[PATCH] D157312: [InstCombine] Add transforms for `(or/and (icmp eq/ne X,0),(icmp eq/ne X,Pow2OrZero))`

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n created this revision.
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`(or (icmp eq X, 0), (icmp eq X, Pow2OrZero))`

  --> `(icmp eq (and X, Pow2OrZero), X)`

`(and (icmp ne X, 0), (icmp ne X, Pow2OrZero))`

  --> `(icmp ne (and X, Pow2OrZero), X)`

Proofs: https://alive2.llvm.org/ce/z/nPo2BN


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D157312

Files:
  llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  llvm/test/Transforms/InstCombine/and-or-icmps.ll


Index: llvm/test/Transforms/InstCombine/and-or-icmps.ll
===================================================================
--- llvm/test/Transforms/InstCombine/and-or-icmps.ll
+++ llvm/test/Transforms/InstCombine/and-or-icmps.ll
@@ -3051,9 +3051,8 @@
 ; CHECK-LABEL: @icmp_eq_or_z_or_pow2orz(
 ; CHECK-NEXT:    [[NY:%.*]] = sub i8 0, [[Y:%.*]]
 ; CHECK-NEXT:    [[POW2ORZ:%.*]] = and i8 [[NY]], [[Y]]
-; CHECK-NEXT:    [[C0:%.*]] = icmp eq i8 [[X:%.*]], 0
-; CHECK-NEXT:    [[CP2:%.*]] = icmp eq i8 [[POW2ORZ]], [[X]]
-; CHECK-NEXT:    [[R:%.*]] = or i1 [[C0]], [[CP2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and i8 [[POW2ORZ]], [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp eq i8 [[TMP1]], [[X]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %ny = sub i8 0, %y
@@ -3069,9 +3068,8 @@
 ; CHECK-LABEL: @icmp_ne_and_z_and_pow2orz(
 ; CHECK-NEXT:    [[NY:%.*]] = sub <2 x i8> zeroinitializer, [[Y:%.*]]
 ; CHECK-NEXT:    [[POW2ORZ:%.*]] = and <2 x i8> [[NY]], [[Y]]
-; CHECK-NEXT:    [[C0:%.*]] = icmp ne <2 x i8> [[X:%.*]], zeroinitializer
-; CHECK-NEXT:    [[CP2:%.*]] = icmp ne <2 x i8> [[POW2ORZ]], [[X]]
-; CHECK-NEXT:    [[R:%.*]] = and <2 x i1> [[C0]], [[CP2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i8> [[POW2ORZ]], [[X:%.*]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ne <2 x i8> [[TMP1]], [[X]]
 ; CHECK-NEXT:    ret <2 x i1> [[R]]
 ;
   %ny = sub <2 x i8> zeroinitializer, %y
Index: llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -739,6 +739,38 @@
   return Builder.CreateICmp(NewPred, Input, RangeEnd);
 }
 
+// (or (icmp eq X, 0), (icmp eq X, Pow2OrZero))
+//      -> (icmp eq (and X, Pow2), X)
+// (and (icmp ne X, 0), (icmp ne X, Pow2OrZero))
+//      -> (icmp ne (and X, Pow2OrZero), X)
+static Value *
+foldAndOrOfICmpsWithPow2AndWithZero(InstCombiner::BuilderTy &Builder,
+                                    ICmpInst *LHS, ICmpInst *RHS, bool IsAnd,
+                                    const SimplifyQuery &Q) {
+  CmpInst::Predicate Pred = IsAnd ? CmpInst::ICMP_NE : CmpInst::ICMP_EQ;
+  // Make sure we have right compares for out op.
+  if (LHS->getPredicate() != Pred || RHS->getPredicate() != Pred)
+    return nullptr;
+
+  // Make it so we can match LHS against the (icmp eq/ne X, 0) just for
+  // simplicity.
+  if (match(RHS->getOperand(1), m_Zero()))
+    std::swap(LHS, RHS);
+
+  Value *Pow2, *Op;
+  // Match the desired pattern:
+  // LHS: (icmp eq/ne X, 0)
+  // RHS: (icmp eq/ne X, Pow2OrZero)
+  if (!match(LHS, m_ICmp(Pred, m_Value(Op), m_Zero())) ||
+      !match(RHS, m_c_ICmp(Pred, m_Specific(Op), m_Value(Pow2))) ||
+      !isKnownToBeAPowerOfTwo(Pow2, Q.DL, /*OrZero*/ true, /*Depth*/ 0, Q.AC,
+                              Q.CxtI, Q.DT))
+    return nullptr;
+
+  Value *And = Builder.CreateAnd(Op, Pow2);
+  return Builder.CreateICmp(Pred, And, Op);
+}
+
 // Fold (iszero(A & K1) | iszero(A & K2)) -> (A & (K1 | K2)) != (K1 | K2)
 // Fold (!iszero(A & K1) & !iszero(A & K2)) -> (A & (K1 | K2)) == (K1 | K2)
 Value *InstCombinerImpl::foldAndOrOfICmpsOfAndWithPow2(ICmpInst *LHS,
@@ -3048,6 +3080,11 @@
   if (Value *V = foldAndOrOfICmpsOfAndWithPow2(LHS, RHS, &I, IsAnd, IsLogical))
     return V;
 
+  if (!IsLogical)
+    if (Value *V =
+            foldAndOrOfICmpsWithPow2AndWithZero(Builder, LHS, RHS, IsAnd, Q))
+      return V;
+
   ICmpInst::Predicate PredL = LHS->getPredicate(), PredR = RHS->getPredicate();
   Value *LHS0 = LHS->getOperand(0), *RHS0 = RHS->getOperand(0);
   Value *LHS1 = LHS->getOperand(1), *RHS1 = RHS->getOperand(1);


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