All libcalls should be considered to be GC-leaf functions.

Summary:
It is possible for some passes to materialize a call to a libcall (ex: ldexp, exp2, etc),
but these passes will not mark the call as a gc-leaf-function. All libcalls are
actually gc-leaf-functions, so we change llvm::callsGCLeafFunction() to tell us that
available libcalls are equivalent to gc-leaf-function calls.

Reviewers: sanjoy, anna, reames

Reviewed By: anna

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D35840

llvm-svn: 309291

3 files changed, 36 insertions, 12 deletions

diff --git a/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp b/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp
index e47b636348e..2d0cb6fbf21 100644
--- a/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp
+++ b/llvm/lib/Transforms/Scalar/PlaceSafepoints.cpp
@@ -54,6 +54,7 @@
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/CFG.h"
 #include "llvm/Analysis/ScalarEvolution.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Dominators.h"
 #include "llvm/IR/IntrinsicInst.h"
@@ -113,6 +114,7 @@ struct PlaceBackedgeSafepointsImpl : public FunctionPass {
   ScalarEvolution *SE = nullptr;
   DominatorTree *DT = nullptr;
   LoopInfo *LI = nullptr;
+  TargetLibraryInfo *TLI = nullptr;
 
   PlaceBackedgeSafepointsImpl(bool CallSafepoints = false)
       : FunctionPass(ID), CallSafepointsEnabled(CallSafepoints) {
@@ -131,6 +133,7 @@ struct PlaceBackedgeSafepointsImpl : public FunctionPass {
     SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
     DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
     LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+    TLI = &getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
     for (Loop *I : *LI) {
       runOnLoopAndSubLoops(I);
     }
@@ -141,6 +144,7 @@ struct PlaceBackedgeSafepointsImpl : public FunctionPass {
     AU.addRequired<DominatorTreeWrapperPass>();
     AU.addRequired<ScalarEvolutionWrapperPass>();
     AU.addRequired<LoopInfoWrapperPass>();
+    AU.addRequired<TargetLibraryInfoWrapperPass>();
     // We no longer modify the IR at all in this pass.  Thus all
     // analysis are preserved.
     AU.setPreservesAll();
@@ -165,6 +169,7 @@ struct PlaceSafepoints : public FunctionPass {
     // We modify the graph wholesale (inlining, block insertion, etc).  We
     // preserve nothing at the moment.  We could potentially preserve dom tree
     // if that was worth doing
+    AU.addRequired<TargetLibraryInfoWrapperPass>();
   }
 };
 }
@@ -174,10 +179,11 @@ struct PlaceSafepoints : public FunctionPass {
 // callers job.
 static void
 InsertSafepointPoll(Instruction *InsertBefore,
-                    std::vector<CallSite> &ParsePointsNeeded /*rval*/);
+                    std::vector<CallSite> &ParsePointsNeeded /*rval*/,
+                    const TargetLibraryInfo &TLI);
 
-static bool needsStatepoint(const CallSite &CS) {
-  if (callsGCLeafFunction(CS))
+static bool needsStatepoint(const CallSite &CS, const TargetLibraryInfo &TLI) {
+  if (callsGCLeafFunction(CS, TLI))
     return false;
   if (CS.isCall()) {
     CallInst *call = cast<CallInst>(CS.getInstruction());
@@ -194,7 +200,8 @@ static bool needsStatepoint(const CallSite &CS) {
 /// answer; i.e. false is always valid.
 static bool containsUnconditionalCallSafepoint(Loop *L, BasicBlock *Header,
                                                BasicBlock *Pred,
-                                               DominatorTree &DT) {
+                                               DominatorTree &DT,
+                                               const TargetLibraryInfo &TLI) {
   // In general, we're looking for any cut of the graph which ensures
   // there's a call safepoint along every edge between Header and Pred.
   // For the moment, we look only for the 'cuts' that consist of a single call
@@ -217,7 +224,7 @@ static bool containsUnconditionalCallSafepoint(Loop *L, BasicBlock *Header,
         // unconditional poll. In practice, this is only a theoretical concern
         // since we don't have any methods with conditional-only safepoint
         // polls.
-        if (needsStatepoint(CS))
+        if (needsStatepoint(CS, TLI))
           return true;
     }
 
@@ -321,7 +328,7 @@ bool PlaceBackedgeSafepointsImpl::runOnLoop(Loop *L) {
         continue;
       }
       if (CallSafepointsEnabled &&
-          containsUnconditionalCallSafepoint(L, Header, Pred, *DT)) {
+          containsUnconditionalCallSafepoint(L, Header, Pred, *DT, *TLI)) {
         // Note: This is only semantically legal since we won't do any further
         // IPO or inlining before the actual call insertion..  If we hadn't, we
         // might latter loose this call safepoint.
@@ -472,6 +479,9 @@ bool PlaceSafepoints::runOnFunction(Function &F) {
   if (!shouldRewriteFunction(F))
     return false;
 
+  const TargetLibraryInfo &TLI =
+      getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
+
   bool Modified = false;
 
   // In various bits below, we rely on the fact that uses are reachable from
@@ -578,7 +588,7 @@ bool PlaceSafepoints::runOnFunction(Function &F) {
   // safepoint polls themselves.
   for (Instruction *PollLocation : PollsNeeded) {
     std::vector<CallSite> RuntimeCalls;
-    InsertSafepointPoll(PollLocation, RuntimeCalls);
+    InsertSafepointPoll(PollLocation, RuntimeCalls, TLI);
     ParsePointNeeded.insert(ParsePointNeeded.end(), RuntimeCalls.begin(),
                             RuntimeCalls.end());
   }
@@ -610,7 +620,8 @@ INITIALIZE_PASS_END(PlaceSafepoints, "place-safepoints", "Place Safepoints",
 
 static void
 InsertSafepointPoll(Instruction *InsertBefore,
-                    std::vector<CallSite> &ParsePointsNeeded /*rval*/) {
+                    std::vector<CallSite> &ParsePointsNeeded /*rval*/,
+                    const TargetLibraryInfo &TLI) {
   BasicBlock *OrigBB = InsertBefore->getParent();
   Module *M = InsertBefore->getModule();
   assert(M && "must be part of a module");
@@ -669,7 +680,7 @@ InsertSafepointPoll(Instruction *InsertBefore,
   assert(ParsePointsNeeded.empty());
   for (auto *CI : Calls) {
     // No safepoint needed or wanted
-    if (!needsStatepoint(CI))
+    if (!needsStatepoint(CI, TLI))
       continue;
 
     // These are likely runtime calls.  Should we assert that via calling
diff --git a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
index f19d45329d2..24489157773 100644
--- a/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
+++ b/llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp
@@ -19,6 +19,7 @@
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/CFG.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/CallSite.h"
@@ -103,6 +104,7 @@ struct RewriteStatepointsForGC : public ModulePass {
     // else.  We could in theory preserve a lot more analyses here.
     AU.addRequired<DominatorTreeWrapperPass>();
     AU.addRequired<TargetTransformInfoWrapperPass>();
+    AU.addRequired<TargetLibraryInfoWrapperPass>();
   }
 
   /// The IR fed into RewriteStatepointsForGC may have had attributes and
@@ -2419,10 +2421,12 @@ bool RewriteStatepointsForGC::runOnFunction(Function &F) {
   DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>(F).getDomTree();
   TargetTransformInfo &TTI =
       getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
+  const TargetLibraryInfo &TLI =
+      getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
 
-  auto NeedsRewrite = [](Instruction &I) {
+  auto NeedsRewrite = [&TLI](Instruction &I) {
     if (ImmutableCallSite CS = ImmutableCallSite(&I))
-      return !callsGCLeafFunction(CS) && !isStatepoint(CS);
+      return !callsGCLeafFunction(CS, TLI) && !isStatepoint(CS);
     return false;
   };
 
diff --git a/llvm/lib/Transforms/Utils/Local.cpp b/llvm/lib/Transforms/Utils/Local.cpp
index 74610613001..805d7155ec7 100644
--- a/llvm/lib/Transforms/Utils/Local.cpp
+++ b/llvm/lib/Transforms/Utils/Local.cpp
@@ -1832,7 +1832,8 @@ unsigned llvm::replaceDominatedUsesWith(Value *From, Value *To,
   return ::replaceDominatedUsesWith(From, To, BB, ProperlyDominates);
 }
 
-bool llvm::callsGCLeafFunction(ImmutableCallSite CS) {
+bool llvm::callsGCLeafFunction(ImmutableCallSite CS,
+                               const TargetLibraryInfo &TLI) {
   // Check if the function is specifically marked as a gc leaf function.
   if (CS.hasFnAttr("gc-leaf-function"))
     return true;
@@ -1846,6 +1847,14 @@ bool llvm::callsGCLeafFunction(ImmutableCallSite CS) {
              IID != Intrinsic::experimental_deoptimize;
   }
 
+  // Lib calls can be materialized by some passes, and won't be
+  // marked as 'gc-leaf-function.' All available Libcalls are
+  // GC-leaf.
+  LibFunc LF;
+  if (TLI.getLibFunc(CS, LF)) {
+    return TLI.has(LF);
+  }
+
   return false;
 }