostream &Str = Func->getContext()->getStrEmit();
+  assert(this->getSrcSize() == 2);
+  Variable *Dest = this->getDest();

[Jim Stichnoth, 2015/09/25 21:02:10]

Add an assert that the type is i16 or i32.  (The emitIAS() method could also
have that assert, though the assembler already asserts that.)

[sehr, 2015/09/25 23:04:40]

Done.

+  assert(llvm::isa<Constant>(this->getSrc(1)));
+  Str << "\timul" << this->getWidthString(Dest->getType()) << "\t";
+  this->getSrc(1)->emit(Func);
+  Str << ", ";
+  this->getSrc(0)->emit(Func);
+  Str << ", ";
+  Dest->emit(Func);
+}
+
+template <class Machine>
+void InstX86ImulImm<Machine>::emitIAS(const Cfg *Func) const {
+  assert(this->getSrcSize() == 2);
+  const Variable *Dest = this->getDest();
+  Type Ty = Dest->getType();
+  assert(llvm::isa<Constant>(this->getSrc(1)));
+  static const typename InstX86Base<Machine>::Traits::Assembler::
+      template ThreeOpImmEmitter<
+          typename InstX86Base<Machine>::Traits::RegisterSet::GPRRegister,
+          typename InstX86Base<Machine>::Traits::RegisterSet::GPRRegister>
+          Emitter = {&InstX86Base<Machine>::Traits::Assembler::imul_imm,
+                     &InstX86Base<Machine>::Traits::Assembler::imul_imm};
+  emitIASThreeOpImmOps<
+      Machine, typename InstX86Base<Machine>::Traits::RegisterSet::GPRRegister,
+      typename InstX86Base<Machine>::Traits::RegisterSet::GPRRegister,
+      InstX86Base<Machine>::Traits::RegisterSet::getEncodedGPR,
+      InstX86Base<Machine>::Traits::RegisterSet::getEncodedGPR>(
+      Func, Ty, Dest, this->getSrc(0), this->getSrc(1), Emitter);
+}
+
+template <class Machine>
 void InstX86Insertps<Machine>::emitIAS(const Cfg *Func) const {
   assert(this->getSrcSize() == 3);
   assert(static_cast<typename InstX86Base<Machine>::Traits::TargetLowering *>(