[llvm-commits] [llvm] r52440 - in /llvm/trunk: lib/Transforms/Scalar/InstructionCombining.cpp test/Transforms/InstCombine/sext-misc.ll

[Chris Lattner]

Will do, sorry for the breakage!

On Jun 18, 2008, at 9:14 AM, Dan Gohman wrote:

> Hi Chris
>
> sext-misc.ll now fails with three sext instructions that aren't
> being eliminated that previously were. Can you investigate?
>
> Thanks,
>
> Dan
>
> On Tue, June 17, 2008 9:00 pm, Chris Lattner wrote:
>> Author: lattner
>> Date: Tue Jun 17 23:00:49 2008
>> New Revision: 52440
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=52440&view=rev
>> Log:
>> make truncate/sext elimination capable of changing phi's.  This
>> implements rdar://6013816 and the testcase in
>> Transforms/InstCombine/sext-misc.ll.
>>
>> Modified:
>>    llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
>>    llvm/trunk/test/Transforms/InstCombine/sext-misc.ll
>>
>> Modified: llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp?rev=52440&r1=52439&r2=52440&view=diff
>>
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =
>> =====================================================================
>> --- llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp  
>> (original)
>> +++ llvm/trunk/lib/Transforms/Scalar/InstructionCombining.cpp Tue  
>> Jun 17
>> 23:00:49 2008
>> @@ -6838,6 +6838,16 @@
>> ///
>> /// This is a truncation operation if Ty is smaller than V- 
>> >getType(), or
>> an
>> /// extension operation if Ty is larger.
>> +///
>> +/// If CastOpc is a truncation, then Ty will be a type smaller  
>> than V.
>> We
>> +/// should return true if trunc(V) can be computed by computing V  
>> in the
>> smaller
>> +/// type.  If V is an instruction, then trunc(inst(x,y)) can be  
>> computed
>> as
>> +/// inst(trunc(x),trunc(y)), which only makes sense if x and y can  
>> be
>> +/// efficiently truncated.
>> +///
>> +/// If CastOpc is a sext or zext, we are asking if the low bits of  
>> the
>> value can
>> +/// bit computed in a larger type, which is then and'd or  
>> sext_in_reg'd
>> to get
>> +/// the final result.
>> bool InstCombiner::CanEvaluateInDifferentType(Value *V, const  
>> IntegerType
>> *Ty,
>>                                               unsigned CastOpc,
>>                                               int &NumCastsRemoved) {
>> @@ -6858,7 +6868,7 @@
>>       // If the first operand is itself a cast, and is eliminable,  
>> do not
>> count
>>       // this as an eliminable cast.  We would prefer to eliminate  
>> those
>> two
>>       // casts first.
>> -      if (!isa<CastInst>(I->getOperand(0)))
>> +      if (!isa<CastInst>(I->getOperand(0)) && I->hasOneUse())
>>         ++NumCastsRemoved;
>>       return true;
>>     }
>> @@ -6923,8 +6933,17 @@
>>     // of casts in the input.
>>     if (I->getOpcode() == CastOpc)
>>       return true;
>> -
>>     break;
>> +
>> +  case Instruction::PHI: {
>> +    // We can change a phi if we can change all operands.
>> +    PHINode *PN = cast<PHINode>(I);
>> +    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; + 
>> +i)
>> +      if (!CanEvaluateInDifferentType(PN->getIncomingValue(i), Ty,
>> CastOpc,
>> +                                      NumCastsRemoved))
>> +        return false;
>> +    return true;
>> +  }
>>   default:
>>     // TODO: Can handle more cases here.
>>     break;
>> @@ -6957,7 +6976,7 @@
>>     Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty,  
>> isSigned);
>>     Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty,  
>> isSigned);
>>     Res = BinaryOperator::Create((Instruction::BinaryOps)I- 
>> >getOpcode(),
>> -                                 LHS, RHS, I->getName());
>> +                                 LHS, RHS);
>>     break;
>>   }
>>   case Instruction::Trunc:
>> @@ -6969,16 +6988,27 @@
>>     if (I->getOperand(0)->getType() == Ty)
>>       return I->getOperand(0);
>>
>> -    // Otherwise, must be the same type of case, so just reinsert  
>> a new
>> one.
>> +    // Otherwise, must be the same type of cast, so just reinsert  
>> a new
>> one.
>>     Res = CastInst::Create(cast<CastInst>(I)->getOpcode(),
>> I->getOperand(0),
>> -                           Ty, I->getName());
>> +                           Ty);
>>     break;
>> +  case Instruction::PHI: {
>> +    PHINode *OPN = cast<PHINode>(I);
>> +    PHINode *NPN = PHINode::Create(Ty);
>> +    for (unsigned i = 0, e = OPN->getNumIncomingValues(); i != e; + 
>> +i) {
>> +      Value *V =EvaluateInDifferentType(OPN->getIncomingValue(i),  
>> Ty,
>> isSigned);
>> +      NPN->addIncoming(V, OPN->getIncomingBlock(i));
>> +    }
>> +    Res = NPN;
>> +    break;
>> +  }
>>   default:
>>     // TODO: Can handle more cases here.
>>     assert(0 && "Unreachable!");
>>     break;
>>   }
>>
>> +  Res->takeName(I);
>>   return InsertNewInstBefore(Res, *I);
>> }
>>
>>
>> Modified: llvm/trunk/test/Transforms/InstCombine/sext-misc.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/sext-misc.ll?rev=52440&r1=52439&r2=52440&view=diff
>>
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> = 
>> =====================================================================
>> --- llvm/trunk/test/Transforms/InstCombine/sext-misc.ll (original)
>> +++ llvm/trunk/test/Transforms/InstCombine/sext-misc.ll Tue Jun 17
>> 23:00:49 2008
>> @@ -1,6 +1,4 @@
>> ; RUN: llvm-as < %s | opt -instcombine | llvm-dis | not grep sext
>> -; RUN: llvm-as < %s | llc -march=x86-64 | not grep movslq
>> -; RUN: llvm-as < %s | llc -march=x86 | not grep sar
>>
>> declare i32 @llvm.ctpop.i32(i32)
>> declare i32 @llvm.ctlz.i32(i32)
>> @@ -50,3 +48,18 @@
>>   %n = sext i16 %s to i32
>>   ret i32 %n
>> }
>> +
>> +; rdar://6013816
>> +define i16 @test(i16 %t, i1 %cond) nounwind {
>> +entry:
>> +	br i1 %cond, label %T, label %F
>> +T:
>> +	%t2 = sext i16 %t to i32
>> +	br label %F
>> +
>> +F:
>> +	%V = phi i32 [%t2, %T], [42, %entry]
>> +	%W = trunc i32 %V to i16
>> +	ret i16 %W
>> +}
>> +
>>
>>
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