Subzero: Use setcc for most fcmp conditions, instead of control flow.

src/IceTargetLoweringX8632.cpp

 //===- subzero/src/IceTargetLoweringX8632.cpp - x86-32 lowering -----------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the TargetLoweringX8632 class, which
@@ skipping 2684 matching lines @@
 
   // Lowering a = fcmp cond, b, c
   //   ucomiss b, c       /* only if C1 != Br_None */
   //                      /* but swap b,c order if SwapOperands==true */
   //   mov a, <default>
   //   j<C1> label        /* only if C1 != Br_None */
   //   j<C2> label        /* only if C2 != Br_None */
   //   FakeUse(a)         /* only if C1 != Br_None */
   //   mov a, !<default>  /* only if C1 != Br_None */
   //   label:             /* only if C1 != Br_None */
+  //
+  // setcc lowering when C1 != Br_None && C2 == Br_None:
+  //   ucomiss b, c       /* but swap b,c order if SwapOperands==true */
+  //   setcc a, C1
   InstFcmp::FCond Condition = Inst->getCondition();
   size_t Index = static_cast<size_t>(Condition);
   assert(Index < TableFcmpSize);
-  if (TableFcmp[Index].SwapScalarOperands) {
-    Operand *Tmp = Src0;
-    Src0 = Src1;
-    Src1 = Tmp;
-  }
+  if (TableFcmp[Index].SwapScalarOperands)
+    std::swap(Src0, Src1);
   bool HasC1 = (TableFcmp[Index].C1 != CondX86::Br_None);
   bool HasC2 = (TableFcmp[Index].C2 != CondX86::Br_None);
   if (HasC1) {
     Src0 = legalize(Src0);
     Operand *Src1RM = legalize(Src1, Legal_Reg | Legal_Mem);
     Variable *T = nullptr;
     _mov(T, Src0);
     _ucomiss(T, Src1RM);
+    if (!HasC2) {
+      assert(TableFcmp[Index].Default);
+      _setcc(Dest, TableFcmp[Index].C1);
+      return;
+    }
   }
   Constant *Default = Ctx->getConstantInt32(TableFcmp[Index].Default);
   _mov(Dest, Default);
   if (HasC1) {
     InstX8632Label *Label = InstX8632Label::create(Func, this);
     _br(TableFcmp[Index].C1, Label);
     if (HasC2) {
       _br(TableFcmp[Index].C2, Label);
     }
     Constant *NonDefault = Ctx->getConstantInt32(!TableFcmp[Index].Default);
@@ skipping 2304 matching lines @@
   case FT_Asm:
   case FT_Iasm: {
     OstreamLocker L(Ctx);
     emitConstantPool<PoolTypeConverter<float>>(Ctx);
     emitConstantPool<PoolTypeConverter<double>>(Ctx);
   } break;
   }
 }
 
 } // end of namespace Ice