diff options
Diffstat (limited to 'lib/IR/ConstantFold.cpp')
-rw-r--r-- | lib/IR/ConstantFold.cpp | 34 |
1 files changed, 26 insertions, 8 deletions
diff --git a/lib/IR/ConstantFold.cpp b/lib/IR/ConstantFold.cpp index 706e66f..395ac39 100644 --- a/lib/IR/ConstantFold.cpp +++ b/lib/IR/ConstantFold.cpp @@ -529,7 +529,10 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, Constant *V, // Try hard to fold cast of cast because they are often eliminable. if (unsigned newOpc = foldConstantCastPair(opc, CE, DestTy)) return ConstantExpr::getCast(newOpc, CE->getOperand(0), DestTy); - } else if (CE->getOpcode() == Instruction::GetElementPtr) { + } else if (CE->getOpcode() == Instruction::GetElementPtr && + // Do not fold addrspacecast (gep 0, .., 0). It might make the + // addrspacecast uncanonicalized. + opc != Instruction::AddrSpaceCast) { // If all of the indexes in the GEP are null values, there is no pointer // adjustment going on. We might as well cast the source pointer. bool isAllNull = true; @@ -1331,6 +1334,15 @@ static FCmpInst::Predicate evaluateFCmpRelation(Constant *V1, Constant *V2) { return FCmpInst::BAD_FCMP_PREDICATE; } +static ICmpInst::Predicate areGlobalsPotentiallyEqual(const GlobalValue *GV1, + const GlobalValue *GV2) { + // Don't try to decide equality of aliases. + if (!isa<GlobalAlias>(GV1) && !isa<GlobalAlias>(GV2)) + if (!GV1->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) + return ICmpInst::ICMP_NE; + return ICmpInst::BAD_ICMP_PREDICATE; +} + /// evaluateICmpRelation - This function determines if there is anything we can /// decide about the two constants provided. This doesn't need to handle simple /// things like integer comparisons, but should instead handle ConstantExprs @@ -1392,10 +1404,7 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, // constant (which, since the types must match, means that it's a // ConstantPointerNull). if (const GlobalValue *GV2 = dyn_cast<GlobalValue>(V2)) { - // Don't try to decide equality of aliases. - if (!isa<GlobalAlias>(GV) && !isa<GlobalAlias>(GV2)) - if (!GV->hasExternalWeakLinkage() || !GV2->hasExternalWeakLinkage()) - return ICmpInst::ICMP_NE; + return areGlobalsPotentiallyEqual(GV, GV2); } else if (isa<BlockAddress>(V2)) { return ICmpInst::ICMP_NE; // Globals never equal labels. } else { @@ -1460,7 +1469,8 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, } break; - case Instruction::GetElementPtr: + case Instruction::GetElementPtr: { + GEPOperator *CE1GEP = cast<GEPOperator>(CE1); // Ok, since this is a getelementptr, we know that the constant has a // pointer type. Check the various cases. if (isa<ConstantPointerNull>(V2)) { @@ -1507,7 +1517,8 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, "Surprising getelementptr!"); return isSigned ? ICmpInst::ICMP_SGT : ICmpInst::ICMP_UGT; } else { - // If they are different globals, we don't know what the value is. + if (CE1GEP->hasAllZeroIndices()) + return areGlobalsPotentiallyEqual(GV, GV2); return ICmpInst::BAD_ICMP_PREDICATE; } } @@ -1523,8 +1534,14 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, // By far the most common case to handle is when the base pointers are // obviously to the same global. if (isa<GlobalValue>(CE1Op0) && isa<GlobalValue>(CE2Op0)) { - if (CE1Op0 != CE2Op0) // Don't know relative ordering. + // Don't know relative ordering, but check for inequality. + if (CE1Op0 != CE2Op0) { + GEPOperator *CE2GEP = cast<GEPOperator>(CE2); + if (CE1GEP->hasAllZeroIndices() && CE2GEP->hasAllZeroIndices()) + return areGlobalsPotentiallyEqual(cast<GlobalValue>(CE1Op0), + cast<GlobalValue>(CE2Op0)); return ICmpInst::BAD_ICMP_PREDICATE; + } // Ok, we know that both getelementptr instructions are based on the // same global. From this, we can precisely determine the relative // ordering of the resultant pointers. @@ -1570,6 +1587,7 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2, } } } + } default: break; } |