diff options
author | Tom Stellard <tstellar@redhat.com> | 2018-04-11 22:38:11 +0000 |
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committer | Tom Stellard <tstellar@redhat.com> | 2018-04-11 22:38:11 +0000 |
commit | 7ce61db5caa6858bfa40fd33bcbc44b9123a39cf (patch) | |
tree | 99add482e22a11c1a5d702912a01b1a7863e9abd /lib/Transforms | |
parent | 84bc444011dcc51cac4d95503495fa35f4f4032a (diff) |
Merging r326404:
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r326404 | rnk | 2018-02-28 17:19:18 -0800 (Wed, 28 Feb 2018) | 14 lines
[IPSCCP] do not break musttail invariant (PR36485)
Do not replace results of `musttail` calls with a constant if the
call itself can't be removed.
Do not zap returns of `musttail` callees, if the call site can't be
removed and replaced with a constant.
Do not zap returns of `musttail`-calling blocks, this breaks
invariant too.
Patch by Fedor Indutny
Differential Revision: https://reviews.llvm.org/D43695
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_60@329855 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/Transforms')
-rw-r--r-- | lib/Transforms/Scalar/SCCP.cpp | 56 |
1 files changed, 55 insertions, 1 deletions
diff --git a/lib/Transforms/Scalar/SCCP.cpp b/lib/Transforms/Scalar/SCCP.cpp index 9dc550ceaec..69636ed3ac8 100644 --- a/lib/Transforms/Scalar/SCCP.cpp +++ b/lib/Transforms/Scalar/SCCP.cpp @@ -223,6 +223,10 @@ class SCCPSolver : public InstVisitor<SCCPSolver> { /// represented here for efficient lookup. SmallPtrSet<Function *, 16> MRVFunctionsTracked; + /// MustTailFunctions - Each function here is a callee of non-removable + /// musttail call site. + SmallPtrSet<Function *, 16> MustTailCallees; + /// TrackingIncomingArguments - This is the set of functions for whose /// arguments we make optimistic assumptions about and try to prove as /// constants. @@ -289,6 +293,18 @@ public: TrackedRetVals.insert(std::make_pair(F, LatticeVal())); } + /// AddMustTailCallee - If the SCCP solver finds that this function is called + /// from non-removable musttail call site. + void AddMustTailCallee(Function *F) { + MustTailCallees.insert(F); + } + + /// Returns true if the given function is called from non-removable musttail + /// call site. + bool isMustTailCallee(Function *F) { + return MustTailCallees.count(F); + } + void AddArgumentTrackedFunction(Function *F) { TrackingIncomingArguments.insert(F); } @@ -358,6 +374,12 @@ public: return MRVFunctionsTracked; } + /// getMustTailCallees - Get the set of functions which are called + /// from non-removable musttail call sites. + const SmallPtrSet<Function *, 16> getMustTailCallees() { + return MustTailCallees; + } + /// markOverdefined - Mark the specified value overdefined. This /// works with both scalars and structs. void markOverdefined(Value *V) { @@ -1672,6 +1694,23 @@ static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) { IV.isConstant() ? IV.getConstant() : UndefValue::get(V->getType()); } assert(Const && "Constant is nullptr here!"); + + // Replacing `musttail` instructions with constant breaks `musttail` invariant + // unless the call itself can be removed + CallInst *CI = dyn_cast<CallInst>(V); + if (CI && CI->isMustTailCall() && !isInstructionTriviallyDead(CI)) { + CallSite CS(CI); + Function *F = CS.getCalledFunction(); + + // Don't zap returns of the callee + if (F) + Solver.AddMustTailCallee(F); + + DEBUG(dbgs() << " Can\'t treat the result of musttail call : " << *CI + << " as a constant\n"); + return false; + } + DEBUG(dbgs() << " Constant: " << *Const << " = " << *V << '\n'); // Replaces all of the uses of a variable with uses of the constant. @@ -1802,10 +1841,25 @@ static void findReturnsToZap(Function &F, if (!Solver.isArgumentTrackedFunction(&F)) return; - for (BasicBlock &BB : F) + // There is a non-removable musttail call site of this function. Zapping + // returns is not allowed. + if (Solver.isMustTailCallee(&F)) { + DEBUG(dbgs() << "Can't zap returns of the function : " << F.getName() + << " due to present musttail call of it\n"); + return; + } + + for (BasicBlock &BB : F) { + if (CallInst *CI = BB.getTerminatingMustTailCall()) { + DEBUG(dbgs() << "Can't zap return of the block due to present " + << "musttail call : " << *CI << "\n"); + return; + } + if (auto *RI = dyn_cast<ReturnInst>(BB.getTerminator())) if (!isa<UndefValue>(RI->getOperand(0))) ReturnsToZap.push_back(RI); + } } static bool runIPSCCP(Module &M, const DataLayout &DL, |