[PatternMatch] Stabilize the matching order of commutative matchers

Summary:
Currently, we
1. match `LHS` matcher to the `first` operand of binary operator,
2. and then match `RHS` matcher to the `second` operand of binary operator.
If that does not match, we swap the `LHS` and `RHS` matchers:
1. match `RHS` matcher to the `first` operand of binary operator,
2. and then match `LHS` matcher to the `second` operand of binary operator.

This works ok.
But it complicates writing of commutative matchers, where one would like to match
(`m_Value()`) the value on one side, and use (`m_Specific()`) it on the other side.

This is additionally complicated by the fact that `m_Specific()` stores the `Value *`,
not `Value **`, so it won't work at all out of the box.

The last problem is trivially solved by adding a new `m_c_Specific()` that stores the
`Value **`, not `Value *`. I'm choosing to add a new matcher, not change the existing
one because i guess all the current users are ok with existing behavior,
and this additional pointer indirection may have performance drawbacks.
Also, i'm storing pointer, not reference, because for some mysterious-to-me reason
it did not work with the reference.

The first one appears trivial, too.
Currently, we
1. match `LHS` matcher to the `first` operand of binary operator,
2. and then match `RHS` matcher to the `second` operand of binary operator.
If that does not match, we swap the ~~`LHS` and `RHS` matchers~~ **operands**:
1. match ~~`RHS`~~ **`LHS`** matcher to the ~~`first`~~ **`second`** operand of binary operator,
2. and then match ~~`LHS`~~ **`RHS`** matcher to the ~~`second`~ **`first`** operand of binary operator.

Surprisingly, `$ ninja check-llvm` still passes with this.
But i expect the bots will disagree..

The motivational unittest is included.
I'd like to use this in D45664.

Reviewers: spatel, craig.topper, arsenm, RKSimon

Reviewed By: craig.topper

Subscribers: xbolva00, wdng, llvm-commits

Differential Revision: https://reviews.llvm.org/D45828

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@331085 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/IR/PatternMatch.h

@@ -489,6 +489,22 @@ struct specificval_ty {
 /// Match if we have a specific specified value.
 inline specificval_ty m_Specific(const Value *V) { return V; }
 
+/// Stores a reference to the Value *, not the Value * itself,
+/// thus can be used in commutative matchers.
+template <typename Class> struct deferredval_ty {
+  Class *const &Val;
+
+  deferredval_ty(Class *const &V) : Val(V) {}
+
+  template <typename ITy> bool match(ITy *const V) { return V == Val; }
+};
+
+/// A commutative-friendly version of m_Specific().
+inline deferredval_ty<Value> m_Deferred(Value *const &V) { return V; }
+inline deferredval_ty<const Value> m_Deferred(const Value *const &V) {
+  return V;
+}
+
 /// Match a specified floating point value or vector of all elements of
 /// that value.
 struct specific_fpval {
@@ -562,13 +578,15 @@ struct AnyBinaryOp_match {
   LHS_t L;
   RHS_t R;
 
+  // The evaluation order is always stable, regardless of Commutability.
+  // The LHS is always matched first.
   AnyBinaryOp_match(const LHS_t &LHS, const RHS_t &RHS) : L(LHS), R(RHS) {}
 
   template <typename OpTy> bool match(OpTy *V) {
     if (auto *I = dyn_cast<BinaryOperator>(V))
       return (L.match(I->getOperand(0)) && R.match(I->getOperand(1))) ||
-             (Commutable && R.match(I->getOperand(0)) &&
-              L.match(I->getOperand(1)));
+             (Commutable && L.match(I->getOperand(1)) &&
+              R.match(I->getOperand(0)));
     return false;
   }
 };
@@ -588,20 +606,22 @@ struct BinaryOp_match {
   LHS_t L;
   RHS_t R;
 
+  // The evaluation order is always stable, regardless of Commutability.
+  // The LHS is always matched first.
   BinaryOp_match(const LHS_t &LHS, const RHS_t &RHS) : L(LHS), R(RHS) {}
 
   template <typename OpTy> bool match(OpTy *V) {
     if (V->getValueID() == Value::InstructionVal + Opcode) {
       auto *I = cast<BinaryOperator>(V);
       return (L.match(I->getOperand(0)) && R.match(I->getOperand(1))) ||
-             (Commutable && R.match(I->getOperand(0)) &&
-              L.match(I->getOperand(1)));
+             (Commutable && L.match(I->getOperand(1)) &&
+              R.match(I->getOperand(0)));
     }
     if (auto *CE = dyn_cast<ConstantExpr>(V))
       return CE->getOpcode() == Opcode &&
              ((L.match(CE->getOperand(0)) && R.match(CE->getOperand(1))) ||
-              (Commutable && R.match(CE->getOperand(0)) &&
-               L.match(CE->getOperand(1))));
+              (Commutable && L.match(CE->getOperand(1)) &&
+               R.match(CE->getOperand(0))));
     return false;
   }
 };
@@ -926,14 +946,16 @@ struct CmpClass_match {
   LHS_t L;
   RHS_t R;
 
+  // The evaluation order is always stable, regardless of Commutability.
+  // The LHS is always matched first.
   CmpClass_match(PredicateTy &Pred, const LHS_t &LHS, const RHS_t &RHS)
       : Predicate(Pred), L(LHS), R(RHS) {}
 
   template <typename OpTy> bool match(OpTy *V) {
     if (auto *I = dyn_cast<Class>(V))
       if ((L.match(I->getOperand(0)) && R.match(I->getOperand(1))) ||
-          (Commutable && R.match(I->getOperand(0)) &&
-           L.match(I->getOperand(1)))) {
+          (Commutable && L.match(I->getOperand(1)) &&
+           R.match(I->getOperand(0)))) {
         Predicate = I->getPredicate();
         return true;
       }
@@ -1251,6 +1273,8 @@ struct MaxMin_match {
   LHS_t L;
   RHS_t R;
 
+  // The evaluation order is always stable, regardless of Commutability.
+  // The LHS is always matched first.
   MaxMin_match(const LHS_t &LHS, const RHS_t &RHS) : L(LHS), R(RHS) {}
 
   template <typename OpTy> bool match(OpTy *V) {
@@ -1277,7 +1301,7 @@ struct MaxMin_match {
       return false;
     // It does!  Bind the operands.
     return (L.match(LHS) && R.match(RHS)) ||
-           (Commutable && R.match(LHS) && L.match(RHS));
+           (Commutable && L.match(RHS) && R.match(LHS));
   }
 };
 

lib/Analysis/ValueTracking.cpp

@@ -982,12 +982,9 @@ static void computeKnownBitsFromOperator(const Operator *I, KnownBits &Known,
     // matching the form add(x, add(x, y)) where y is odd.
     // TODO: This could be generalized to clearing any bit set in y where the
     // following bit is known to be unset in y.
-    Value *Y = nullptr;
+    Value *X = nullptr, *Y = nullptr;
     if (!Known.Zero[0] && !Known.One[0] &&
-        (match(I->getOperand(0), m_Add(m_Specific(I->getOperand(1)),
-                                       m_Value(Y))) ||
-         match(I->getOperand(1), m_Add(m_Specific(I->getOperand(0)),
-                                       m_Value(Y))))) {
+        match(I, m_c_BinOp(m_Value(X), m_Add(m_Deferred(X), m_Value(Y))))) {
       Known2.resetAll();
       computeKnownBits(Y, Known2, Depth + 1, Q);
       if (Known2.countMinTrailingOnes() > 0)

lib/Transforms/InstCombine/InstCombineAddSub.cpp

@@ -1363,26 +1363,15 @@ Instruction *InstCombiner::visitAdd(BinaryOperator &I) {
   }
 
   // (add (xor A, B) (and A, B)) --> (or A, B)
-  if (match(LHS, m_Xor(m_Value(A), m_Value(B))) &&
-      match(RHS, m_c_And(m_Specific(A), m_Specific(B))))
-    return BinaryOperator::CreateOr(A, B);
-
   // (add (and A, B) (xor A, B)) --> (or A, B)
-  if (match(RHS, m_Xor(m_Value(A), m_Value(B))) &&
-      match(LHS, m_c_And(m_Specific(A), m_Specific(B))))
+  if (match(&I, m_c_BinOp(m_Xor(m_Value(A), m_Value(B)),
+                          m_c_And(m_Deferred(A), m_Deferred(B)))))
     return BinaryOperator::CreateOr(A, B);
 
   // (add (or A, B) (and A, B)) --> (add A, B)
-  if (match(LHS, m_Or(m_Value(A), m_Value(B))) &&
-      match(RHS, m_c_And(m_Specific(A), m_Specific(B)))) {
-    I.setOperand(0, A);
-    I.setOperand(1, B);
-    return &I;
-  }
-
   // (add (and A, B) (or A, B)) --> (add A, B)
-  if (match(RHS, m_Or(m_Value(A), m_Value(B))) &&
-      match(LHS, m_c_And(m_Specific(A), m_Specific(B)))) {
+  if (match(&I, m_c_BinOp(m_Or(m_Value(A), m_Value(B)),
+                          m_c_And(m_Deferred(A), m_Deferred(B))))) {
     I.setOperand(0, A);
     I.setOperand(1, B);
     return &I;

lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -1288,17 +1288,17 @@ static Instruction *foldAndToXor(BinaryOperator &I,
   // Operand complexity canonicalization guarantees that the 'or' is Op0.
   // (A | B) & ~(A & B) --> A ^ B
   // (A | B) & ~(B & A) --> A ^ B
-  if (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
-      match(Op1, m_Not(m_c_And(m_Specific(A), m_Specific(B)))))
+  if (match(&I, m_BinOp(m_Or(m_Value(A), m_Value(B)),
+                        m_Not(m_c_And(m_Deferred(A), m_Deferred(B))))))
     return BinaryOperator::CreateXor(A, B);
 
   // (A | ~B) & (~A | B) --> ~(A ^ B)
   // (A | ~B) & (B | ~A) --> ~(A ^ B)
   // (~B | A) & (~A | B) --> ~(A ^ B)
   // (~B | A) & (B | ~A) --> ~(A ^ B)
   if (Op0->hasOneUse() || Op1->hasOneUse())
-    if (match(Op0, m_c_Or(m_Value(A), m_Not(m_Value(B)))) &&
-        match(Op1, m_c_Or(m_Not(m_Specific(A)), m_Specific(B))))
+    if (match(&I, m_BinOp(m_c_Or(m_Value(A), m_Not(m_Value(B))),
+                          m_c_Or(m_Not(m_Deferred(A)), m_Deferred(B)))))
       return BinaryOperator::CreateNot(Builder.CreateXor(A, B));
 
   return nullptr;
@@ -2294,10 +2294,8 @@ static Instruction *foldXorToXor(BinaryOperator &I,
   // (A & B) ^ (B | A) -> A ^ B
   // (A | B) ^ (A & B) -> A ^ B
   // (A | B) ^ (B & A) -> A ^ B
-  if ((match(Op0, m_And(m_Value(A), m_Value(B))) &&
-       match(Op1, m_c_Or(m_Specific(A), m_Specific(B)))) ||
-      (match(Op0, m_Or(m_Value(A), m_Value(B))) &&
-       match(Op1, m_c_And(m_Specific(A), m_Specific(B))))) {
+  if (match(&I, m_c_Xor(m_And(m_Value(A), m_Value(B)),
+                        m_c_Or(m_Deferred(A), m_Deferred(B))))) {
     I.setOperand(0, A);
     I.setOperand(1, B);
     return &I;
@@ -2307,10 +2305,8 @@ static Instruction *foldXorToXor(BinaryOperator &I,
   // (~B | A) ^ (~A | B) -> A ^ B
   // (~A | B) ^ (A | ~B) -> A ^ B
   // (B | ~A) ^ (A | ~B) -> A ^ B
-  if ((match(Op0, m_Or(m_Value(A), m_Not(m_Value(B)))) &&
-       match(Op1, m_c_Or(m_Not(m_Specific(A)), m_Specific(B)))) ||
-      (match(Op0, m_Or(m_Not(m_Value(A)), m_Value(B))) &&
-       match(Op1, m_c_Or(m_Specific(A), m_Not(m_Specific(B)))))) {
+  if (match(&I, m_Xor(m_c_Or(m_Value(A), m_Not(m_Value(B))),
+                      m_c_Or(m_Not(m_Deferred(A)), m_Deferred(B))))) {
     I.setOperand(0, A);
     I.setOperand(1, B);
     return &I;
@@ -2320,10 +2316,8 @@ static Instruction *foldXorToXor(BinaryOperator &I,
   // (~B & A) ^ (~A & B) -> A ^ B
   // (~A & B) ^ (A & ~B) -> A ^ B
   // (B & ~A) ^ (A & ~B) -> A ^ B
-  if ((match(Op0, m_And(m_Value(A), m_Not(m_Value(B)))) &&
-       match(Op1, m_c_And(m_Not(m_Specific(A)), m_Specific(B)))) ||
-      (match(Op0, m_And(m_Not(m_Value(A)), m_Value(B))) &&
-       match(Op1, m_c_And(m_Specific(A), m_Not(m_Specific(B)))))) {
+  if (match(&I, m_Xor(m_c_And(m_Value(A), m_Not(m_Value(B))),
+                      m_c_And(m_Not(m_Deferred(A)), m_Deferred(B))))) {
     I.setOperand(0, A);
     I.setOperand(1, B);
     return &I;

test/Transforms/InstCombine/and-or-not.ll

@@ -333,7 +333,7 @@ define i32 @xor_to_xor3(i32 %a, i32 %b) {
 
 define i32 @xor_to_xor4(i32 %a, i32 %b) {
 ; CHECK-LABEL: @xor_to_xor4(
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[B:%.*]], [[A:%.*]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %or = or i32 %a, %b
@@ -389,7 +389,7 @@ define i32 @xor_to_xor7(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xor7(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[A]], [[B]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[B]], [[A]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32
@@ -408,7 +408,7 @@ define i32 @xor_to_xor8(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xor8(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[A]], [[B]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[B]], [[A]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32
@@ -465,7 +465,7 @@ define i32 @xor_to_xor11(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xor11(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[A]], [[B]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[B]], [[A]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32
@@ -484,7 +484,7 @@ define i32 @xor_to_xor12(float %fa, float %fb) {
 ; CHECK-LABEL: @xor_to_xor12(
 ; CHECK-NEXT:    [[A:%.*]] = fptosi float [[FA:%.*]] to i32
 ; CHECK-NEXT:    [[B:%.*]] = fptosi float [[FB:%.*]] to i32
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[A]], [[B]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[B]], [[A]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %a = fptosi float %fa to i32

test/Transforms/InstCombine/or-xor.ll

@@ -188,7 +188,7 @@ define i32 @test13(i32 %x, i32 %y) {
 ; ((x | ~y) ^ (~x | y)) -> x ^ y
 define i32 @test14(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test14(
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1
@@ -201,7 +201,7 @@ define i32 @test14(i32 %x, i32 %y) {
 
 define i32 @test14_commuted(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test14_commuted(
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1
@@ -215,7 +215,7 @@ define i32 @test14_commuted(i32 %x, i32 %y) {
 ; ((x & ~y) ^ (~x & y)) -> x ^ y
 define i32 @test15(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test15(
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1
@@ -228,7 +228,7 @@ define i32 @test15(i32 %x, i32 %y) {
 
 define i32 @test15_commuted(i32 %x, i32 %y) {
 ; CHECK-LABEL: @test15_commuted(
-; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[Y:%.*]], [[X:%.*]]
+; CHECK-NEXT:    [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[XOR]]
 ;
   %noty = xor i32 %y, -1

unittests/IR/PatternMatch.cpp

@@ -65,6 +65,56 @@ TEST_F(PatternMatchTest, OneUse) {
   EXPECT_FALSE(m_OneUse(m_Value()).match(Leaf));
 }
 
+TEST_F(PatternMatchTest, CommutativeDeferredValue) {
+  Value *X = IRB.getInt32(1);
+  Value *Y = IRB.getInt32(2);
+
+  {
+    Value *tX = X;
+    EXPECT_TRUE(match(X, m_Deferred(tX)));
+    EXPECT_FALSE(match(Y, m_Deferred(tX)));
+  }
+  {
+    const Value *tX = X;
+    EXPECT_TRUE(match(X, m_Deferred(tX)));
+    EXPECT_FALSE(match(Y, m_Deferred(tX)));
+  }
+  {
+    Value *const tX = X;
+    EXPECT_TRUE(match(X, m_Deferred(tX)));
+    EXPECT_FALSE(match(Y, m_Deferred(tX)));
+  }
+  {
+    const Value *const tX = X;
+    EXPECT_TRUE(match(X, m_Deferred(tX)));
+    EXPECT_FALSE(match(Y, m_Deferred(tX)));
+  }
+
+  {
+    Value *tX = nullptr;
+    EXPECT_TRUE(match(IRB.CreateAnd(X, X), m_And(m_Value(tX), m_Deferred(tX))));
+    EXPECT_EQ(tX, X);
+  }
+  {
+    Value *tX = nullptr;
+    EXPECT_FALSE(
+        match(IRB.CreateAnd(X, Y), m_c_And(m_Value(tX), m_Deferred(tX))));
+  }
+
+  auto checkMatch = [X, Y](Value *Pattern) {
+    Value *tX = nullptr, *tY = nullptr;
+    EXPECT_TRUE(match(
+        Pattern, m_c_And(m_Value(tX), m_c_And(m_Deferred(tX), m_Value(tY)))));
+    EXPECT_EQ(tX, X);
+    EXPECT_EQ(tY, Y);
+  };
+
+  checkMatch(IRB.CreateAnd(X, IRB.CreateAnd(X, Y)));
+  checkMatch(IRB.CreateAnd(X, IRB.CreateAnd(Y, X)));
+  checkMatch(IRB.CreateAnd(IRB.CreateAnd(X, Y), X));
+  checkMatch(IRB.CreateAnd(IRB.CreateAnd(Y, X), X));
+}
+
 TEST_F(PatternMatchTest, FloatingPointOrderedMin) {
   Type *FltTy = IRB.getFloatTy();
   Value *L = ConstantFP::get(FltTy, 1.0);