[FuncSpec] Query SCCPSolver in more places

llvm/include/llvm/Transforms/IPO/FunctionSpecialization.h

@@ -176,7 +176,7 @@ class InstCostVisitor : public InstVisitor<InstCostVisitor, Constant *> {
                   SCCPSolver &Solver)
       : GetBFI(GetBFI), F(F), DL(DL), TTI(TTI), Solver(Solver) {}
 
-  bool isBlockExecutable(BasicBlock *BB) {
+  bool isBlockExecutable(BasicBlock *BB) const {
     return Solver.isBlockExecutable(BB) && !DeadBlocks.contains(BB);
   }
 
@@ -189,8 +189,9 @@ class InstCostVisitor : public InstVisitor<InstCostVisitor, Constant *> {
 private:
   friend class InstVisitor<InstCostVisitor, Constant *>;
 
-  static bool canEliminateSuccessor(BasicBlock *BB, BasicBlock *Succ,
-                                    DenseSet<BasicBlock *> &DeadBlocks);
+  Constant *findConstantFor(Value *V) const;
+
+  bool canEliminateSuccessor(BasicBlock *BB, BasicBlock *Succ) const;
 
   Cost getCodeSizeSavingsForUser(Instruction *User, Value *Use = nullptr,
                                  Constant *C = nullptr);

llvm/lib/Transforms/IPO/FunctionSpecialization.cpp

@@ -90,13 +90,12 @@ static cl::opt<bool> SpecializeLiteralConstant(
         "Enable specialization of functions that take a literal constant as an "
         "argument"));
 
-bool InstCostVisitor::canEliminateSuccessor(BasicBlock *BB, BasicBlock *Succ,
-                                         DenseSet<BasicBlock *> &DeadBlocks) {
+bool InstCostVisitor::canEliminateSuccessor(BasicBlock *BB,
+                                            BasicBlock *Succ) const {
   unsigned I = 0;
-  return all_of(predecessors(Succ),
-    [&I, BB, Succ, &DeadBlocks] (BasicBlock *Pred) {
+  return all_of(predecessors(Succ), [&I, BB, Succ, this](BasicBlock *Pred) {
     return I++ < MaxBlockPredecessors &&
-      (Pred == BB || Pred == Succ || DeadBlocks.contains(Pred));
+           (Pred == BB || Pred == Succ || !isBlockExecutable(Pred));
   });
 }
 
@@ -116,6 +115,7 @@ Cost InstCostVisitor::estimateBasicBlocks(
     // These blocks are considered dead as far as the InstCostVisitor
     // is concerned. They haven't been proven dead yet by the Solver,
     // but may become if we propagate the specialization arguments.
+    assert(Solver.isBlockExecutable(BB) && "BB already found dead by IPSCCP!");
     if (!DeadBlocks.insert(BB).second)
       continue;
 
@@ -134,16 +134,17 @@ Cost InstCostVisitor::estimateBasicBlocks(
     // Keep adding dead successors to the list as long as they are
     // executable and only reachable from dead blocks.
     for (BasicBlock *SuccBB : successors(BB))
-      if (isBlockExecutable(SuccBB) &&
-          canEliminateSuccessor(BB, SuccBB, DeadBlocks))
+      if (isBlockExecutable(SuccBB) && canEliminateSuccessor(BB, SuccBB))
         WorkList.push_back(SuccBB);
   }
   return CodeSize;
 }
 
-static Constant *findConstantFor(Value *V, ConstMap &KnownConstants) {
+Constant *InstCostVisitor::findConstantFor(Value *V) const {
   if (auto *C = dyn_cast<Constant>(V))
     return C;
+  if (auto *C = Solver.getConstantOrNull(V))
+    return C;
   return KnownConstants.lookup(V);
 }
 
@@ -266,7 +267,7 @@ Cost InstCostVisitor::estimateSwitchInst(SwitchInst &I) {
   for (const auto &Case : I.cases()) {
     BasicBlock *BB = Case.getCaseSuccessor();
     if (BB != Succ && isBlockExecutable(BB) &&
-        canEliminateSuccessor(I.getParent(), BB, DeadBlocks))
+        canEliminateSuccessor(I.getParent(), BB))
       WorkList.push_back(BB);
   }
 
@@ -283,8 +284,7 @@ Cost InstCostVisitor::estimateBranchInst(BranchInst &I) {
   // Initialize the worklist with the dead successor as long as
   // it is executable and has a unique predecessor.
   SmallVector<BasicBlock *> WorkList;
-  if (isBlockExecutable(Succ) &&
-      canEliminateSuccessor(I.getParent(), Succ, DeadBlocks))
+  if (isBlockExecutable(Succ) && canEliminateSuccessor(I.getParent(), Succ))
     WorkList.push_back(Succ);
 
   return estimateBasicBlocks(WorkList);
@@ -312,10 +312,10 @@ bool InstCostVisitor::discoverTransitivelyIncomingValues(
 
       // Disregard self-references and dead incoming values.
       if (auto *Inst = dyn_cast<Instruction>(V))
-        if (Inst == PN || DeadBlocks.contains(PN->getIncomingBlock(I)))
+        if (Inst == PN || !isBlockExecutable(PN->getIncomingBlock(I)))
           continue;
 
-      if (Constant *C = findConstantFor(V, KnownConstants)) {
+      if (Constant *C = findConstantFor(V)) {
         // Not all incoming values are the same constant. Bail immediately.
         if (C != Const)
           return false;
@@ -347,10 +347,10 @@ Constant *InstCostVisitor::visitPHINode(PHINode &I) {
 
     // Disregard self-references and dead incoming values.
     if (auto *Inst = dyn_cast<Instruction>(V))
-      if (Inst == &I || DeadBlocks.contains(I.getIncomingBlock(Idx)))
+      if (Inst == &I || !isBlockExecutable(I.getIncomingBlock(Idx)))
         continue;
 
-    if (Constant *C = findConstantFor(V, KnownConstants)) {
+    if (Constant *C = findConstantFor(V)) {
       if (!Const)
         Const = C;
       // Not all incoming values are the same constant. Bail immediately.
@@ -415,7 +415,7 @@ Constant *InstCostVisitor::visitCallBase(CallBase &I) {
 
   for (unsigned Idx = 0, E = I.getNumOperands() - 1; Idx != E; ++Idx) {
     Value *V = I.getOperand(Idx);
-    Constant *C = findConstantFor(V, KnownConstants);
+    Constant *C = findConstantFor(V);
     if (!C)
       return nullptr;
     Operands.push_back(C);
@@ -439,7 +439,7 @@ Constant *InstCostVisitor::visitGetElementPtrInst(GetElementPtrInst &I) {
 
   for (unsigned Idx = 0, E = I.getNumOperands(); Idx != E; ++Idx) {
     Value *V = I.getOperand(Idx);
-    Constant *C = findConstantFor(V, KnownConstants);
+    Constant *C = findConstantFor(V);
     if (!C)
       return nullptr;
     Operands.push_back(C);
@@ -455,9 +455,9 @@ Constant *InstCostVisitor::visitSelectInst(SelectInst &I) {
   if (I.getCondition() == LastVisited->first) {
     Value *V = LastVisited->second->isZeroValue() ? I.getFalseValue()
                                                   : I.getTrueValue();
-    return findConstantFor(V, KnownConstants);
+    return findConstantFor(V);
   }
-  if (Constant *Condition = findConstantFor(I.getCondition(), KnownConstants))
+  if (Constant *Condition = findConstantFor(I.getCondition()))
     if ((I.getTrueValue() == LastVisited->first && Condition->isOneValue()) ||
         (I.getFalseValue() == LastVisited->first && Condition->isZeroValue()))
       return LastVisited->second;
@@ -475,7 +475,7 @@ Constant *InstCostVisitor::visitCmpInst(CmpInst &I) {
   Constant *Const = LastVisited->second;
   bool ConstOnRHS = I.getOperand(1) == LastVisited->first;
   Value *V = ConstOnRHS ? I.getOperand(0) : I.getOperand(1);
-  Constant *Other = findConstantFor(V, KnownConstants);
+  Constant *Other = findConstantFor(V);
 
   if (Other) {
     if (ConstOnRHS)
@@ -503,7 +503,7 @@ Constant *InstCostVisitor::visitBinaryOperator(BinaryOperator &I) {
 
   bool ConstOnRHS = I.getOperand(1) == LastVisited->first;
   Value *V = ConstOnRHS ? I.getOperand(0) : I.getOperand(1);
-  Constant *Other = findConstantFor(V, KnownConstants);
+  Constant *Other = findConstantFor(V);
   Value *OtherVal = Other ? Other : V;
   Value *ConstVal = LastVisited->second;
 

llvm/test/Transforms/FunctionSpecialization/solver-constants.ll

@@ -0,0 +1,66 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --include-generated-funcs --version 5
+; RUN: opt -passes="ipsccp<func-spec>" -funcspec-min-function-size=1       \
+; RUN:                                 -funcspec-for-literal-constant=true \
+; RUN:                                 -funcspec-min-codesize-savings=50   \
+; RUN:                                 -funcspec-min-latency-savings=0     \
+; RUN:                                 -S < %s | FileCheck %s
+
+; Verify that we are able to estimate the codesize savings arising from a branch
+; based on a binary operator, where one operand is already found constant by
+; IPSCCP.
+define i32 @main(i1 %flag) {
+  %notspec = call i32 @test(i1 %flag, i1 false)
+  %spec = call i32 @test(i1 false, i1 false)
+  %sum = add i32 %notspec, %spec
+  ret i32 %sum
+}
+
+define internal i32 @test(i1 %argflag, i1 %constflag) {
+entry:
+  %cond = or i1 %argflag, %constflag
+  br i1 %cond, label %if.then, label %if.end
+
+if.then:
+  call void @do_something()
+  call void @do_something()
+  call void @do_something()
+  call void @do_something()
+  br label %if.end
+
+if.end:
+  %res = phi i32 [ 0, %entry ], [ 1, %if.then]
+  ret i32 %res
+}
+
+declare void @do_something()
+; CHECK-LABEL: define range(i32 0, 2) i32 @main(
+; CHECK-SAME: i1 [[FLAG:%.*]]) {
+; CHECK-NEXT:    [[NOTSPEC:%.*]] = call i32 @test(i1 [[FLAG]], i1 false)
+; CHECK-NEXT:    [[SPEC:%.*]] = call i32 @test.specialized.1(i1 false, i1 false)
+; CHECK-NEXT:    [[SUM:%.*]] = add nuw nsw i32 [[NOTSPEC]], 0
+; CHECK-NEXT:    ret i32 [[SUM]]
+;
+;
+; CHECK-LABEL: define internal range(i32 0, 2) i32 @test(
+; CHECK-SAME: i1 [[ARGFLAG:%.*]], i1 [[CONSTFLAG:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    [[COND:%.*]] = or i1 [[ARGFLAG]], false
+; CHECK-NEXT:    br i1 [[COND]], label %[[IF_THEN:.*]], label %[[IF_END:.*]]
+; CHECK:       [[IF_THEN]]:
+; CHECK-NEXT:    call void @do_something()
+; CHECK-NEXT:    call void @do_something()
+; CHECK-NEXT:    call void @do_something()
+; CHECK-NEXT:    call void @do_something()
+; CHECK-NEXT:    br label %[[IF_END]]
+; CHECK:       [[IF_END]]:
+; CHECK-NEXT:    [[RES:%.*]] = phi i32 [ 0, %[[ENTRY]] ], [ 1, %[[IF_THEN]] ]
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+;
+; CHECK-LABEL: define internal i32 @test.specialized.1(
+; CHECK-SAME: i1 [[ARGFLAG:%.*]], i1 [[CONSTFLAG:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    br label %[[IF_END:.*]]
+; CHECK:       [[IF_END]]:
+; CHECK-NEXT:    ret i32 poison
+;

llvm/test/Transforms/FunctionSpecialization/solver-dead-blocks.ll

@@ -0,0 +1,74 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --include-generated-funcs --version 5
+; RUN: opt -passes="ipsccp<func-spec>" -funcspec-min-function-size=1       \
+; RUN:                                 -funcspec-for-literal-constant=true \
+; RUN:                                 -funcspec-min-codesize-savings=50   \
+; RUN:                                 -funcspec-min-latency-savings=0     \
+; RUN:                                 -S < %s | FileCheck %s
+
+; Verify that we are able to estimate the codesize savings arising from a block
+; which is found dead, where the block has a predecessor that was found dead by
+; IPSCCP.
+define i32 @main(i1 %flag) {
+  %notspec = call i32 @test(i1 %flag, i1 true)
+  %spec = call i32 @test(i1 true, i1 true)
+  %sum = add i32 %notspec, %spec
+  ret i32 %sum
+}
+
+define internal i32 @test(i1 %argflag, i1 %constflag) {
+entry:
+  br i1 %argflag, label %block1, label %block3
+
+block1:
+  br i1 %constflag, label %end, label %block2
+
+block2:
+  br label %block3
+
+block3:
+  call void @do_something()
+  call void @do_something()
+  call void @do_something()
+  call void @do_something()
+  br label %end
+
+end:
+  %res = phi i32 [ 0, %block1 ], [ 1, %block3]
+  ret i32 %res
+}
+
+declare void @do_something()
+; CHECK-LABEL: define range(i32 0, 2) i32 @main(
+; CHECK-SAME: i1 [[FLAG:%.*]]) {
+; CHECK-NEXT:    [[NOTSPEC:%.*]] = call i32 @test(i1 [[FLAG]], i1 true)
+; CHECK-NEXT:    [[SPEC:%.*]] = call i32 @test.specialized.1(i1 true, i1 true)
+; CHECK-NEXT:    [[SUM:%.*]] = add nuw nsw i32 [[NOTSPEC]], 0
+; CHECK-NEXT:    ret i32 [[SUM]]
+;
+;
+; CHECK-LABEL: define internal range(i32 0, 2) i32 @test(
+; CHECK-SAME: i1 [[ARGFLAG:%.*]], i1 [[CONSTFLAG:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    br i1 [[ARGFLAG]], label %[[BLOCK1:.*]], label %[[BLOCK3:.*]]
+; CHECK:       [[BLOCK1]]:
+; CHECK-NEXT:    br label %[[END:.*]]
+; CHECK:       [[BLOCK3]]:
+; CHECK-NEXT:    call void @do_something()
+; CHECK-NEXT:    call void @do_something()
+; CHECK-NEXT:    call void @do_something()
+; CHECK-NEXT:    call void @do_something()
+; CHECK-NEXT:    br label %[[END]]
+; CHECK:       [[END]]:
+; CHECK-NEXT:    [[RES:%.*]] = phi i32 [ 0, %[[BLOCK1]] ], [ 1, %[[BLOCK3]] ]
+; CHECK-NEXT:    ret i32 [[RES]]
+;
+;
+; CHECK-LABEL: define internal i32 @test.specialized.1(
+; CHECK-SAME: i1 [[ARGFLAG:%.*]], i1 [[CONSTFLAG:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    br label %[[BLOCK1:.*]]
+; CHECK:       [[BLOCK1]]:
+; CHECK-NEXT:    br label %[[END:.*]]
+; CHECK:       [[END]]:
+; CHECK-NEXT:    ret i32 poison
+;