[llvm] r266987 - Refactor implied condition logic from ValueTracking directly into CmpInst. NFC.
Chad Rosier via llvm-commits
llvm-commits at lists.llvm.org
Thu Apr 21 09:24:24 PDT 2016
Committed r266998. Thanks, Philip.
-----Original Message-----
From: Philip Reames [mailto:listmail at philipreames.com]
Sent: Thursday, April 21, 2016 12:01 PM
To: mcrosier at codeaurora.org; llvm-commits at lists.llvm.org
Subject: Re: [llvm] r266987 - Refactor implied condition logic from ValueTracking directly into CmpInst. NFC.
SGTM. Not perfect, but definitely better. Sometimes that's all you can do.
On 04/21/2016 08:57 AM, Chad Rosier wrote:
> Hi Philip,
> I agree it's difficult to come up with a meaningful name. How about isImpliedTrueByMatchingCmp/isImpliedFalseByMatchingCmp?
>
> Chad
>
> -----Original Message-----
> From: Philip Reames [mailto:listmail at philipreames.com]
> Sent: Thursday, April 21, 2016 10:48 AM
> To: Chad Rosier <mcrosier at codeaurora.org>; llvm-commits at lists.llvm.org
> Subject: Re: [llvm] r266987 - Refactor implied condition logic from ValueTracking directly into CmpInst. NFC.
>
> The naming of isTrueWhenOperandsMatch and isFalseWhenOperandsMatch
> aren't exactly clear. Reading through code, I'd have no idea what they
> do. Possibly: isImpliedByMatchingCompare(Pred)? I don't really like
> that either, but its better than what we have.
>
> Philip
>
>
> On 04/21/2016 07:04 AM, Chad Rosier via llvm-commits wrote:
>> Author: mcrosier
>> Date: Thu Apr 21 09:04:54 2016
>> New Revision: 266987
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=266987&view=rev
>> Log:
>> Refactor implied condition logic from ValueTracking directly into CmpInst. NFC.
>>
>> Differential Revision: http://reviews.llvm.org/D19330
>>
>> Modified:
>> llvm/trunk/include/llvm/IR/InstrTypes.h
>> llvm/trunk/lib/Analysis/ValueTracking.cpp
>> llvm/trunk/lib/IR/Instructions.cpp
>>
>> Modified: llvm/trunk/include/llvm/IR/InstrTypes.h
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/InstrTypes.h?rev=266987&r1=266986&r2=266987&view=diff
>> ==============================================================================
>> --- llvm/trunk/include/llvm/IR/InstrTypes.h (original)
>> +++ llvm/trunk/include/llvm/IR/InstrTypes.h Thu Apr 21 09:04:54 2016
>> @@ -1067,6 +1067,18 @@ public:
>> return isFalseWhenEqual(getPredicate());
>> }
>>
>> + /// @brief Determine if Pred1 implies Pred2 is true when two compares have
>> + /// matching operands.
>> + bool isTrueWhenOperandsMatch(Predicate Pred2) {
>> + return isTrueWhenOperandsMatch(getPredicate(), Pred2);
>> + }
>> +
>> + /// @brief Determine if Pred1 implies Pred2 is false when two compares have
>> + /// matching operands.
>> + bool isFalseWhenOperandsMatch(Predicate Pred2) {
>> + return isFalseWhenOperandsMatch(getPredicate(), Pred2);
>> + }
>> +
>> /// @returns true if the predicate is unsigned, false otherwise.
>> /// @brief Determine if the predicate is an unsigned operation.
>> static bool isUnsigned(Predicate predicate);
>> @@ -1087,6 +1099,14 @@ public:
>> /// Determine if the predicate is false when comparing a value with itself.
>> static bool isFalseWhenEqual(Predicate predicate);
>>
>> + /// Determine if Pred1 implies Pred2 is true when two compares have matching
>> + /// operands.
>> + static bool isTrueWhenOperandsMatch(Predicate Pred1, Predicate Pred2);
>> +
>> + /// Determine if Pred1 implies Pred2 is false when two compares have matching
>> + /// operands.
>> + static bool isFalseWhenOperandsMatch(Predicate Pred1, Predicate Pred2);
>> +
>> /// @brief Methods for support type inquiry through isa, cast, and dyn_cast:
>> static inline bool classof(const Instruction *I) {
>> return I->getOpcode() == Instruction::ICmp ||
>>
>> Modified: llvm/trunk/lib/Analysis/ValueTracking.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ValueTracking.cpp?rev=266987&r1=266986&r2=266987&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Analysis/ValueTracking.cpp (original)
>> +++ llvm/trunk/lib/Analysis/ValueTracking.cpp Thu Apr 21 09:04:54 2016
>> @@ -3935,61 +3935,11 @@ static Optional<bool> isImpliedCondMatch
>> std::swap(BLHS, BRHS);
>> BPred = ICmpInst::getSwappedPredicate(BPred);
>> }
>> -
>> - // If the predicates match, then we know the first condition implies the
>> - // second is true.
>> - if (APred == BPred)
>> + if (CmpInst::isTrueWhenOperandsMatch(APred, BPred))
>> return true;
>> -
>> - // If an inverted APred matches BPred, we can infer the second condition is
>> - // false.
>> - if (CmpInst::getInversePredicate(APred) == BPred)
>> + if (CmpInst::isFalseWhenOperandsMatch(APred, BPred))
>> return false;
>>
>> - // If a swapped APred matches BPred, we can infer the second condition is
>> - // false in many cases.
>> - if (CmpInst::getSwappedPredicate(APred) == BPred) {
>> - switch (APred) {
>> - default:
>> - break;
>> - case CmpInst::ICMP_UGT: // A >u B implies A <u B is false.
>> - case CmpInst::ICMP_ULT: // A <u B implies A >u B is false.
>> - case CmpInst::ICMP_SGT: // A >s B implies A <s B is false.
>> - case CmpInst::ICMP_SLT: // A <s B implies A >s B is false.
>> - return false;
>> - }
>> - }
>> -
>> - // The predicates must match sign or at least one of them must be an equality
>> - // comparison (which is signless).
>> - if (ICmpInst::isSigned(APred) != ICmpInst::isSigned(BPred) &&
>> - !ICmpInst::isEquality(APred) && !ICmpInst::isEquality(BPred))
>> - return None;
>> -
>> - switch (APred) {
>> - default:
>> - break;
>> - case CmpInst::ICMP_EQ:
>> - // A == B implies A > B and A < B are false.
>> - if (CmpInst::isFalseWhenEqual(BPred))
>> - return false;
>> -
>> - break;
>> - case CmpInst::ICMP_UGT:
>> - case CmpInst::ICMP_ULT:
>> - case CmpInst::ICMP_SGT:
>> - case CmpInst::ICMP_SLT:
>> - // A > B implies A == B is false.
>> - // A < B implies A == B is false.
>> - if (BPred == CmpInst::ICMP_EQ)
>> - return false;
>> -
>> - // A > B implies A != B is true.
>> - // A < B implies A != B is true.
>> - if (BPred == CmpInst::ICMP_NE)
>> - return true;
>> - break;
>> - }
>> return None;
>> }
>>
>>
>> Modified: llvm/trunk/lib/IR/Instructions.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/Instructions.cpp?rev=266987&r1=266986&r2=266987&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/IR/Instructions.cpp (original)
>> +++ llvm/trunk/lib/IR/Instructions.cpp Thu Apr 21 09:04:54 2016
>> @@ -3597,6 +3597,58 @@ bool CmpInst::isFalseWhenEqual(Predicate
>> }
>> }
>>
>> +bool CmpInst::isTrueWhenOperandsMatch(Predicate Pred1, Predicate Pred2) {
>> + // If the predicates match, then we know the first condition implies the
>> + // second is true.
>> + if (Pred1 == Pred2)
>> + return true;
>> +
>> + switch (Pred1) {
>> + default:
>> + break;
>> + case ICMP_UGT: // A >u B implies A != B is true.
>> + case ICMP_ULT: // A <u B implies A != B is true.
>> + case ICMP_SGT: // A >s B implies A != B is true.
>> + case ICMP_SLT: // A <s B implies A != B is true.
>> + return Pred2 == ICMP_NE;
>> + }
>> + return false;
>> +}
>> +
>> +bool CmpInst::isFalseWhenOperandsMatch(Predicate Pred1, Predicate Pred2) {
>> + // If an inverted Pred1 matches Pred2, we can infer the second condition is
>> + // false.
>> + if (getInversePredicate(Pred1) == Pred2)
>> + return true;
>> +
>> + // If a swapped Pred1 matches Pred2, we can infer the second condition is
>> + // false in many cases.
>> + if (getSwappedPredicate(Pred1) == Pred2) {
>> + switch (Pred1) {
>> + default:
>> + break;
>> + case ICMP_UGT: // A >u B implies A <u B is false.
>> + case ICMP_ULT: // A <u B implies A >u B is false.
>> + case ICMP_SGT: // A >s B implies A <s B is false.
>> + case ICMP_SLT: // A <s B implies A >s B is false.
>> + return true;
>> + }
>> + }
>> + // A == B implies A > B and A < B are false.
>> + if (Pred1 == ICMP_EQ && isFalseWhenEqual(Pred2))
>> + return true;
>> +
>> + switch (Pred1) {
>> + default:
>> + break;
>> + case ICMP_UGT: // A >u B implies A == B is false.
>> + case ICMP_ULT: // A <u B implies A == B is false.
>> + case ICMP_SGT: // A >s B implies A == B is false.
>> + case ICMP_SLT: // A <s B implies A == B is false.
>> + return Pred2 == ICMP_EQ;
>> + }
>> + return false;
>> +}
>>
>> //===----------------------------------------------------------------------===//
>> // SwitchInst Implementation
>>
>>
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