[InstCombine] Generalize foldAndOrOfICmpEqZeroAndICmp

[0xdc03]

Summary

This patch generalizes the fold implemented by foldAndOrOfICmpEqZeroAndICmp,
which are:

(icmp eq X, 0) | (icmp ult Other, X) -> (icmp ule Other, X-1)
(icmp ne X, 0) & (icmp uge Other, X) -> (icmp ugt Other, X-1)

to the following:

(icmp eq X, C) | (icmp ult Other, (X - C)) -> (icmp ule Other, (X - (C + 1)))
(icmp ne X, C) & (icmp uge Other, (X - C)) -> (icmp ugt Other, (X - (C + 1)))

The function foldAndOrOfICmpEqZeroAndICmp is also renamed to
foldAndOrOfICmpEqConstantAndICmp to reflect the changes.

Proofs: https://alive2.llvm.org/ce/z/yXGv6q

Fixes #63749.

[0xdc03]

• Rebase on top of tests: D154938

[nikic]

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

3002

Move this lower, not needed here yet.

3022

Create the constant directly from *CInt + 1, no need for CreateAdd.

llvm/test/Transforms/InstCombine/and-or-icmp-const-icmp.ll

27–28

Write this in canonical form (add -5) or drop the test if redundant with the next.

27–28

Not actually commuted. Grep for thwart complexity-based canonicalization in tests.

27–28

No need for separate commuted vector tests.

[0xdc03]

• Address reviewer comments
  • Remove unneeded variable C
  • Clean up tests

[0xdc03]

llvm/test/Transforms/InstCombine/and-or-icmp-const-icmp.ll

27–28

I was aiming for the signs to be opposite in them, dunno if that is necessary.

[nikic]

LGTM

[0xdc03]

• Fix failing test
• Rebase on top of updated tests

[nikic]

llvm/test/Transforms/InstCombine/and-or-icmp-const-icmp.ll

160

As you're using m_APIntAllowUndef now, I'd suggest to also add a "splat with undef" vector test like <i8 5, i8 undef> here.

[0xdc03]

• Address reviewer comment: Add an undef splat vector test

[nikic]

llvm/test/Transforms/InstCombine/and-or-icmp-const-icmp.ll

235

We should also have the variant with the undef on the add. Handling that one would need m_SpecificIntAllowUndef() as well.

[0xdc03]

• Address reviewer comment: Match undef on add as well

[0xdc03]

llvm/test/Transforms/InstCombine/and-or-icmp-const-icmp.ll

235

Done, though I'm just appending the test to this patch.

[nikic]

LGTM

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

if (Value *Cond = getSelectCondition(A, B, InvertFalseVal)) {
     Value *BitcastD = Builder.CreateBitCast(D, SelTy);
     Value *Select = Builder.CreateSelect(Cond, BitcastC, BitcastD);
     return Builder.CreateBitCast(Select, OrigType);
   }
 
   return nullptr;
 }
 
-// (icmp eq X, 0) | (icmp ult Other, X) -> (icmp ule Other, X-1)
-// (icmp ne X, 0) & (icmp uge Other, X) -> (icmp ugt Other, X-1)
-static Value *foldAndOrOfICmpEqZeroAndICmp(ICmpInst *LHS, ICmpInst *RHS,
+// (icmp eq X, C) | (icmp ult Other, (X - C)) -> (icmp ule Other, (X - (C + 1)))
+// (icmp ne X, C) & (icmp uge Other, (X - C)) -> (icmp ugt Other, (X - (C + 1)))
+static Value *foldAndOrOfICmpEqConstantAndICmp(ICmpInst *LHS, ICmpInst *RHS,
                                                bool IsAnd, bool IsLogical,
                                                IRBuilderBase &Builder) {
+  Value *LHS0 = LHS->getOperand(0);
+  Value *RHS0 = RHS->getOperand(0);
+  Value *RHS1 = RHS->getOperand(1);
+
   ICmpInst::Predicate LPred =
       IsAnd ? LHS->getInversePredicate() : LHS->getPredicate();
   ICmpInst::Predicate RPred =
       IsAnd ? RHS->getInversePredicate() : RHS->getPredicate();
-  Value *LHS0 = LHS->getOperand(0);
-  if (LPred != ICmpInst::ICMP_EQ || !match(LHS->getOperand(1), m_Zero()) ||
+
+  const APInt *CInt;
+  if (LPred != ICmpInst::ICMP_EQ ||
+      !match(LHS->getOperand(1), m_APIntAllowUndef(CInt)) ||
       !LHS0->getType()->isIntOrIntVectorTy() ||
       !(LHS->hasOneUse() || RHS->hasOneUse()))
     return nullptr;
 
+  auto MatchRHSOp = [LHS0, CInt](const Value *RHSOp) {
+    return match(RHSOp,
+                 m_Add(m_Specific(LHS0), m_SpecificIntAllowUndef(-*CInt))) ||
+           (CInt->isZero() && RHSOp == LHS0);
+  };
+
   Value *Other;
-  if (RPred == ICmpInst::ICMP_ULT && RHS->getOperand(1) == LHS0)
-    Other = RHS->getOperand(0);
-  else if (RPred == ICmpInst::ICMP_UGT && RHS->getOperand(0) == LHS0)
-    Other = RHS->getOperand(1);
+  if (RPred == ICmpInst::ICMP_ULT && MatchRHSOp(RHS1))
+    Other = RHS0;
+  else if (RPred == ICmpInst::ICMP_UGT && MatchRHSOp(RHS0))
+    Other = RHS1;
   else
     return nullptr;
 
   if (IsLogical)
     Other = Builder.CreateFreeze(Other);
+
   return Builder.CreateICmp(
       IsAnd ? ICmpInst::ICMP_ULT : ICmpInst::ICMP_UGE,
-      Builder.CreateAdd(LHS0, Constant::getAllOnesValue(LHS0->getType())),
+      Builder.CreateSub(LHS0, ConstantInt::get(LHS0->getType(), *CInt + 1)),
       Other);
 }
 
 /// Fold (icmp)&(icmp) or (icmp)|(icmp) if possible.
 /// If IsLogical is true, then the and/or is in select form and the transform
 /// must be poison-safe.
 Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
                                           Instruction &I, bool IsAnd,
                                           bool IsLogical) {
Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
 
   // handle (roughly):
   // (icmp ne (A & B), C) | (icmp ne (A & D), E)
   // (icmp eq (A & B), C) & (icmp eq (A & D), E)
   if (Value *V = foldLogOpOfMaskedICmps(LHS, RHS, IsAnd, IsLogical, Builder))
     return V;
 
   if (Value *V =
-          foldAndOrOfICmpEqZeroAndICmp(LHS, RHS, IsAnd, IsLogical, Builder))
+          foldAndOrOfICmpEqConstantAndICmp(LHS, RHS, IsAnd, IsLogical, Builder))
     return V;
   // We can treat logical like bitwise here, because both operands are used on
   // the LHS, and as such poison from both will propagate.
-  if (Value *V = foldAndOrOfICmpEqZeroAndICmp(RHS, LHS, IsAnd,
+  if (Value *V = foldAndOrOfICmpEqConstantAndICmp(RHS, LHS, IsAnd,
                                                   /*IsLogical*/ false, Builder))
     return V;
 
   if (Value *V =
           foldAndOrOfICmpsWithConstEq(LHS, RHS, IsAnd, IsLogical, Builder, Q))
     return V;
   // We can convert this case to bitwise and, because both operands are used
   // on the LHS, and as such poison from both will propagate.
   if (Value *V = foldAndOrOfICmpsWithConstEq(RHS, LHS, IsAnd,

llvm/test/Transforms/InstCombine/and-or-icmp-const-icmp.ll

 ; CHECK-NEXT:    [[OR:%.*]] = icmp uge i8 [[TMP1]], [[Y]]
 ; CHECK-NEXT:    ret i1 [[OR]]
 ;
   %c1 = icmp eq i8 %x, 0
   %c2 = icmp ugt i8 %x, %y
   %or = or i1 %c1, %c2
   ret i1 %or
 }
 
 define i1 @ne_basic_equal_5(i8 %x, i8 %y) {
 ; CHECK-LABEL: define i1 @ne_basic_equal_5
 ; CHECK-SAME: (i8 [[X:%.*]], i8 [[Y:%.*]]) {
-; CHECK-NEXT:    [[SUB:%.*]] = add i8 [[X]], -5
-; CHECK-NEXT:    [[C1:%.*]] = icmp ne i8 [[X]], 5
-; CHECK-NEXT:    [[C2:%.*]] = icmp ule i8 [[SUB]], [[Y]]
-; CHECK-NEXT:    [[AND:%.*]] = and i1 [[C1]], [[C2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[X]], -6
+; CHECK-NEXT:    [[AND:%.*]] = icmp ult i8 [[TMP1]], [[Y]]
 ; CHECK-NEXT:    ret i1 [[AND]]
 ;
   %sub = add i8 %x, -5
   %c1 = icmp ne i8 %x, 5
   %c2 = icmp ule i8 %sub, %y
   %and = and i1 %c1, %c2
   ret i1 %and
 }
 
 define i1 @eq_basic_equal_minus_1(i8 %x, i8 %y) {
 ; CHECK-LABEL: define i1 @eq_basic_equal_minus_1
 ; CHECK-SAME: (i8 [[X:%.*]], i8 [[Y:%.*]]) {
-; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[X]], 1
-; CHECK-NEXT:    [[C1:%.*]] = icmp eq i8 [[X]], -1
-; CHECK-NEXT:    [[C2:%.*]] = icmp ugt i8 [[ADD]], [[Y]]
-; CHECK-NEXT:    [[OR:%.*]] = or i1 [[C1]], [[C2]]
+; CHECK-NEXT:    [[OR:%.*]] = icmp uge i8 [[X]], [[Y]]
 ; CHECK-NEXT:    ret i1 [[OR]]
 ;
   %add = add i8 %x, 1
   %c1 = icmp eq i8 %x, -1
   %c2 = icmp ugt i8 %add, %y
   %or = or i1 %c1, %c2
   ret i1 %or
 }
 
 define i1 @ne_basic_equal_minus_7(i8 %x, i8 %y) {
 ; CHECK-LABEL: define i1 @ne_basic_equal_minus_7
 ; CHECK-SAME: (i8 [[X:%.*]], i8 [[Y:%.*]]) {
-; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[X]], 7
-; CHECK-NEXT:    [[C1:%.*]] = icmp ne i8 [[X]], -7
-; CHECK-NEXT:    [[C2:%.*]] = icmp ule i8 [[ADD]], [[Y]]
-; CHECK-NEXT:    [[AND:%.*]] = and i1 [[C1]], [[C2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[X]], 6
+; CHECK-NEXT:    [[AND:%.*]] = icmp ult i8 [[TMP1]], [[Y]]
 ; CHECK-NEXT:    ret i1 [[AND]]
 ;
   %add = add i8 %x, 7
   %c1 = icmp ne i8 %x, -7
   %c2 = icmp ule i8 %add, %y
   %and = and i1 %c1, %c2
   ret i1 %and
 }
;
   %c2 = icmp ugt <2 x i8> %x, %y
   %or = or <2 x i1> %c1, %c2
   ret <2 x i1> %or
 }
 
 define <2 x i1> @ne_vector_equal_5(<2 x i8> %x, <2 x i8> %y) {
 ; CHECK-LABEL: define <2 x i1> @ne_vector_equal_5
 ; CHECK-SAME: (<2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]]) {
-; CHECK-NEXT:    [[SUB:%.*]] = add <2 x i8> [[X]], <i8 -5, i8 -5>
-; CHECK-NEXT:    [[C1:%.*]] = icmp ne <2 x i8> [[X]], <i8 5, i8 5>
-; CHECK-NEXT:    [[C2:%.*]] = icmp ule <2 x i8> [[SUB]], [[Y]]
-; CHECK-NEXT:    [[AND:%.*]] = and <2 x i1> [[C1]], [[C2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add <2 x i8> [[X]], <i8 -6, i8 -6>
+; CHECK-NEXT:    [[AND:%.*]] = icmp ult <2 x i8> [[TMP1]], [[Y]]
 ; CHECK-NEXT:    ret <2 x i1> [[AND]]
 ;
   %sub = add <2 x i8> %x, <i8 -5, i8 -5>
   %c1 = icmp ne <2 x i8> %x, <i8 5, i8 5>
   %c2 = icmp ule <2 x i8> %sub, %y
   %and = and <2 x i1> %c1, %c2
   ret <2 x i1> %and
 }
 
 define <2 x i1> @eq_vector_equal_minus_1(<2 x i8> %x, <2 x i8> %y) {
 ; CHECK-LABEL: define <2 x i1> @eq_vector_equal_minus_1
 ; CHECK-SAME: (<2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]]) {
-; CHECK-NEXT:    [[ADD:%.*]] = add <2 x i8> [[X]], <i8 1, i8 1>
-; CHECK-NEXT:    [[C1:%.*]] = icmp eq <2 x i8> [[X]], <i8 -1, i8 -1>
-; CHECK-NEXT:    [[C2:%.*]] = icmp ugt <2 x i8> [[ADD]], [[Y]]
-; CHECK-NEXT:    [[OR:%.*]] = or <2 x i1> [[C1]], [[C2]]
+; CHECK-NEXT:    [[OR:%.*]] = icmp uge <2 x i8> [[X]], [[Y]]
 ; CHECK-NEXT:    ret <2 x i1> [[OR]]
 ;
   %add = add <2 x i8> %x, <i8 1, i8 1>
   %c1 = icmp eq <2 x i8> %x, <i8 -1, i8 -1>
   %c2 = icmp ugt <2 x i8> %add, %y
   %or = or <2 x i1> %c1, %c2
   ret <2 x i1> %or
 }
 
 define <2 x i1> @ne_vector_equal_minus_7(<2 x i8> %x, <2 x i8> %y) {
 ; CHECK-LABEL: define <2 x i1> @ne_vector_equal_minus_7
 ; CHECK-SAME: (<2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]]) {
-; CHECK-NEXT:    [[ADD:%.*]] = add <2 x i8> [[X]], <i8 7, i8 7>
-; CHECK-NEXT:    [[C1:%.*]] = icmp ne <2 x i8> [[X]], <i8 -7, i8 -7>
-; CHECK-NEXT:    [[C2:%.*]] = icmp ule <2 x i8> [[ADD]], [[Y]]
-; CHECK-NEXT:    [[AND:%.*]] = and <2 x i1> [[C1]], [[C2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add <2 x i8> [[X]], <i8 6, i8 6>
+; CHECK-NEXT:    [[AND:%.*]] = icmp ult <2 x i8> [[TMP1]], [[Y]]
 ; CHECK-NEXT:    ret <2 x i1> [[AND]]
 ;
   %add = add <2 x i8> %x, <i8 7, i8 7>
   %c1 = icmp ne <2 x i8> %x, <i8 -7, i8 -7>
   %c2 = icmp ule <2 x i8> %add, %y
   %and = and <2 x i1> %c1, %c2
   ret <2 x i1> %and
 }
;
   %c2 = icmp ule <2 x i8> %add, %y
   %and = and <2 x i1> %c1, %c2
   ret <2 x i1> %and
 }
 
 ; ==============================================================================
 ; Tests with undef
 ; ==============================================================================
-define <2 x i1> @eq_vector_undef(<2 x i8> %x, <2 x i8> %y) {
-; CHECK-LABEL: define <2 x i1> @eq_vector_undef
+define <2 x i1> @eq_vector_undef_icmp(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: define <2 x i1> @eq_vector_undef_icmp
 ; CHECK-SAME: (<2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]]) {
-; CHECK-NEXT:    [[SUB:%.*]] = add <2 x i8> [[X]], <i8 -5, i8 -5>
-; CHECK-NEXT:    [[C1:%.*]] = icmp eq <2 x i8> [[X]], <i8 5, i8 undef>
-; CHECK-NEXT:    [[C2:%.*]] = icmp ugt <2 x i8> [[SUB]], [[Y]]
-; CHECK-NEXT:    [[OR:%.*]] = or <2 x i1> [[C1]], [[C2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = add <2 x i8> [[X]], <i8 -6, i8 -6>
+; CHECK-NEXT:    [[OR:%.*]] = icmp uge <2 x i8> [[TMP1]], [[Y]]
 ; CHECK-NEXT:    ret <2 x i1> [[OR]]
 ;
   %sub = add <2 x i8> %x, <i8 -5, i8 -5>
   %c1 = icmp eq <2 x i8> %x, <i8 5, i8 undef>
   %c2 = icmp ugt <2 x i8> %sub, %y
   %or = or <2 x i1> %c1, %c2
   ret <2 x i1> %or
 }
 
+define <2 x i1> @eq_vector_undef_add(<2 x i8> %x, <2 x i8> %y) {
+; CHECK-LABEL: define <2 x i1> @eq_vector_undef_add
+; CHECK-SAME: (<2 x i8> [[X:%.*]], <2 x i8> [[Y:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = add <2 x i8> [[X]], <i8 -6, i8 -6>
+; CHECK-NEXT:    [[OR:%.*]] = icmp uge <2 x i8> [[TMP1]], [[Y]]
+; CHECK-NEXT:    ret <2 x i1> [[OR]]
+;
+  %sub = add <2 x i8> %x, <i8 -5, i8 undef>
+  %c1 = icmp eq <2 x i8> %x, <i8 5, i8 5>
+  %c2 = icmp ugt <2 x i8> %sub, %y
+  %or = or <2 x i1> %c1, %c2
+  ret <2 x i1> %or
+}
+
 ; ==============================================================================
 ; Tests with values commuted
 ; ==============================================================================
 define i1 @eq_commuted(i8 %x, i8 %py) {
 ; CHECK-LABEL: define i1 @eq_commuted
 ; CHECK-SAME: (i8 [[X:%.*]], i8 [[PY:%.*]]) {
 ; CHECK-NEXT:    [[Y:%.*]] = sdiv i8 43, [[PY]]
 ; CHECK-NEXT:    [[TMP1:%.*]] = add i8 [[X]], -1
 ; CHECK-NEXT:    [[OR:%.*]] = icmp uge i8 [[TMP1]], [[Y]]
 ; CHECK-NEXT:    ret i1 [[OR]]
 ;
   %y = sdiv i8 43, %py ; thwart complexity-based canonicalization
   %c1 = icmp eq i8 %x, 0
   %c2 = icmp ult i8 %y, %x
   %or = or i1 %c1, %c2
   ret i1 %or
 }
 
 define i1 @ne_commuted_equal_minus_1(i8 %x, i8 %py) {
 ; CHECK-LABEL: define i1 @ne_commuted_equal_minus_1
 ; CHECK-SAME: (i8 [[X:%.*]], i8 [[PY:%.*]]) {
 ; CHECK-NEXT:    [[Y:%.*]] = sdiv i8 42, [[PY]]
-; CHECK-NEXT:    [[ADD:%.*]] = add i8 [[X]], 1
-; CHECK-NEXT:    [[C1:%.*]] = icmp ne i8 [[X]], -1
-; CHECK-NEXT:    [[C2:%.*]] = icmp uge i8 [[Y]], [[ADD]]
-; CHECK-NEXT:    [[AND:%.*]] = and i1 [[C1]], [[C2]]
+; CHECK-NEXT:    [[AND:%.*]] = icmp ugt i8 [[Y]], [[X]]
 ; CHECK-NEXT:    ret i1 [[AND]]
 ;
   %y = sdiv i8 42, %py ; thwart complexity-based canonicalization
   %add = add i8 %x, 1
   %c1 = icmp ne i8 %x, -1
   %c2 = icmp uge i8 %y, %add
   %and = and i1 %c1, %c2
   ret i1 %and
 }
 
 declare void @use(i1)