diff options
Diffstat (limited to 'lib/Transforms')
| -rw-r--r-- | lib/Transforms/Scalar/GVN.cpp | 44 |
1 files changed, 26 insertions, 18 deletions
diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index e878050364..72eb9002ce 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -1425,32 +1425,40 @@ bool GVN::processNonLocalLoad(LoadInst *LI, assert(UnavailablePred != 0 && "Fully available value should be eliminated above!"); + // We don't currently handle critical edges :( + if (UnavailablePred->getTerminator()->getNumSuccessors() != 1) { + DEBUG(errs() << "COULD NOT PRE LOAD BECAUSE OF CRITICAL EDGE '" + << UnavailablePred->getName() << "': " << *LI << '\n'); + return false; + } + // If the loaded pointer is PHI node defined in this block, do PHI translation // to get its value in the predecessor. Value *LoadPtr = MD->PHITranslatePointer(LI->getOperand(0), LoadBB, UnavailablePred, TD); + // Make sure the value is live in the predecessor. MemDep found a computation + // of LPInst with the right value, but that does not dominate UnavailablePred, + // then we can't use it. + if (Instruction *LPInst = dyn_cast_or_null<Instruction>(LoadPtr)) + if (!DT->dominates(LPInst->getParent(), UnavailablePred)) + LoadPtr = 0; + + // If we don't have a computation of this phi translated value, try to insert + // one. if (LoadPtr == 0) { - DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR CAN'T BE PHI TRANSLATED: " - << *LI->getOperand(0) << '\n' << *LI << "\n"); - return false; - } - - // Make sure the value is live in the predecessor. If it was defined by a - // non-PHI instruction in this block, we don't know how to recompute it above. - if (Instruction *LPInst = dyn_cast<Instruction>(LoadPtr)) - if (!DT->dominates(LPInst->getParent(), UnavailablePred)) { - DEBUG(errs() << "COULDN'T PRE LOAD BECAUSE PTR DOES NOT DOMINATE PRED: " - << *LPInst << '\n' << *LI << "\n"); + LoadPtr = MD->InsertPHITranslatedPointer(LI->getOperand(0), + LoadBB, UnavailablePred, TD); + if (LoadPtr == 0) { + DEBUG(errs() << "COULDN'T INSERT PHI TRANSLATED VALUE OF: " + << *LI->getOperand(0) << "\n"); return false; } - - // We don't currently handle critical edges :( - if (UnavailablePred->getTerminator()->getNumSuccessors() != 1) { - DEBUG(errs() << "COULD NOT PRE LOAD BECAUSE OF CRITICAL EDGE '" - << UnavailablePred->getName() << "': " << *LI << '\n'); - return false; + + // FIXME: This inserts a computation, but we don't tell scalar GVN + // optimization stuff about it. How do we do this? + DEBUG(errs() << "INSERTED PHI TRANSLATED VALUE: " << *LoadPtr << "\n"); } - + // Make sure it is valid to move this load here. We have to watch out for: // @1 = getelementptr (i8* p, ... // test p and branch if == 0 |