Merge commit '0daa13645702' from apple/stable/20200714 into swift/main

Author: git apple-llvm automerger

llvm/include/llvm/Analysis/ConstraintSystem.h

@@ -11,6 +11,7 @@
 
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 
 #include <string>
@@ -39,22 +40,28 @@ class ConstraintSystem {
   bool mayHaveSolutionImpl();
 
 public:
-  void addVariableRow(const SmallVector<int64_t, 8> &R) {
+  bool addVariableRow(const SmallVector<int64_t, 8> &R) {
     assert(Constraints.empty() || R.size() == Constraints.back().size());
+    // If all variable coefficients are 0, the constraint does not provide any
+    // usable information.
+    if (all_of(makeArrayRef(R).drop_front(1), [](int64_t C) { return C == 0; }))
+      return false;
+
     for (const auto &C : R) {
       auto A = std::abs(C);
       GCD = APIntOps::GreatestCommonDivisor({32, (uint32_t)A}, {32, GCD})
                 .getZExtValue();
     }
     Constraints.push_back(R);
+    return true;
   }
 
-  void addVariableRowFill(const SmallVector<int64_t, 8> &R) {
+  bool addVariableRowFill(const SmallVector<int64_t, 8> &R) {
     for (auto &CR : Constraints) {
       while (CR.size() != R.size())
         CR.push_back(0);
     }
-    addVariableRow(R);
+    return addVariableRow(R);
   }
 
   /// Returns true if there may be a solution for the constraints in the system.
@@ -72,6 +79,9 @@ class ConstraintSystem {
   bool isConditionImplied(SmallVector<int64_t, 8> R);
 
   void popLastConstraint() { Constraints.pop_back(); }
+
+  /// Returns the number of rows in the constraint system.
+  unsigned size() const { return Constraints.size(); }
 };
 } // namespace llvm
 

llvm/lib/Analysis/ConstraintSystem.cpp

@@ -84,6 +84,9 @@ bool ConstraintSystem::eliminateUsingFM() {
                      .getZExtValue();
       }
       NewSystem.push_back(std::move(NR));
+      // Give up if the new system gets too big.
+      if (NewSystem.size() > 500)
+        return false;
     }
   }
   Constraints = std::move(NewSystem);
@@ -133,13 +136,18 @@ void ConstraintSystem::dump() const {
 }
 
 bool ConstraintSystem::mayHaveSolution() {
-  dump();
+  LLVM_DEBUG(dump());
   bool HasSolution = mayHaveSolutionImpl();
   LLVM_DEBUG(dbgs() << (HasSolution ? "sat" : "unsat") << "\n");
   return HasSolution;
 }
 
 bool ConstraintSystem::isConditionImplied(SmallVector<int64_t, 8> R) {
+  // If all variable coefficients are 0, we have 'C >= 0'. If the constant is >=
+  // 0, R is always true, regardless of the system.
+  if (all_of(makeArrayRef(R).drop_front(1), [](int64_t C) { return C == 0; }))
+    return R[0] >= 0;
+
   // If there is no solution with the negation of R added to the system, the
   // condition must hold based on the existing constraints.
   R = ConstraintSystem::negate(R);

llvm/lib/Transforms/IPO/PassManagerBuilder.cpp

@@ -453,6 +453,9 @@ void PassManagerBuilder::addFunctionSimplificationPasses(
   MPM.add(createMemCpyOptPass());             // Remove memcpy / form memset
   MPM.add(createSCCPPass());                  // Constant prop with SCCP
 
+  if (EnableConstraintElimination)
+    MPM.add(createConstraintEliminationPass());
+
   // Delete dead bit computations (instcombine runs after to fold away the dead
   // computations, and then ADCE will run later to exploit any new DCE
   // opportunities that creates).
@@ -1028,6 +1031,9 @@ void PassManagerBuilder::addLTOOptimizationPasses(legacy::PassManagerBase &PM) {
   if (EnableLoopInterchange)
     PM.add(createLoopInterchangePass());
 
+  if (EnableConstraintElimination)
+    PM.add(createConstraintEliminationPass());
+
   // Unroll small loops
   PM.add(createSimpleLoopUnrollPass(OptLevel, DisableUnrollLoops,
                                     ForgetAllSCEVInLoopUnroll));

llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

@@ -63,12 +63,12 @@ static SmallVector<std::pair<int64_t, Value *>, 4> decompose(Value *V) {
               m_NUWShl(m_Value(Op0), m_ConstantInt(CI))))
       return {{0, nullptr},
               {1, GEP->getPointerOperand()},
-              {pow(2, CI->getSExtValue()), Op0}};
+              {std::pow(int64_t(2), CI->getSExtValue()), Op0}};
     if (match(GEP->getOperand(GEP->getNumOperands() - 1),
               m_ZExt(m_NUWShl(m_Value(Op0), m_ConstantInt(CI)))))
       return {{0, nullptr},
               {1, GEP->getPointerOperand()},
-              {pow(2, CI->getSExtValue()), Op0}};
+              {std::pow(int64_t(2), CI->getSExtValue()), Op0}};
 
     return {{0, nullptr},
             {1, GEP->getPointerOperand()},
@@ -346,8 +346,10 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT) {
     if (CB.Not)
       R = ConstraintSystem::negate(R);
 
-    CS.addVariableRowFill(R);
-    DFSInStack.emplace_back(CB.NumIn, CB.NumOut, CB.Condition, CB.Not);
+    // If R has been added to the system, queue it for removal once it goes
+    // out-of-scope.
+    if (CS.addVariableRowFill(R))
+      DFSInStack.emplace_back(CB.NumIn, CB.NumOut, CB.Condition, CB.Not);
   }
 
   return Changed;

llvm/test/Transforms/ConstraintElimination/empty-constraint.ll

@@ -0,0 +1,47 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -constraint-elimination -S %s | FileCheck %s
+
+; Make sure constraints where all variable coefficients are 0 are handled
+; properly.
+
+define i1 @test_1_always_false(i32 %A, i32 %B) {
+; CHECK-LABEL: @test_1_always_false(
+; CHECK-NEXT:    [[C_1:%.*]] = icmp ugt i32 [[A:%.*]], [[A]]
+; CHECK-NEXT:    br i1 [[C_1]], label [[IF_END_I16:%.*]], label [[IF_THEN_I10:%.*]]
+; CHECK:       if.then.i10:
+; CHECK-NEXT:    ret i1 false
+; CHECK:       if.end.i16:
+; CHECK-NEXT:    [[C_2:%.*]] = icmp ugt i32 [[A]], [[A]]
+; CHECK-NEXT:    ret i1 false
+;
+  %c.1 = icmp ugt i32 %A, %A
+  br i1 %c.1, label %if.end.i16, label %if.then.i10
+
+if.then.i10:
+  ret i1 false
+
+if.end.i16:
+  %c.2 = icmp ugt i32 %A, %A
+  ret i1 %c.2
+}
+
+define i1 @test_2_always_true(i32 %A, i32 %B) {
+; CHECK-LABEL: @test_2_always_true(
+; CHECK-NEXT:    [[C_1:%.*]] = icmp uge i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    br i1 [[C_1]], label [[IF_END_I16:%.*]], label [[IF_THEN_I10:%.*]]
+; CHECK:       if.then.i10:
+; CHECK-NEXT:    ret i1 false
+; CHECK:       if.end.i16:
+; CHECK-NEXT:    [[C_2:%.*]] = icmp uge i32 [[A]], [[A]]
+; CHECK-NEXT:    ret i1 true
+;
+  %c.1 = icmp uge i32 %A, %B
+  br i1 %c.1, label %if.end.i16, label %if.then.i10
+
+if.then.i10:
+  ret i1 false
+
+if.end.i16:
+  %c.2 = icmp uge i32 %A, %A
+  ret i1 %c.2
+}

llvm/test/Transforms/ConstraintElimination/large-system-growth.ll

@@ -0,0 +1,86 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -constraint-elimination -S %s | FileCheck %s
+
+; The system for the function below grows quite large. Check to make sure
+; we can handle that scenario.
+define void @test(i64 %x, i8* %y, i8* %z, i8* %w) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT:    [[TMP22:%.*]] = getelementptr inbounds i8, i8* [[Y:%.*]], i64 [[X:%.*]]
+; CHECK-NEXT:    [[TMP26:%.*]] = icmp ult i8* [[TMP22]], [[Z:%.*]]
+; CHECK-NEXT:    br i1 [[TMP26]], label [[BB28:%.*]], label [[EARLY_EXIT:%.*]]
+; CHECK:       early.exit:
+; CHECK-NEXT:    unreachable
+; CHECK:       bb28:
+; CHECK-NEXT:    [[TMP29:%.*]] = getelementptr inbounds i8, i8* [[Y]], i64 [[X]]
+; CHECK-NEXT:    [[TMP30:%.*]] = icmp ult i8* [[TMP29]], [[Z]]
+; CHECK-NEXT:    br i1 true, label [[EARLY_EXIT]], label [[BB32:%.*]]
+; CHECK:       bb32:
+; CHECK-NEXT:    [[TMP33:%.*]] = icmp ult i8* [[TMP29]], [[Z]]
+; CHECK-NEXT:    br i1 true, label [[BB35:%.*]], label [[EARLY_EXIT]]
+; CHECK:       bb35:
+; CHECK-NEXT:    [[TMP36:%.*]] = icmp ult i8* [[Y]], [[Z]]
+; CHECK-NEXT:    br i1 true, label [[EARLY_EXIT]], label [[BB38:%.*]]
+; CHECK:       bb38:
+; CHECK-NEXT:    [[TMP41:%.*]] = icmp ult i8* [[Y]], [[Z]]
+; CHECK-NEXT:    br i1 true, label [[EARLY_EXIT]], label [[BB43:%.*]]
+; CHECK:       bb43:
+; CHECK-NEXT:    [[TMP47:%.*]] = getelementptr inbounds i8, i8* [[W:%.*]], i64 [[X]]
+; CHECK-NEXT:    [[TMP48:%.*]] = icmp ult i8* [[TMP47]], [[Y]]
+; CHECK-NEXT:    br i1 [[TMP48]], label [[EARLY_EXIT]], label [[BB50:%.*]]
+; CHECK:       bb50:
+; CHECK-NEXT:    [[TMP52:%.*]] = getelementptr inbounds i8, i8* [[W]], i64 [[X]]
+; CHECK-NEXT:    [[TMP53:%.*]] = icmp ult i8* [[TMP52]], [[Y]]
+; CHECK-NEXT:    br i1 true, label [[EARLY_EXIT]], label [[BB55:%.*]]
+; CHECK:       bb55:
+; CHECK-NEXT:    [[TMP57:%.*]] = icmp ult i8* [[W]], [[Y]]
+; CHECK-NEXT:    br i1 true, label [[BB59:%.*]], label [[EARLY_EXIT]]
+; CHECK:       bb59:
+; CHECK-NEXT:    [[TMP60:%.*]] = icmp ult i8* [[W]], [[Y]]
+; CHECK-NEXT:    call void @use(i1 true)
+; CHECK-NEXT:    ret void
+;
+  %tmp22 = getelementptr inbounds i8, i8* %y, i64 %x
+  %tmp26 = icmp ult i8* %tmp22, %z
+  br i1 %tmp26, label %bb28, label %early.exit
+
+early.exit:
+  unreachable
+
+bb28:
+  %tmp29 = getelementptr inbounds i8, i8* %y, i64 %x
+  %tmp30 = icmp ult i8* %tmp29, %z
+  br i1 %tmp30, label %early.exit, label %bb32
+
+bb32:
+  %tmp33 = icmp ult i8* %tmp29, %z
+  br i1 %tmp33, label %bb35, label %early.exit
+
+bb35:
+  %tmp36 = icmp ult i8* %y, %z
+  br i1 %tmp36, label %early.exit, label %bb38
+
+bb38:
+  %tmp41 = icmp ult i8* %y, %z
+  br i1 %tmp41, label %early.exit, label %bb43
+
+bb43:
+  %tmp47 = getelementptr inbounds i8, i8* %w, i64 %x
+  %tmp48 = icmp ult i8* %tmp47, %y
+  br i1 %tmp48, label %early.exit, label %bb50
+
+bb50:
+  %tmp52 = getelementptr inbounds i8, i8* %w, i64 %x
+  %tmp53 = icmp ult i8* %tmp52, %y
+  br i1 %tmp53, label %early.exit, label %bb55
+
+bb55:
+  %tmp57 = icmp ult i8* %w, %y
+  br i1 %tmp57, label %bb59, label %early.exit
+
+bb59:
+  %tmp60 = icmp ult i8* %w, %y
+  call void @use(i1 %tmp60)
+  ret void
+}
+
+declare void @use(i1)