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authorTom Stellard <tstellar@redhat.com>2018-04-11 22:38:11 +0000
committerTom Stellard <tstellar@redhat.com>2018-04-11 22:38:11 +0000
commit7ce61db5caa6858bfa40fd33bcbc44b9123a39cf (patch)
tree99add482e22a11c1a5d702912a01b1a7863e9abd
parent84bc444011dcc51cac4d95503495fa35f4f4032a (diff)
Merging r326404:
------------------------------------------------------------------------ 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 ------------------------------------------------------------------------ git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_60@329855 91177308-0d34-0410-b5e6-96231b3b80d8
-rw-r--r--lib/Transforms/Scalar/SCCP.cpp56
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,