Subzero: Simplify the icmp i64 lowering.

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 2692 matching lines @@
       _cmp(Src0RM, Src1);
       _br(getIcmp32Mapping(Inst->getCondition()), NextBr->getTargetTrue(),
           NextBr->getTargetFalse());
       // Skip over the following branch instruction.
       Context.advanceNext();
       return;
     }
   }
 
   // a=icmp cond, b, c ==> cmp b,c; a=1; br cond,L1; FakeUse(a); a=0; L1:
-  Constant *Zero = Ctx->getConstantZero(IceType_i32);
-  Constant *One = Ctx->getConstantInt32(1);
   if (Src0->getType() == IceType_i64) {
     InstIcmp::ICond Condition = Inst->getCondition();
     size_t Index = static_cast<size_t>(Condition);
     assert(Index < TableIcmp64Size);
     Operand *Src0LoRM = legalize(loOperand(Src0), Legal_Reg | Legal_Mem);
     Operand *Src0HiRM = legalize(hiOperand(Src0), Legal_Reg | Legal_Mem);
     Operand *Src1LoRI = legalize(loOperand(Src1), Legal_Reg | Legal_Imm);
     Operand *Src1HiRI = legalize(hiOperand(Src1), Legal_Reg | Legal_Imm);
-    if (Condition == InstIcmp::Eq || Condition == InstIcmp::Ne) {
-      InstX8632Label *Label = InstX8632Label::create(Func, this);

[Jim Stichnoth, 2015/05/06 22:24:21]

This block of code is entirely removed.

-      _mov(Dest, (Condition == InstIcmp::Eq ? Zero : One));
-      _cmp(Src0LoRM, Src1LoRI);
-      _br(CondX86::Br_ne, Label);
-      _cmp(Src0HiRM, Src1HiRI);
-      _br(CondX86::Br_ne, Label);
-      _mov_nonkillable(Dest, (Condition == InstIcmp::Eq ? One : Zero));
-      Context.insert(Label);
-    } else {
-      InstX8632Label *LabelFalse = InstX8632Label::create(Func, this);
-      InstX8632Label *LabelTrue = InstX8632Label::create(Func, this);
-      _mov(Dest, One);
-      _cmp(Src0HiRM, Src1HiRI);
+    Constant *Zero = Ctx->getConstantZero(IceType_i32);
+    Constant *One = Ctx->getConstantInt32(1);
+    InstX8632Label *LabelFalse = InstX8632Label::create(Func, this);
+    InstX8632Label *LabelTrue = InstX8632Label::create(Func, this);
+    _mov(Dest, One);
+    _cmp(Src0HiRM, Src1HiRI);
+    if (TableIcmp64[Index].C1 != CondX86::Br_None)
       _br(TableIcmp64[Index].C1, LabelTrue);

[Jim Stichnoth, 2015/05/06 22:24:21]

These two branch instructions are now created only when the condition is not
Br_None.

+    if (TableIcmp64[Index].C2 != CondX86::Br_None)
       _br(TableIcmp64[Index].C2, LabelFalse);
-      _cmp(Src0LoRM, Src1LoRI);
-      _br(TableIcmp64[Index].C3, LabelTrue);
-      Context.insert(LabelFalse);
-      _mov_nonkillable(Dest, Zero);
-      Context.insert(LabelTrue);
-    }
+    _cmp(Src0LoRM, Src1LoRI);
+    _br(TableIcmp64[Index].C3, LabelTrue);
+    Context.insert(LabelFalse);
+    _mov_nonkillable(Dest, Zero);
+    Context.insert(LabelTrue);
     return;
   }
 
   // cmp b, c
   Operand *Src0RM =
       legalize(Src0, IsSrc1ImmOrReg ? (Legal_Reg | Legal_Mem) : Legal_Reg);
   _cmp(Src0RM, Src1);
   _setcc(Dest, getIcmp32Mapping(Inst->getCondition()));
 }
 
@@ skipping 2128 matching lines @@
   case FT_Asm:
   case FT_Iasm: {
     OstreamLocker L(Ctx);
     emitConstantPool<PoolTypeConverter<float>>(Ctx);
     emitConstantPool<PoolTypeConverter<double>>(Ctx);
   } break;
   }
 }
 
 } // end of namespace Ice