Index: lib/Transforms/Utils/SimplifyCFG.cpp =================================================================== --- lib/Transforms/Utils/SimplifyCFG.cpp +++ lib/Transforms/Utils/SimplifyCFG.cpp @@ -3217,26 +3217,94 @@ // exception then zap the landing pad, turning its invokes into calls. BasicBlock *BB = RI->getParent(); LandingPadInst *LPInst = dyn_cast(BB->getFirstNonPHI()); - if (RI->getValue() != LPInst) - // Not a landing pad, or the resume is not unwinding the exception that - // caused control to branch here. + + // If RI->getValue() is a landing pad, check if the first instruction is + // the same landing pad that caused control to branch here. If RI->getValue + // is a phi of landing pad, check its predecessor blocks to see if any of + // them contains a trivial landing pad. + if (RI->getValue() != LPInst && !isa(RI->getValue())) return false; - // Check that there are no other instructions except for debug intrinsics. - BasicBlock::iterator I = LPInst->getIterator(), E = RI->getIterator(); + // Check that there are no other instructions except for debug intrinsics + // between the landing pad (or phi of landing pad) and resume instruction. + BasicBlock::iterator I = cast(RI->getValue()), E = RI; while (++I != E) if (!isa(I)) return false; + SmallSet TrivialUnwindBlocks; + auto *PhiLPInst = dyn_cast(RI->getValue()); + if (!PhiLPInst) { + // Landing pad is in current block, which has already been checked. + TrivialUnwindBlocks.insert(BB); + } else { + // Check incoming blocks to see if any of them are trivial. + for (unsigned Idx = 0, End = PhiLPInst->getNumIncomingValues(); + Idx != End; Idx++) { + auto *IncomingBB = PhiLPInst->getIncomingBlock(Idx); + auto *IncomingValue = PhiLPInst->getIncomingValue(Idx); + + // If the block has other successors, we can not delete it because + // it has other dependents. + if (IncomingBB->getUniqueSuccessor() != BB) + continue; + + auto *LandingPad = + dyn_cast(IncomingBB->getFirstNonPHI()); + // Not the landing pad that caused the control to branch here. + if (IncomingValue != LandingPad) + continue; + + bool isTrivial = true; + + I = IncomingBB->getFirstNonPHI(); + E = IncomingBB->getTerminator(); + while (++I != E) + if (!isa(I)) { + isTrivial = false; + break; + } + + if (isTrivial) + TrivialUnwindBlocks.insert(IncomingBB); + } + } + // Turn all invokes that unwind here into calls and delete the basic block. - for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE;) { - BasicBlock *Pred = *PI++; - removeUnwindEdge(Pred); + for (auto *TrivialBB : TrivialUnwindBlocks) { + // Blocks that will be deleted should also be removed from the phi node. + // Note there could be multiple edges to the resume block, and we need + // to remove them all. + while (PhiLPInst && PhiLPInst->getBasicBlockIndex(TrivialBB) != -1) { + BB->removePredecessor(TrivialBB, true); + } + + for (pred_iterator PI = pred_begin(TrivialBB), PE = pred_end(TrivialBB); + PI != PE;) { + BasicBlock *Pred = *PI++; + removeUnwindEdge(Pred); + } + + // If TrivialBB is the resume block and is unreachable, zap it. In each + // SimplifyCFG run, only the current processed block can be erased. + // Otherwise, it will break the iteration of SimplifyCFG pass. + if (TrivialBB == BB) { + BB = nullptr; + TrivialBB->eraseFromParent(); + } else { + // Remove the branch to the resume block so that we can later + // erase the resume block. + TrivialBB->getTerminator()->eraseFromParent(); + new UnreachableInst(RI->getContext(), TrivialBB); + } } - // The landingpad is now unreachable. Zap it. - BB->eraseFromParent(); - return true; + // Delete the resume block if all its predecessors have been removed, and we + // haven't already deleted it above when deleting the landing pad blocks. + if (BB && pred_empty(BB)) + BB->eraseFromParent(); + + return !TrivialUnwindBlocks.empty(); } bool SimplifyCFGOpt::SimplifyCleanupReturn(CleanupReturnInst *RI) { Index: test/Transforms/SimplifyCFG/bug-25299.ll =================================================================== --- test/Transforms/SimplifyCFG/bug-25299.ll +++ test/Transforms/SimplifyCFG/bug-25299.ll @@ -0,0 +1,40 @@ +; RUN: opt < %s -simplifycfg -S | FileCheck %s + +;; Test case for bug 25299, contributed by David Majnemer. + +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + +define void @f(i1 %B) personality i1 undef { +entry: +;CHECK: entry +;CHECK-NEXT: call void @g() + invoke void @g() + to label %continue unwind label %unwind + +unwind: ; preds = %entry + %tmp101 = landingpad { i8*, i32 } + cleanup + br i1 %B, label %resume, label %then + +then: ; preds = %cleanup1 + br label %resume + +resume: ; preds = %cleanup2, %then, %cleanup1, %unwind + %tmp104 = phi { i8*, i32 } [ %tmp101, %then ], [ %tmp106, %cleanup2 ], [ %tmp101, %unwind ] +;CHECK-NOT: resume { i8*, i32 } %tmp104 + resume { i8*, i32 } %tmp104 + +continue: ; preds = %entry, %continue +;CHECK: continue: ; preds = %entry, %continue +;CHECK-NEXT: call void @g() + invoke void @g() + to label %continue unwind label %cleanup2 + +cleanup2: ; preds = %continue + %tmp106 = landingpad { i8*, i32 } + cleanup + br label %resume +} + +declare void @g() \ No newline at end of file Index: test/Transforms/SimplifyCFG/invoke_unwind.ll =================================================================== --- test/Transforms/SimplifyCFG/invoke_unwind.ll +++ test/Transforms/SimplifyCFG/invoke_unwind.ll @@ -17,4 +17,46 @@ resume { i8*, i32 } %exn } +declare i64 @dummy1() +declare i64 @dummy2() + +; This testcase checks to see if simplifycfg pass can convert two invoke +; instructions to call instructions if they share a common trivial unwind +; block. +define i64 @test2(i1 %cond) personality i32 (...)* @__gxx_personality_v0 { +entry: +; CHECK-LABEL: @test2( +; CHECK: %call1 = call i64 @dummy1() +; CHECK: %call2 = call i64 @dummy2() +; CHECK-NOT: resume { i8*, i32 } %lp + br i1 %cond, label %br1, label %br2 + +br1: + %call1 = invoke i64 @dummy1() + to label %invoke.cont unwind label %lpad1 + +br2: + %call2 = invoke i64 @dummy2() + to label %invoke.cont unwind label %lpad2 + +invoke.cont: + %c = phi i64 [%call1, %br1], [%call2, %br2] + ret i64 %c + + +lpad1: + %0 = landingpad { i8*, i32 } + cleanup + br label %rethrow + +rethrow: + %lp = phi { i8*, i32 } [%0, %lpad1], [%1, %lpad2] + resume { i8*, i32 } %lp + +lpad2: + %1 = landingpad { i8*, i32 } + cleanup + br label %rethrow +} + declare i32 @__gxx_personality_v0(...)