From: Peter Collingbourne <peter@pcc.me.uk>
Date: Wed, 6 Aug 2014 00:33:40 +0000 (+0000)
Subject: [dfsan] Try not to create too many additional basic blocks in functions which
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=commitdiff_plain;h=95d1d442c99dd041ec1793d7a8297b5f05dfc406

[dfsan] Try not to create too many additional basic blocks in functions which
already have a large number of blocks. Works around a performance issue with
the greedy register allocator.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214944 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp b/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
index aa68ff59b4b..3e11efc0e30 100644
--- a/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ b/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -234,6 +234,7 @@ class DataFlowSanitizer : public ModulePass {
   FunctionType *DFSanSetLabelFnTy;
   FunctionType *DFSanNonzeroLabelFnTy;
   Constant *DFSanUnionFn;
+  Constant *DFSanCheckedUnionFn;
   Constant *DFSanUnionLoadFn;
   Constant *DFSanUnimplementedFn;
   Constant *DFSanSetLabelFn;
@@ -280,6 +281,7 @@ struct DFSanFunction {
   std::vector<std::pair<PHINode *, PHINode *> > PHIFixups;
   DenseSet<Instruction *> SkipInsts;
   DenseSet<Value *> NonZeroChecks;
+  bool AvoidNewBlocks;
 
   struct CachedCombinedShadow {
     BasicBlock *Block;
@@ -294,6 +296,9 @@ struct DFSanFunction {
         IsNativeABI(IsNativeABI), ArgTLSPtr(nullptr), RetvalTLSPtr(nullptr),
         LabelReturnAlloca(nullptr) {
     DT.recalculate(*F);
+    // FIXME: Need to track down the register allocator issue which causes poor
+    // performance in pathological cases with large numbers of basic blocks.
+    AvoidNewBlocks = F->size() > 1000;
   }
   Value *getArgTLSPtr();
   Value *getArgTLS(unsigned Index, Instruction *Pos);
@@ -577,6 +582,15 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
 
   DFSanUnionFn = Mod->getOrInsertFunction("__dfsan_union", DFSanUnionFnTy);
   if (Function *F = dyn_cast<Function>(DFSanUnionFn)) {
+    F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
+    F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
+    F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
+    F->addAttribute(1, Attribute::ZExt);
+    F->addAttribute(2, Attribute::ZExt);
+  }
+  DFSanCheckedUnionFn = Mod->getOrInsertFunction("dfsan_union", DFSanUnionFnTy);
+  if (Function *F = dyn_cast<Function>(DFSanCheckedUnionFn)) {
+    F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
     F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadNone);
     F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
     F->addAttribute(1, Attribute::ZExt);
@@ -585,6 +599,7 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
   DFSanUnionLoadFn =
       Mod->getOrInsertFunction("__dfsan_union_load", DFSanUnionLoadFnTy);
   if (Function *F = dyn_cast<Function>(DFSanUnionLoadFn)) {
+    F->addAttribute(AttributeSet::FunctionIndex, Attribute::NoUnwind);
     F->addAttribute(AttributeSet::FunctionIndex, Attribute::ReadOnly);
     F->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
   }
@@ -603,6 +618,7 @@ bool DataFlowSanitizer::runOnModule(Module &M) {
   for (Module::iterator i = M.begin(), e = M.end(); i != e; ++i) {
     if (!i->isIntrinsic() &&
         i != DFSanUnionFn &&
+        i != DFSanCheckedUnionFn &&
         i != DFSanUnionLoadFn &&
         i != DFSanUnimplementedFn &&
         i != DFSanSetLabelFn &&
@@ -922,23 +938,33 @@ Value *DFSanFunction::combineShadows(Value *V1, Value *V2, Instruction *Pos) {
     return CCS.Shadow;
 
   IRBuilder<> IRB(Pos);
-  BasicBlock *Head = Pos->getParent();
-  Value *Ne = IRB.CreateICmpNE(V1, V2);
-  BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
-      Ne, Pos, /*Unreachable=*/false, DFS.ColdCallWeights, &DT));
-  IRBuilder<> ThenIRB(BI);
-  CallInst *Call = ThenIRB.CreateCall2(DFS.DFSanUnionFn, V1, V2);
-  Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
-  Call->addAttribute(1, Attribute::ZExt);
-  Call->addAttribute(2, Attribute::ZExt);
-
-  BasicBlock *Tail = BI->getSuccessor(0);
-  PHINode *Phi = PHINode::Create(DFS.ShadowTy, 2, "", Tail->begin());
-  Phi->addIncoming(Call, Call->getParent());
-  Phi->addIncoming(V1, Head);
-
-  CCS.Block = Tail;
-  CCS.Shadow = Phi;
+  if (AvoidNewBlocks) {
+    CallInst *Call = IRB.CreateCall2(DFS.DFSanCheckedUnionFn, V1, V2);
+    Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
+    Call->addAttribute(1, Attribute::ZExt);
+    Call->addAttribute(2, Attribute::ZExt);
+
+    CCS.Block = Pos->getParent();
+    CCS.Shadow = Call;
+  } else {
+    BasicBlock *Head = Pos->getParent();
+    Value *Ne = IRB.CreateICmpNE(V1, V2);
+    BranchInst *BI = cast<BranchInst>(SplitBlockAndInsertIfThen(
+        Ne, Pos, /*Unreachable=*/false, DFS.ColdCallWeights, &DT));
+    IRBuilder<> ThenIRB(BI);
+    CallInst *Call = ThenIRB.CreateCall2(DFS.DFSanUnionFn, V1, V2);
+    Call->addAttribute(AttributeSet::ReturnIndex, Attribute::ZExt);
+    Call->addAttribute(1, Attribute::ZExt);
+    Call->addAttribute(2, Attribute::ZExt);
+
+    BasicBlock *Tail = BI->getSuccessor(0);
+    PHINode *Phi = PHINode::Create(DFS.ShadowTy, 2, "", Tail->begin());
+    Phi->addIncoming(Call, Call->getParent());
+    Phi->addIncoming(V1, Head);
+
+    CCS.Block = Tail;
+    CCS.Shadow = Phi;
+  }
 
   std::set<Value *> UnionElems;
   if (V1Elems != ShadowElements.end()) {
@@ -951,9 +977,9 @@ Value *DFSanFunction::combineShadows(Value *V1, Value *V2, Instruction *Pos) {
   } else {
     UnionElems.insert(V2);
   }
-  ShadowElements[Phi] = std::move(UnionElems);
+  ShadowElements[CCS.Shadow] = std::move(UnionElems);
 
-  return Phi;
+  return CCS.Shadow;
 }
 
 // A convenience function which folds the shadows of each of the operands
@@ -1022,7 +1048,7 @@ Value *DFSanFunction::loadShadow(Value *Addr, uint64_t Size, uint64_t Align,
                           IRB.CreateAlignedLoad(ShadowAddr1, ShadowAlign), Pos);
   }
   }
-  if (Size % (64 / DFS.ShadowWidth) == 0) {
+  if (!AvoidNewBlocks && Size % (64 / DFS.ShadowWidth) == 0) {
     // Fast path for the common case where each byte has identical shadow: load
     // shadow 64 bits at a time, fall out to a __dfsan_union_load call if any
     // shadow is non-equal.
diff --git a/test/Instrumentation/DataFlowSanitizer/union-large.ll b/test/Instrumentation/DataFlowSanitizer/union-large.ll
new file mode 100644
index 00000000000..a388f73a995
--- /dev/null
+++ b/test/Instrumentation/DataFlowSanitizer/union-large.ll
@@ -0,0 +1,3013 @@
+; RUN: opt < %s -dfsan -S | FileCheck %s
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+; Check that we use dfsan_union in large functions instead of __dfsan_union.
+
+; CHECK-LABEL: @"dfs$foo"
+define i32 @foo(i32 %a, i32 %b) {
+bb0:
+  br label %bb1
+
+bb1:
+  br label %bb2
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+  br label %bb3
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+  br label %bb755
+
+bb755:
+  br label %bb756
+
+bb756:
+  br label %bb757
+
+bb757:
+  br label %bb758
+
+bb758:
+  br label %bb759
+
+bb759:
+  br label %bb760
+
+bb760:
+  br label %bb761
+
+bb761:
+  br label %bb762
+
+bb762:
+  br label %bb763
+
+bb763:
+  br label %bb764
+
+bb764:
+  br label %bb765
+
+bb765:
+  br label %bb766
+
+bb766:
+  br label %bb767
+
+bb767:
+  br label %bb768
+
+bb768:
+  br label %bb769
+
+bb769:
+  br label %bb770
+
+bb770:
+  br label %bb771
+
+bb771:
+  br label %bb772
+
+bb772:
+  br label %bb773
+
+bb773:
+  br label %bb774
+
+bb774:
+  br label %bb775
+
+bb775:
+  br label %bb776
+
+bb776:
+  br label %bb777
+
+bb777:
+  br label %bb778
+
+bb778:
+  br label %bb779
+
+bb779:
+  br label %bb780
+
+bb780:
+  br label %bb781
+
+bb781:
+  br label %bb782
+
+bb782:
+  br label %bb783
+
+bb783:
+  br label %bb784
+
+bb784:
+  br label %bb785
+
+bb785:
+  br label %bb786
+
+bb786:
+  br label %bb787
+
+bb787:
+  br label %bb788
+
+bb788:
+  br label %bb789
+
+bb789:
+  br label %bb790
+
+bb790:
+  br label %bb791
+
+bb791:
+  br label %bb792
+
+bb792:
+  br label %bb793
+
+bb793:
+  br label %bb794
+
+bb794:
+  br label %bb795
+
+bb795:
+  br label %bb796
+
+bb796:
+  br label %bb797
+
+bb797:
+  br label %bb798
+
+bb798:
+  br label %bb799
+
+bb799:
+  br label %bb800
+
+bb800:
+  br label %bb801
+
+bb801:
+  br label %bb802
+
+bb802:
+  br label %bb803
+
+bb803:
+  br label %bb804
+
+bb804:
+  br label %bb805
+
+bb805:
+  br label %bb806
+
+bb806:
+  br label %bb807
+
+bb807:
+  br label %bb808
+
+bb808:
+  br label %bb809
+
+bb809:
+  br label %bb810
+
+bb810:
+  br label %bb811
+
+bb811:
+  br label %bb812
+
+bb812:
+  br label %bb813
+
+bb813:
+  br label %bb814
+
+bb814:
+  br label %bb815
+
+bb815:
+  br label %bb816
+
+bb816:
+  br label %bb817
+
+bb817:
+  br label %bb818
+
+bb818:
+  br label %bb819
+
+bb819:
+  br label %bb820
+
+bb820:
+  br label %bb821
+
+bb821:
+  br label %bb822
+
+bb822:
+  br label %bb823
+
+bb823:
+  br label %bb824
+
+bb824:
+  br label %bb825
+
+bb825:
+  br label %bb826
+
+bb826:
+  br label %bb827
+
+bb827:
+  br label %bb828
+
+bb828:
+  br label %bb829
+
+bb829:
+  br label %bb830
+
+bb830:
+  br label %bb831
+
+bb831:
+  br label %bb832
+
+bb832:
+  br label %bb833
+
+bb833:
+  br label %bb834
+
+bb834:
+  br label %bb835
+
+bb835:
+  br label %bb836
+
+bb836:
+  br label %bb837
+
+bb837:
+  br label %bb838
+
+bb838:
+  br label %bb839
+
+bb839:
+  br label %bb840
+
+bb840:
+  br label %bb841
+
+bb841:
+  br label %bb842
+
+bb842:
+  br label %bb843
+
+bb843:
+  br label %bb844
+
+bb844:
+  br label %bb845
+
+bb845:
+  br label %bb846
+
+bb846:
+  br label %bb847
+
+bb847:
+  br label %bb848
+
+bb848:
+  br label %bb849
+
+bb849:
+  br label %bb850
+
+bb850:
+  br label %bb851
+
+bb851:
+  br label %bb852
+
+bb852:
+  br label %bb853
+
+bb853:
+  br label %bb854
+
+bb854:
+  br label %bb855
+
+bb855:
+  br label %bb856
+
+bb856:
+  br label %bb857
+
+bb857:
+  br label %bb858
+
+bb858:
+  br label %bb859
+
+bb859:
+  br label %bb860
+
+bb860:
+  br label %bb861
+
+bb861:
+  br label %bb862
+
+bb862:
+  br label %bb863
+
+bb863:
+  br label %bb864
+
+bb864:
+  br label %bb865
+
+bb865:
+  br label %bb866
+
+bb866:
+  br label %bb867
+
+bb867:
+  br label %bb868
+
+bb868:
+  br label %bb869
+
+bb869:
+  br label %bb870
+
+bb870:
+  br label %bb871
+
+bb871:
+  br label %bb872
+
+bb872:
+  br label %bb873
+
+bb873:
+  br label %bb874
+
+bb874:
+  br label %bb875
+
+bb875:
+  br label %bb876
+
+bb876:
+  br label %bb877
+
+bb877:
+  br label %bb878
+
+bb878:
+  br label %bb879
+
+bb879:
+  br label %bb880
+
+bb880:
+  br label %bb881
+
+bb881:
+  br label %bb882
+
+bb882:
+  br label %bb883
+
+bb883:
+  br label %bb884
+
+bb884:
+  br label %bb885
+
+bb885:
+  br label %bb886
+
+bb886:
+  br label %bb887
+
+bb887:
+  br label %bb888
+
+bb888:
+  br label %bb889
+
+bb889:
+  br label %bb890
+
+bb890:
+  br label %bb891
+
+bb891:
+  br label %bb892
+
+bb892:
+  br label %bb893
+
+bb893:
+  br label %bb894
+
+bb894:
+  br label %bb895
+
+bb895:
+  br label %bb896
+
+bb896:
+  br label %bb897
+
+bb897:
+  br label %bb898
+
+bb898:
+  br label %bb899
+
+bb899:
+  br label %bb900
+
+bb900:
+  br label %bb901
+
+bb901:
+  br label %bb902
+
+bb902:
+  br label %bb903
+
+bb903:
+  br label %bb904
+
+bb904:
+  br label %bb905
+
+bb905:
+  br label %bb906
+
+bb906:
+  br label %bb907
+
+bb907:
+  br label %bb908
+
+bb908:
+  br label %bb909
+
+bb909:
+  br label %bb910
+
+bb910:
+  br label %bb911
+
+bb911:
+  br label %bb912
+
+bb912:
+  br label %bb913
+
+bb913:
+  br label %bb914
+
+bb914:
+  br label %bb915
+
+bb915:
+  br label %bb916
+
+bb916:
+  br label %bb917
+
+bb917:
+  br label %bb918
+
+bb918:
+  br label %bb919
+
+bb919:
+  br label %bb920
+
+bb920:
+  br label %bb921
+
+bb921:
+  br label %bb922
+
+bb922:
+  br label %bb923
+
+bb923:
+  br label %bb924
+
+bb924:
+  br label %bb925
+
+bb925:
+  br label %bb926
+
+bb926:
+  br label %bb927
+
+bb927:
+  br label %bb928
+
+bb928:
+  br label %bb929
+
+bb929:
+  br label %bb930
+
+bb930:
+  br label %bb931
+
+bb931:
+  br label %bb932
+
+bb932:
+  br label %bb933
+
+bb933:
+  br label %bb934
+
+bb934:
+  br label %bb935
+
+bb935:
+  br label %bb936
+
+bb936:
+  br label %bb937
+
+bb937:
+  br label %bb938
+
+bb938:
+  br label %bb939
+
+bb939:
+  br label %bb940
+
+bb940:
+  br label %bb941
+
+bb941:
+  br label %bb942
+
+bb942:
+  br label %bb943
+
+bb943:
+  br label %bb944
+
+bb944:
+  br label %bb945
+
+bb945:
+  br label %bb946
+
+bb946:
+  br label %bb947
+
+bb947:
+  br label %bb948
+
+bb948:
+  br label %bb949
+
+bb949:
+  br label %bb950
+
+bb950:
+  br label %bb951
+
+bb951:
+  br label %bb952
+
+bb952:
+  br label %bb953
+
+bb953:
+  br label %bb954
+
+bb954:
+  br label %bb955
+
+bb955:
+  br label %bb956
+
+bb956:
+  br label %bb957
+
+bb957:
+  br label %bb958
+
+bb958:
+  br label %bb959
+
+bb959:
+  br label %bb960
+
+bb960:
+  br label %bb961
+
+bb961:
+  br label %bb962
+
+bb962:
+  br label %bb963
+
+bb963:
+  br label %bb964
+
+bb964:
+  br label %bb965
+
+bb965:
+  br label %bb966
+
+bb966:
+  br label %bb967
+
+bb967:
+  br label %bb968
+
+bb968:
+  br label %bb969
+
+bb969:
+  br label %bb970
+
+bb970:
+  br label %bb971
+
+bb971:
+  br label %bb972
+
+bb972:
+  br label %bb973
+
+bb973:
+  br label %bb974
+
+bb974:
+  br label %bb975
+
+bb975:
+  br label %bb976
+
+bb976:
+  br label %bb977
+
+bb977:
+  br label %bb978
+
+bb978:
+  br label %bb979
+
+bb979:
+  br label %bb980
+
+bb980:
+  br label %bb981
+
+bb981:
+  br label %bb982
+
+bb982:
+  br label %bb983
+
+bb983:
+  br label %bb984
+
+bb984:
+  br label %bb985
+
+bb985:
+  br label %bb986
+
+bb986:
+  br label %bb987
+
+bb987:
+  br label %bb988
+
+bb988:
+  br label %bb989
+
+bb989:
+  br label %bb990
+
+bb990:
+  br label %bb991
+
+bb991:
+  br label %bb992
+
+bb992:
+  br label %bb993
+
+bb993:
+  br label %bb994
+
+bb994:
+  br label %bb995
+
+bb995:
+  br label %bb996
+
+bb996:
+  br label %bb997
+
+bb997:
+  br label %bb998
+
+bb998:
+  br label %bb999
+
+bb999:
+  br label %bb1000
+
+bb1000:
+  ; CHECK: call{{.*}}@dfsan_union
+  ; CHECK-NOT: phi
+  %ab = mul i32 %a, %b
+  ret i32 %ab
+}