[PATCH] D144608: [InstCombine] Add transforms for `(icmp {u|s}ge/le (xor X, Y), X)`

[Noah Goldstein via Phabricator via llvm-commits]

goldstein.w.n updated this revision to Diff 514066.
goldstein.w.n added a comment.

Rebase


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D144608/new/

https://reviews.llvm.org/D144608

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll


Index: llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll
===================================================================
--- llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll
+++ llvm/test/Transforms/InstCombine/icmp-of-xor-x.ll
@@ -9,7 +9,7 @@
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
 ; CHECK-NEXT:    [[XOR:%.*]] = xor i8 [[X:%.*]], [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp uge i8 [[XOR]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ugt i8 [[XOR]], [[X]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %ynz = icmp ne i8 %y, 0
@@ -34,7 +34,7 @@
 ; CHECK-LABEL: @xor_ule_2(
 ; CHECK-NEXT:    [[Y:%.*]] = or <2 x i8> [[YY:%.*]], <i8 9, i8 8>
 ; CHECK-NEXT:    [[XOR:%.*]] = xor <2 x i8> [[Y]], [[X:%.*]]
-; CHECK-NEXT:    [[R:%.*]] = icmp ule <2 x i8> [[XOR]], [[X]]
+; CHECK-NEXT:    [[R:%.*]] = icmp ult <2 x i8> [[XOR]], [[X]]
 ; CHECK-NEXT:    ret <2 x i1> [[R]]
 ;
   %y = or <2 x i8> %yy, <i8 9, i8 8>
@@ -49,7 +49,7 @@
 ; CHECK-NEXT:    [[YNZ:%.*]] = icmp ne i8 [[Y:%.*]], 0
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[YNZ]])
 ; CHECK-NEXT:    [[XOR:%.*]] = xor i8 [[X]], [[Y]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sle i8 [[X]], [[XOR]]
+; CHECK-NEXT:    [[R:%.*]] = icmp sgt i8 [[XOR]], [[X]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %x = add i8 %xx, %z
@@ -65,7 +65,7 @@
 ; CHECK-NEXT:    [[X:%.*]] = mul i8 [[XX:%.*]], [[XX]]
 ; CHECK-NEXT:    [[Y:%.*]] = or i8 [[YY:%.*]], -128
 ; CHECK-NEXT:    [[XOR:%.*]] = xor i8 [[Y]], [[X]]
-; CHECK-NEXT:    [[R:%.*]] = icmp sge i8 [[X]], [[XOR]]
+; CHECK-NEXT:    [[R:%.*]] = icmp slt i8 [[XOR]], [[X]]
 ; CHECK-NEXT:    ret i1 [[R]]
 ;
   %x = mul i8 %xx, %xx
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -4153,6 +4153,30 @@
   return nullptr;
 }
 
+static Instruction *foldICmpXorXX(ICmpInst &I, const SimplifyQuery &Q,
+                                  InstCombinerImpl &IC) {
+  Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1), *A;
+  // Normalize xor operand as operand 0.
+  CmpInst::Predicate Pred = I.getPredicate();
+  if (match(Op1, m_c_Xor(m_Specific(Op0), m_Value()))) {
+    std::swap(Op0, Op1);
+    Pred = ICmpInst::getSwappedPredicate(Pred);
+  }
+  if (!match(Op0, m_c_Xor(m_Specific(Op1), m_Value(A))))
+    return nullptr;
+
+  // icmp (X ^ Y_NonZero) u>= X --> icmp (X ^ Y_NonZero) u> X
+  // icmp (X ^ Y_NonZero) u<= X --> icmp (X ^ Y_NonZero) u< X
+  // icmp (X ^ Y_NonZero) s>= X --> icmp (X ^ Y_NonZero) s> X
+  // icmp (X ^ Y_NonZero) s<= X --> icmp (X ^ Y_NonZero) s< X
+  CmpInst::Predicate PredOut = CmpInst::getStrictPredicate(Pred);
+  if (PredOut != Pred &&
+      isKnownNonZero(A, Q.DL, /*Depth=*/0, Q.AC, Q.CxtI, Q.DT))
+    return new ICmpInst(PredOut, Op0, Op1);
+
+  return nullptr;
+}
+
 /// Try to fold icmp (binop), X or icmp X, (binop).
 /// TODO: A large part of this logic is duplicated in InstSimplify's
 /// simplifyICmpWithBinOp(). We should be able to share that and avoid the code
@@ -4449,6 +4473,9 @@
                               ConstantExpr::getNeg(RHSC));
   }
 
+  if (Instruction * R = foldICmpXorXX(I, Q, *this))
+    return R;
+
   {
     // Try to remove shared multiplier from comparison:
     // X * Z u{lt/le/gt/ge}/eq/ne Y * Z


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