From 0c264b16b0e8a373888d1a5cfeb90af4fda3cd14 Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Sat, 28 Nov 2009 16:08:18 +0000 Subject: reenable load address insertion in load pre. This allows us to handle cases like this: void test(int N, double* G) { long j; for (j = 1; j < N - 1; j++) G[j+1] = G[j] + G[j+1]; } where G[1] isn't live into the loop. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@90041 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Scalar/GVN.cpp | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) (limited to 'lib') diff --git a/lib/Transforms/Scalar/GVN.cpp b/lib/Transforms/Scalar/GVN.cpp index 6311491c7d..6f1c32c004 100644 --- a/lib/Transforms/Scalar/GVN.cpp +++ b/lib/Transforms/Scalar/GVN.cpp @@ -1438,16 +1438,19 @@ bool GVN::processNonLocalLoad(LoadInst *LI, // FIXME: This may insert a computation, but we don't tell scalar GVN // optimization stuff about it. How do we do this? SmallVector NewInsts; -#if 0 - Value *LoadPtr = - MD->InsertPHITranslatedPointer(LI->getOperand(0), LoadBB, - UnavailablePred, TD, *DT, NewInsts); -#else - Value *LoadPtr = - MD->GetAvailablePHITranslatedValue(LI->getOperand(0), LoadBB, - UnavailablePred, TD, *DT); -#endif + Value *LoadPtr = 0; + // If all preds have a single successor, then we know it is safe to insert the + // load on the pred (?!?), so we can insert code to materialize the pointer if + // it is not available. + if (allSingleSucc) { + LoadPtr = MD->InsertPHITranslatedPointer(LI->getOperand(0), LoadBB, + UnavailablePred, TD, *DT,NewInsts); + } else { + LoadPtr = MD->GetAvailablePHITranslatedValue(LI->getOperand(0), LoadBB, + UnavailablePred, TD, *DT); + } + // If we couldn't find or insert a computation of this phi translated value, // we fail PRE. if (LoadPtr == 0) { @@ -1467,14 +1470,19 @@ bool GVN::processNonLocalLoad(LoadInst *LI, // put anywhere; this can be improved, but should be conservatively safe. if (!allSingleSucc && // FIXME: REEVALUTE THIS. - !isSafeToLoadUnconditionally(LoadPtr, UnavailablePred->getTerminator())) + !isSafeToLoadUnconditionally(LoadPtr, UnavailablePred->getTerminator())) { + assert(NewInsts.empty() && "Should not have inserted instructions"); return false; + } // Okay, we can eliminate this load by inserting a reload in the predecessor // and using PHI construction to get the value in the other predecessors, do // it. DEBUG(errs() << "GVN REMOVING PRE LOAD: " << *LI << '\n'); - + DEBUG(if (!NewInsts.empty()) + errs() << "INSERTED " << NewInsts.size() << " INSTS: " + << *NewInsts.back() << '\n'); + Value *NewLoad = new LoadInst(LoadPtr, LI->getName()+".pre", false, LI->getAlignment(), UnavailablePred->getTerminator()); -- cgit v1.2.3