forked from OSchip/llvm-project
2432bd0ddd
D16251) Summary: This is a simpler fix to the problem than the dominator approach in http://reviews.llvm.org/D16251. It adds only values into the gather() while loop that have been seen before. The actual endless loop is in the constant compare gather() routine in Utils/SimplifyCFG.cpp. The same value ret.0.off0.i is pushed back into the queue: %.ret.0.off0.i = or i1 %.ret.0.off0.i, %cmp10.i Here is what happens at the IR level: for.cond.i: ; preds = %if.end6.i, %if.end.i54 %ix.0.i = phi i32 [ 0, %if.end.i54 ], [ %inc.i55, %if.end6.i ] %ret.0.off0.i = phi i1 [false, %if.end.i54], [%.ret.0.off0.i, %if.end6.i] <<< %cmp2.i = icmp ult i32 %ix.0.i, %11 br i1 %cmp2.i, label %for.body.i, label %LBJ_TmpSimpleNeedExt.exit if.end6.i: ; preds = %for.body.i %cmp10.i = icmp ugt i32 %conv.i, %add9.i %.ret.0.off0.i = or i1 %ret.0.off0.i, %cmp10.i <<< When if.end.i54 gets eliminated which removes the definition of ret.0.off0.i. The result is the expression %.ret.0.off0.i = or i1 %.ret.0.off0.i, %cmp10.i (Note the first ‘or’ operand is now %.ret.0.off0.i, and *NOT* %ret.0.off0.i). And now there is use of .ret.0.off0.i before a definition which triggers the “endless” loop in gather(): while(!DFT.empty()) { V = DFT.pop_back_val(); // V is .ret.0.off0.i if (Instruction *I = dyn_cast<Instruction>(V)) { // If it is a || (or && depending on isEQ), process the operands. if (I->getOpcode() == (isEQ ? Instruction::Or : Instruction::And)) { DFT.push_back(I->getOperand(1)); // This is now .ret.0.off0.i also DFT.push_back(I->getOperand(0)); continue; // “endless loop” for .ret.0.off0.i } Reviewers: reames, ahatanak Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D16839 llvm-svn: 259730 |
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| .. | ||
| ASanStackFrameLayout.cpp | ||
| AddDiscriminators.cpp | ||
| BasicBlockUtils.cpp | ||
| BreakCriticalEdges.cpp | ||
| BuildLibCalls.cpp | ||
| BypassSlowDivision.cpp | ||
| CMakeLists.txt | ||
| CloneFunction.cpp | ||
| CloneModule.cpp | ||
| CmpInstAnalysis.cpp | ||
| CodeExtractor.cpp | ||
| CtorUtils.cpp | ||
| DemoteRegToStack.cpp | ||
| Evaluator.cpp | ||
| FlattenCFG.cpp | ||
| GlobalStatus.cpp | ||
| InlineFunction.cpp | ||
| InstructionNamer.cpp | ||
| IntegerDivision.cpp | ||
| LCSSA.cpp | ||
| LLVMBuild.txt | ||
| Local.cpp | ||
| LoopSimplify.cpp | ||
| LoopUnroll.cpp | ||
| LoopUnrollRuntime.cpp | ||
| LoopUtils.cpp | ||
| LoopVersioning.cpp | ||
| LowerInvoke.cpp | ||
| LowerSwitch.cpp | ||
| Mem2Reg.cpp | ||
| MemorySSA.cpp | ||
| MetaRenamer.cpp | ||
| ModuleUtils.cpp | ||
| PromoteMemoryToRegister.cpp | ||
| SSAUpdater.cpp | ||
| SanitizerStats.cpp | ||
| SimplifyCFG.cpp | ||
| SimplifyIndVar.cpp | ||
| SimplifyInstructions.cpp | ||
| SimplifyLibCalls.cpp | ||
| SplitModule.cpp | ||
| SymbolRewriter.cpp | ||
| UnifyFunctionExitNodes.cpp | ||
| Utils.cpp | ||
| ValueMapper.cpp | ||