[InstCombine] Try to reuse constant from select in leading comparison

[lebedev.ri]

Summary

If we have e.g.:

%t = icmp ult i32 %x, 65536
%r = select i1 %t, i32 %y, i32 65535

the constants 65535 and 65536 are suspiciously close.
We could perform a transformation to deduplicate them:

Name: ult
%t = icmp ult i32 %x, 65536
%r = select i1 %t, i32 %y, i32 65535
  =>
%t.inv = icmp ugt i32 %x, 65535
%r = select i1 %t.inv, i32 65535, i32 %y

https://rise4fun.com/Alive/avb

While this may seem esoteric, this should certainly be good for vectors
(less constant pool usage) and for opt-for-size - need to have only one constant.

But the real fun part here is that it allows further transformation,
in particular it finishes cleaning up the clamp folding,
see e.g. canonicalize-clamp-with-select-of-constant-threshold-pattern.ll.
We start with e.g.

%dont_need_to_clamp_positive = icmp sle i32 %X, 32767
%dont_need_to_clamp_negative = icmp sge i32 %X, -32768
%clamp_limit = select i1 %dont_need_to_clamp_positive, i32 -32768, i32 32767
%dont_need_to_clamp = and i1 %dont_need_to_clamp_positive, %dont_need_to_clamp_negative
%R = select i1 %dont_need_to_clamp, i32 %X, i32 %clamp_limit

without this patch we currently produce

%1 = icmp slt i32 %X, 32768
%2 = icmp sgt i32 %X, -32768
%3 = select i1 %2, i32 %X, i32 -32768
%R = select i1 %1, i32 %3, i32 32767

which isn't really a clamp - both comparisons are performed on the original value,
this patch changes it into

%1.inv = icmp sgt i32 %X, 32767
%2 = icmp sgt i32 %X, -32768
%3 = select i1 %2, i32 %X, i32 -32768
%R = select i1 %1.inv, i32 32767, i32 %3

and then the magic happens! Some further transform finishes polishing it and we finally get:

%t1 = icmp sgt i32 %X, -32768
%t2 = select i1 %t1, i32 %X, i32 -32768
%t3 = icmp slt i32 %t2, 32767
%R = select i1 %t3, i32 %t2, i32 32767

which is beautiful and just what we want.

Proofs for getFlippedStrictnessPredicateAndConstant() for de-canonicalization:
https://rise4fun.com/Alive/THl
Proofs for the fold itself: https://rise4fun.com/Alive/THl

[lebedev.ri]

llvm/test/Transforms/InstCombine/unrecognized_three-way-comparison.ll

96–110

This is clearly a regression.
I suppose it means this fold happens before some other fold that used to happen,
and that fold does not know how to deal with the new pattern.
I'd prefer to look into this afterwards.

[xbolva00]

llvm/test/Transforms/InstCombine/reuse-constant-from-select-in-icmp.ll

194

Tests:

%r = select i1 %t, i32 65535, i32 65536

%r = select i1 %t, i32 65535, i32 65537

?

[lebedev.ri]

Revisited test coverage, NFC.

[xbolva00]

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

1350

test for this line?

[xbolva00]

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

1350

(are all swapValues in LLVM codebase followed byt swapProfMetadata? no bugs?)

[xbolva00]

llvm/test/Transforms/InstCombine/reuse-constant-from-select-in-icmp.ll

336

Oh ignore me

[lebedev.ri]

bump

[xbolva00]

llvm/test/Transforms/InstCombine/unrecognized_three-way-comparison.ll

96–110

No status update here? Or did you find what is broken?

Patch looks fine I think, but this worries me - we may realize later that the root cause of regression is possibly nontrivial thing which could lead us to rever this one. (and wasted time).

[lebedev.ri]

llvm/test/Transforms/InstCombine/unrecognized_three-way-comparison.ll

96–110

Added some tests in rL369667.
Whatever handles this is "simply" ignorant about commutativity.

[xbolva00]

I like idea here and patch seems generally fine.

@nikic, @dmgreen, @spatel are probably interested to check this too.

llvm/test/Transforms/InstCombine/unrecognized_three-way-comparison.ll

96–110

Ok, thanks for info.

(Not a patch blocker)

[lebedev.ri]

llvm/test/Transforms/InstCombine/unrecognized_three-way-comparison.ll

96–110

The problems appear to begin in InstCombiner::foldICmpSelectConstant(),
which uses InstCombiner::matchThreeWayIntCompare():

bool InstCombiner::matchThreeWayIntCompare(SelectInst *SI, Value *&LHS,
                                           Value *&RHS, ConstantInt *&Less,
                                           ConstantInt *&Equal,
                                           ConstantInt *&Greater) {
  // TODO: Generalize this to work with other comparison idioms or ensure
  // they get canonicalized into this form.

  // select i1 (a == b), i32 Equal, i32 (select i1 (a < b), i32 Less, i32
  // Greater), where Equal, Less and Greater are placeholders for any three
  // constants.

Not unsurprisingly, it does not handle any other pattern :/

[lebedev.ri]

Rebased, posted D66607 to adress regression that this patch exposes.

[lebedev.ri]

Rebased, NFC.

[spatel]

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

1297–1300

Is this check to avoid an infinite loop or some other reason?

It seems strange that we need only that specific check. Maybe this should re-use this code from InstCombineCompares.cpp:

static bool isSignTest(ICmpInst::Predicate &Pred, const APInt &C)

or llvm::decomposeBitTestICmp()?

If I'm seeing it correctly, we would transform this case (and that's ok?):

define i32 @x_is_not_negative(i32 %x, i32 %y) {
  %t = icmp sgt i32 %x, -1
  %r = select i1 %t, i32 0, i32 %y
  ret i32 %r
}

[lebedev.ri]

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

1297–1300

Is this check to avoid an infinite loop?

Initially - yes.
But weird, if i drop that check the original testcase no longer hangs.

[lebedev.ri]

Drop strange blacklisting of some specific sign-bit-like-check - initially i was observing some endless combine loop,
but it no longer happens neither on the specific test nor on check-llvm-transforms nor on test-suite.
So i don't know what it was.

[spatel]

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

1299

This seems like it would be generally useful as a Constant query function, so it'd be nice to move it over to Constant.h either before or after this commit.

1320

'Check' is a bit too vague. 'MatchesSelectValue'?

1329

Remove 'Else, lets' - the sentence reads fine to me as:

// Check the constant we'd have with flipped-strictness predicate.

llvm/test/Transforms/InstCombine/unrecognized_three-way-comparison.ll

96–110

Does D66607 catch this, or am I inverting the relationship of the patches?

[lebedev.ri]

Thanks for taking a look!
Addressed review nits.

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

1299

Indeed, will move afterwards.

1320

Oh, nice one!

llvm/test/Transforms/InstCombine/unrecognized_three-way-comparison.ll

96–110

D66607 does fix regressions in this file, yes.

[spatel]

LGTM

[lebedev.ri]

In D66232#1643528, @spatel wrote:

LGTM

Thank you for the review!

llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp

Instruction *InstCombiner::foldICmpUsingKnownBits(ICmpInst &I) {
 
   return nullptr;
 }
 
 llvm::Optional<std::pair<CmpInst::Predicate, Constant *>>
 llvm::getFlippedStrictnessPredicateAndConstant(CmpInst::Predicate Pred,
                                                Constant *C) {
   assert(ICmpInst::isRelational(Pred) && ICmpInst::isIntPredicate(Pred) &&
-         !isCanonicalPredicate(Pred) &&
-         "Only for non-canonical relational integer predicates.");
+         "Only for relational integer predicates.");
 
-  // Check if the constant operand can be safely incremented/decremented without
-  // overflowing/underflowing. For scalars, SimplifyICmpInst should have already
-  // handled the edge cases for us, so we just assert on them.
-  // For vectors, we must handle the edge cases.
   Type *Type = C->getType();
   bool IsSigned = ICmpInst::isSigned(Pred);
-  bool IsLE = (Pred == ICmpInst::ICMP_SLE || Pred == ICmpInst::ICMP_ULE);
-  auto *CI = dyn_cast<ConstantInt>(C);
-  if (CI) {
+
+  CmpInst::Predicate UnsignedPred = ICmpInst::getUnsignedPredicate(Pred);
+  bool WillIncrement =
+      UnsignedPred == ICmpInst::ICMP_ULE || UnsignedPred == ICmpInst::ICMP_UGT;
+
+  // Check if the constant operand can be safely incremented/decremented
+  // without overflowing/underflowing.
+  auto ConstantIsOk = [WillIncrement, IsSigned](ConstantInt *C) {
+    return WillIncrement ? !C->isMaxValue(IsSigned) : !C->isMinValue(IsSigned);
+  };
+
+  // For scalars, SimplifyICmpInst should have already handled
+  // the edge cases for us, so we just assert on them.
+  // For vectors, we must handle the edge cases.
+  if (auto *CI = dyn_cast<ConstantInt>(C)) {
     // A <= MAX -> TRUE ; A >= MIN -> TRUE
-    assert(IsLE ? !CI->isMaxValue(IsSigned) : !CI->isMinValue(IsSigned));
+    assert(ConstantIsOk(CI));
   } else if (Type->isVectorTy()) {
     // TODO? If the edge cases for vectors were guaranteed to be handled as they
     // are for scalar, we could remove the min/max checks. However, to do that,
     // we would have to use insertelement/shufflevector to replace edge values.
     unsigned NumElts = Type->getVectorNumElements();
     for (unsigned i = 0; i != NumElts; ++i) {
       Constant *Elt = C->getAggregateElement(i);
       if (!Elt)
         return llvm::None;
 
       if (isa<UndefValue>(Elt))
         continue;
 
       // Bail out if we can't determine if this constant is min/max or if we
       // know that this constant is min/max.
       auto *CI = dyn_cast<ConstantInt>(Elt);
-      if (!CI || (IsLE ? CI->isMaxValue(IsSigned) : CI->isMinValue(IsSigned)))
+      if (!CI || !ConstantIsOk(CI))
         return llvm::None;
     }
   } else {
     // ConstantExpr?
     return llvm::None;
   }
 
   CmpInst::Predicate NewPred = CmpInst::getFlippedStrictnessPredicate(Pred);
 
   // Increment or decrement the constant.
-  Constant *OneOrNegOne = ConstantInt::get(Type, IsLE ? 1 : -1, true);
+  Constant *OneOrNegOne = ConstantInt::get(Type, WillIncrement ? 1 : -1, true);
   Constant *NewC = ConstantExpr::getAdd(C, OneOrNegOne);
 
   return std::make_pair(NewPred, NewC);
 }
 
 /// If we have an icmp le or icmp ge instruction with a constant operand, turn
 /// it into the appropriate icmp lt or icmp gt instruction. This transform
 /// allows them to be folded in visitICmpInst.

llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp

static Instruction *canonicalizeClampLike(SelectInst &Sel0, ICmpInst &Cmp0,
   Value *MaybeReplacedLow =
       Builder.CreateSelect(ShouldReplaceLow, ReplacementLow, X);
   Instruction *MaybeReplacedHigh =
       SelectInst::Create(ShouldReplaceHigh, ReplacementHigh, MaybeReplacedLow);
 
   return MaybeReplacedHigh;
 }
 
+// If we have
+//  %cmp = icmp [canonical predicate] i32 %x, C0
+//  %r = select i1 %cmp, i32 %y, i32 C1
+// Where C0 != C1 and %x may be different from %y, see if the constant that we
+// will have if we flip the strictness of the predicate (i.e. without changing
+// the result) is identical to the C1 in select. If it matches we can change
+// original comparison to one with swapped predicate, reuse the constant,
+// and swap the hands of select.
+static Instruction *
+tryToReuseConstantFromSelectInComparison(SelectInst &Sel, ICmpInst &Cmp,
+                                         InstCombiner::BuilderTy &Builder) {
+  ICmpInst::Predicate Pred;
+  Value *X;
+  Constant *C0;
+  if (!match(&Cmp, m_OneUse(m_ICmp(
+                       Pred, m_Value(X),
+                       m_CombineAnd(m_AnyIntegralConstant(), m_Constant(C0))))))
+    return nullptr;
+
+  // If comparison predicate is non-relational, we won't be able to do anything.
+  if (ICmpInst::isEquality(Pred))
+    return nullptr;
+
+  // If comparison predicate is non-canonical, then we certainly won't be able
+  // to make it canonical; canonicalizeCmpWithConstant() already tried.
+  if (!isCanonicalPredicate(Pred))
+    return nullptr;
+
+  // If the [input] type of comparison and select type are different, lets abort
+  // for now. We could try to compare constants with trunc/[zs]ext though.
+  if (C0->getType() != Sel.getType())
+    return nullptr;
+
+  // FIXME: are there any magic icmp predicate+constant pairs we must not touch?
+
+  auto ConstantsAreElementWiseEqual = [](Constant *Cx, Value *Y) {
+    // Are they fully identical?
+    if (Cx == Y)
+      return true;
+    // They may still be identical element-wise (if they have `undef`s).
+    auto *Cy = dyn_cast<Constant>(Y);
+    if (!Cy)
+      return false;
+    return match(ConstantExpr::getICmp(ICmpInst::Predicate::ICMP_EQ, Cx, Cy),
+                 m_One());
+  };
+
+  Value *SelVal0, *SelVal1; // We do not care which one is from where.
+  match(&Sel, m_Select(m_Value(), m_Value(SelVal0), m_Value(SelVal1)));
+  // At least one of these values we are selecting between must be a constant
+  // else we'll never succeed.
+  if (!match(SelVal0, m_AnyIntegralConstant()) &&
+      !match(SelVal1, m_AnyIntegralConstant()))
+    return nullptr;
+
+  // Does this constant C match any of the `select` values?
+  auto MatchesSelectValue = [ConstantsAreElementWiseEqual, SelVal0,
+                             SelVal1](Constant *C) {
+    return ConstantsAreElementWiseEqual(C, SelVal0) ||
+           ConstantsAreElementWiseEqual(C, SelVal1);
+  };
+
+  // If C0 *already* matches true/false value of select, we are done.
+  if (MatchesSelectValue(C0))
+    return nullptr;
+
+  // Check the constant we'd have with flipped-strictness predicate.
+  auto FlippedStrictness = getFlippedStrictnessPredicateAndConstant(Pred, C0);
+  if (!FlippedStrictness)
+    return nullptr;
+
+  // If said constant doesn't match either, then there is no hope,
+  if (!MatchesSelectValue(FlippedStrictness->second))
+    return nullptr;
+
+  // It matched! Lets insert the new comparison just before select.
+  InstCombiner::BuilderTy::InsertPointGuard Guard(Builder);
+  Builder.SetInsertPoint(&Sel);
+
+  Pred = ICmpInst::getSwappedPredicate(Pred); // Yes, swapped.
+  Value *NewCmp = Builder.CreateICmp(Pred, X, FlippedStrictness->second,
+                                     Cmp.getName() + ".inv");
+  Sel.setCondition(NewCmp);
+  Sel.swapValues();
+  Sel.swapProfMetadata();
+
+  return &Sel;
+}
+
 /// Visit a SelectInst that has an ICmpInst as its first operand.
 Instruction *InstCombiner::foldSelectInstWithICmp(SelectInst &SI,
                                                   ICmpInst *ICI) {
   if (Value *V = foldSelectValueEquivalence(SI, *ICI, SQ))
     return replaceInstUsesWith(SI, V);
 
   if (Instruction *NewSel = canonicalizeMinMaxWithConstant(SI, *ICI, Builder))
     return NewSel;
 
   if (Instruction *NewAbs = canonicalizeAbsNabs(SI, *ICI, Builder))
     return NewAbs;
 
   if (Instruction *NewAbs = canonicalizeClampLike(SI, *ICI, Builder))
     return NewAbs;
 
+  if (Instruction *NewSel =
+          tryToReuseConstantFromSelectInComparison(SI, *ICI, Builder))
+    return NewSel;
+
   bool Changed = adjustMinMax(SI, *ICI);
 
   if (Value *V = foldSelectICmpAnd(SI, ICI, Builder))
     return replaceInstUsesWith(SI, V);
 
   // NOTE: if we wanted to, this is where to detect integer MIN/MAX
   Value *TrueVal = SI.getTrueValue();
   Value *FalseVal = SI.getFalseValue();

llvm/test/Transforms/InstCombine/canonicalize-clamp-with-select-of-constant-threshold-pattern.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -instcombine -S | FileCheck %s
 
 ; These patterns are all just traditional clamp pattern.
 ; But they are not canonical, the and/or/xor is more canonically represented
 ; as an add+icmp.
 
 define i32 @t0_select_cond_and_v0(i32 %X) {
 ; CHECK-LABEL: @t0_select_cond_and_v0(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[X]], -32768
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[X]], i32 -32768
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP1]], i32 [[TMP3]], i32 32767
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i32 [[X:%.*]], -32768
+; CHECK-NEXT:    [[TMP2:%.*]] = select i1 [[TMP1]], i32 [[X]], i32 -32768
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp slt i32 [[TMP2]], 32767
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP3]], i32 [[TMP2]], i32 32767
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %dont_need_to_clamp_positive = icmp sle i32 %X, 32767
   %dont_need_to_clamp_negative = icmp sge i32 %X, -32768
   %clamp_limit = select i1 %dont_need_to_clamp_positive, i32 -32768, i32 32767
   %dont_need_to_clamp = and i1 %dont_need_to_clamp_positive, %dont_need_to_clamp_negative
   %R = select i1 %dont_need_to_clamp, i32 %X, i32 %clamp_limit
   ret i32 %R
 }
 define i32 @t1_select_cond_and_v1(i32 %X) {
 ; CHECK-LABEL: @t1_select_cond_and_v1(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[X]], -32768
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[X]], i32 -32768
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP1]], i32 [[TMP3]], i32 32767
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i32 [[X:%.*]], -32768
+; CHECK-NEXT:    [[TMP2:%.*]] = select i1 [[TMP1]], i32 [[X]], i32 -32768
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp slt i32 [[TMP2]], 32767
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP3]], i32 [[TMP2]], i32 32767
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %dont_need_to_clamp_positive = icmp sle i32 %X, 32767
   %dont_need_to_clamp_negative = icmp sge i32 %X, -32768
   %clamp_limit = select i1 %dont_need_to_clamp_negative, i32 32767, i32 -32768
   %dont_need_to_clamp = and i1 %dont_need_to_clamp_positive, %dont_need_to_clamp_negative
   %R = select i1 %dont_need_to_clamp, i32 %X, i32 %clamp_limit
   ret i32 %R
 }
 
 ;-------------------------------------------------------------------------------
 
 define i32 @t2_select_cond_or_v0(i32 %X) {
 ; CHECK-LABEL: @t2_select_cond_or_v0(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[X]], -32768
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[X]], i32 -32768
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP1]], i32 [[TMP3]], i32 32767
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i32 [[X:%.*]], -32768
+; CHECK-NEXT:    [[TMP2:%.*]] = select i1 [[TMP1]], i32 [[X]], i32 -32768
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp slt i32 [[TMP2]], 32767
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP3]], i32 [[TMP2]], i32 32767
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %need_to_clamp_positive = icmp sgt i32 %X, 32767
   %need_to_clamp_negative = icmp slt i32 %X, -32768
   %clamp_limit = select i1 %need_to_clamp_positive, i32 32767, i32 -32768
   %need_to_clamp = or i1 %need_to_clamp_positive, %need_to_clamp_negative
   %R = select i1 %need_to_clamp, i32 %clamp_limit, i32 %X
   ret i32 %R
 }
 define i32 @t3_select_cond_or_v1(i32 %X) {
 ; CHECK-LABEL: @t3_select_cond_or_v1(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[X]], -32768
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[X]], i32 -32768
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP1]], i32 [[TMP3]], i32 32767
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp sgt i32 [[X:%.*]], -32768
+; CHECK-NEXT:    [[TMP2:%.*]] = select i1 [[TMP1]], i32 [[X]], i32 -32768
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp slt i32 [[TMP2]], 32767
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP3]], i32 [[TMP2]], i32 32767
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %need_to_clamp_positive = icmp sgt i32 %X, 32767
   %need_to_clamp_negative = icmp slt i32 %X, -32768
   %clamp_limit = select i1 %need_to_clamp_negative, i32 -32768, i32 32767
   %need_to_clamp = or i1 %need_to_clamp_positive, %need_to_clamp_negative
   %R = select i1 %need_to_clamp, i32 %clamp_limit, i32 %X
   ret i32 %R
 }
 
 ;-------------------------------------------------------------------------------
 
 define i32 @t4_select_cond_xor_v0(i32 %X) {
 ; CHECK-LABEL: @t4_select_cond_xor_v0(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[X]], -32768
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[X]], i32 -32768
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP1]], i32 [[TMP3]], i32 32767
+; CHECK-NEXT:    [[DOTINV1:%.*]] = icmp sgt i32 [[X:%.*]], -32768
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[DOTINV1]], i32 [[X]], i32 -32768
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp slt i32 [[TMP1]], 32767
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP2]], i32 [[TMP1]], i32 32767
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %need_to_clamp_positive = icmp sgt i32 %X, 32767
   %dont_need_to_clamp_negative = icmp sgt i32 %X, -32768
   %clamp_limit = select i1 %need_to_clamp_positive, i32 32767, i32 -32768
   %dont_need_to_clamp = xor i1 %need_to_clamp_positive, %dont_need_to_clamp_negative
   %R = select i1 %dont_need_to_clamp, i32 %X, i32 %clamp_limit
   ret i32 %R
 }
 define i32 @t4_select_cond_xor_v1(i32 %X) {
 ; CHECK-LABEL: @t4_select_cond_xor_v1(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[X]], -32768
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[X]], i32 -32768
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP1]], i32 [[TMP3]], i32 32767
+; CHECK-NEXT:    [[DOTINV1:%.*]] = icmp sgt i32 [[X:%.*]], -32768
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[DOTINV1]], i32 [[X]], i32 -32768
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp slt i32 [[TMP1]], 32767
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP2]], i32 [[TMP1]], i32 32767
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %need_to_clamp_positive = icmp sgt i32 %X, 32767
   %dont_need_to_clamp_negative = icmp sgt i32 %X, -32768
   %clamp_limit = select i1 %dont_need_to_clamp_negative, i32 32767, i32 -32768
   %dont_need_to_clamp = xor i1 %need_to_clamp_positive, %dont_need_to_clamp_negative
   %R = select i1 %dont_need_to_clamp, i32 %X, i32 %clamp_limit
   ret i32 %R
 }
 
 define i32 @t5_select_cond_xor_v2(i32 %X) {
 ; CHECK-LABEL: @t5_select_cond_xor_v2(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[X]], -32768
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[X]], i32 -32768
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP1]], i32 [[TMP3]], i32 32767
+; CHECK-NEXT:    [[DOTINV1:%.*]] = icmp sgt i32 [[X:%.*]], -32768
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[DOTINV1]], i32 [[X]], i32 -32768
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp slt i32 [[TMP1]], 32767
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP2]], i32 [[TMP1]], i32 32767
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %dont_need_to_clamp_positive = icmp sle i32 %X, 32767
   %need_to_clamp_negative = icmp sle i32 %X, -32768
   %clamp_limit = select i1 %need_to_clamp_negative, i32 -32768, i32 32767
   %dont_need_to_clamp = xor i1 %dont_need_to_clamp_positive, %need_to_clamp_negative
   %R = select i1 %dont_need_to_clamp, i32 %X, i32 %clamp_limit
   ret i32 %R
 }
 define i32 @t5_select_cond_xor_v3(i32 %X) {
 ; CHECK-LABEL: @t5_select_cond_xor_v3(
-; CHECK-NEXT:    [[TMP1:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[X]], -32768
-; CHECK-NEXT:    [[TMP3:%.*]] = select i1 [[TMP2]], i32 [[X]], i32 -32768
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP1]], i32 [[TMP3]], i32 32767
+; CHECK-NEXT:    [[DOTINV1:%.*]] = icmp sgt i32 [[X:%.*]], -32768
+; CHECK-NEXT:    [[TMP1:%.*]] = select i1 [[DOTINV1]], i32 [[X]], i32 -32768
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp slt i32 [[TMP1]], 32767
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[TMP2]], i32 [[TMP1]], i32 32767
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %dont_need_to_clamp_positive = icmp sle i32 %X, 32767
   %need_to_clamp_negative = icmp sle i32 %X, -32768
   %clamp_limit = select i1 %dont_need_to_clamp_positive, i32 -32768, i32 32767
   %dont_need_to_clamp = xor i1 %dont_need_to_clamp_positive, %need_to_clamp_negative
   %R = select i1 %dont_need_to_clamp, i32 %X, i32 %clamp_limit
   ret i32 %R
 }

llvm/test/Transforms/InstCombine/reuse-constant-from-select-in-icmp.ll

 ;------------------------------------------------------------------------------;
 ; Canonical scalar predicates
 ;------------------------------------------------------------------------------;
 
 !0 = !{!"branch_weights", i32 2000, i32 1}
 
 define i32 @p0_ult_65536(i32 %x, i32 %y) {
 ; CHECK-LABEL: @p0_ult_65536(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult i32 [[X:%.*]], 65536
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 [[Y:%.*]], i32 65535, !prof !0
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt i32 [[X:%.*]], 65535
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 65535, i32 [[Y:%.*]], !prof !0
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp ult i32 %x, 65536
   %r = select i1 %t, i32 %y, i32 65535, !prof !0
   ret i32 %r
 }
 define i32 @p1_ugt(i32 %x, i32 %y) {
 ; CHECK-LABEL: @p1_ugt(
-; CHECK-NEXT:    [[T:%.*]] = icmp ugt i32 [[X:%.*]], 65534
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 [[Y:%.*]], i32 65535
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ult i32 [[X:%.*]], 65535
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 65535, i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp ugt i32 %x, 65534
   %r = select i1 %t, i32 %y, i32 65535
   ret i32 %r
 }
 define i32 @p2_slt_65536(i32 %x, i32 %y) {
 ; CHECK-LABEL: @p2_slt_65536(
-; CHECK-NEXT:    [[T:%.*]] = icmp slt i32 [[X:%.*]], 65536
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 [[Y:%.*]], i32 65535
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp sgt i32 [[X:%.*]], 65535
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 65535, i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp slt i32 %x, 65536
   %r = select i1 %t, i32 %y, i32 65535
   ret i32 %r
 }
 define i32 @p3_sgt(i32 %x, i32 %y) {
 ; CHECK-LABEL: @p3_sgt(
-; CHECK-NEXT:    [[T:%.*]] = icmp sgt i32 [[X:%.*]], 65534
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 [[Y:%.*]], i32 65535
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp slt i32 [[X:%.*]], 65535
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 65535, i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp sgt i32 %x, 65534
   %r = select i1 %t, i32 %y, i32 65535
   ret i32 %r
 }
 
 ;------------------------------------------------------------------------------;
 ; Vectors
 ;------------------------------------------------------------------------------;
 
 define <2 x i32> @p4_vec_splat_ult_65536(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @p4_vec_splat_ult_65536(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult <2 x i32> [[X:%.*]], <i32 65536, i32 65536>
-; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T]], <2 x i32> [[Y:%.*]], <2 x i32> <i32 65535, i32 65535>
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 65535>
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 65535>, <2 x i32> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %t = icmp ult <2 x i32> %x, <i32 65536, i32 65536>
   %r = select <2 x i1> %t, <2 x i32> %y, <2 x i32> <i32 65535, i32 65535>
   ret <2 x i32> %r
 }
 define <2 x i32> @p5_vec_splat_ugt(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @p5_vec_splat_ugt(
-; CHECK-NEXT:    [[T:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65534, i32 65534>
-; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T]], <2 x i32> [[Y:%.*]], <2 x i32> <i32 65535, i32 65535>
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ult <2 x i32> [[X:%.*]], <i32 65535, i32 65535>
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 65535>, <2 x i32> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %t = icmp ugt <2 x i32> %x, <i32 65534, i32 65534>
   %r = select <2 x i1> %t, <2 x i32> %y, <2 x i32> <i32 65535, i32 65535>
   ret <2 x i32> %r
 }
 define <2 x i32> @p6_vec_splat_slt_65536(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @p6_vec_splat_slt_65536(
-; CHECK-NEXT:    [[T:%.*]] = icmp slt <2 x i32> [[X:%.*]], <i32 65536, i32 65536>
-; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T]], <2 x i32> [[Y:%.*]], <2 x i32> <i32 65535, i32 65535>
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp sgt <2 x i32> [[X:%.*]], <i32 65535, i32 65535>
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 65535>, <2 x i32> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %t = icmp slt <2 x i32> %x, <i32 65536, i32 65536>
   %r = select <2 x i1> %t, <2 x i32> %y, <2 x i32> <i32 65535, i32 65535>
   ret <2 x i32> %r
 }
 define <2 x i32> @p7_vec_splat_sgt(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @p7_vec_splat_sgt(
-; CHECK-NEXT:    [[T:%.*]] = icmp sgt <2 x i32> [[X:%.*]], <i32 65534, i32 65534>
-; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T]], <2 x i32> [[Y:%.*]], <2 x i32> <i32 65535, i32 65535>
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp slt <2 x i32> [[X:%.*]], <i32 65535, i32 65535>
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 65535>, <2 x i32> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %t = icmp sgt <2 x i32> %x, <i32 65534, i32 65534>
   %r = select <2 x i1> %t, <2 x i32> %y, <2 x i32> <i32 65535, i32 65535>
   ret <2 x i32> %r
 }
 
 ; Vectors with undef
 
 define <2 x i32> @p8_vec_nonsplat_undef0(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @p8_vec_nonsplat_undef0(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult <2 x i32> [[X:%.*]], <i32 65536, i32 undef>
-; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T]], <2 x i32> [[Y:%.*]], <2 x i32> <i32 65535, i32 65535>
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 undef>
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 65535>, <2 x i32> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %t = icmp ult <2 x i32> %x, <i32 65536, i32 undef>
   %r = select <2 x i1> %t, <2 x i32> %y, <2 x i32> <i32 65535, i32 65535>
   ret <2 x i32> %r
 }
 define <2 x i32> @p9_vec_nonsplat_undef1(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @p9_vec_nonsplat_undef1(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult <2 x i32> [[X:%.*]], <i32 65536, i32 65536>
-; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T]], <2 x i32> [[Y:%.*]], <2 x i32> <i32 65535, i32 undef>
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 65535>
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 undef>, <2 x i32> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %t = icmp ult <2 x i32> %x, <i32 65536, i32 65536>
   %r = select <2 x i1> %t, <2 x i32> %y, <2 x i32> <i32 65535, i32 undef>
   ret <2 x i32> %r
 }
 define <2 x i32> @p10_vec_nonsplat_undef2(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @p10_vec_nonsplat_undef2(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult <2 x i32> [[X:%.*]], <i32 65536, i32 undef>
-; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T]], <2 x i32> [[Y:%.*]], <2 x i32> <i32 65535, i32 undef>
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 undef>
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 undef>, <2 x i32> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %t = icmp ult <2 x i32> %x, <i32 65536, i32 undef>
   %r = select <2 x i1> %t, <2 x i32> %y, <2 x i32> <i32 65535, i32 undef>
   ret <2 x i32> %r
 }
 
 ; Non-splat vectors
 
 define <2 x i32> @p11_vec_nonsplat(<2 x i32> %x, <2 x i32> %y) {
 ; CHECK-LABEL: @p11_vec_nonsplat(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult <2 x i32> [[X:%.*]], <i32 65536, i32 32768>
-; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T]], <2 x i32> [[Y:%.*]], <2 x i32> <i32 65535, i32 32767>
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt <2 x i32> [[X:%.*]], <i32 65535, i32 32767>
+; CHECK-NEXT:    [[R:%.*]] = select <2 x i1> [[T_INV]], <2 x i32> <i32 65535, i32 32767>, <2 x i32> [[Y:%.*]]
 ; CHECK-NEXT:    ret <2 x i32> [[R]]
 ;
   %t = icmp ult <2 x i32> %x, <i32 65536, i32 32768>
   %r = select <2 x i1> %t, <2 x i32> %y, <2 x i32> <i32 65535, i32 32767>
   ret <2 x i32> %r
 }
 
 ;------------------------------------------------------------------------------;

 
 ;------------------------------------------------------------------------------;
 ; Commutativity
 ;------------------------------------------------------------------------------;
 
 ; We don't care if the constant in select is true value or false value
 define i32 @p13_commutativity0(i32 %x, i32 %y) {
 ; CHECK-LABEL: @p13_commutativity0(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult i32 [[X:%.*]], 65536
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 65535, i32 [[Y:%.*]]
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt i32 [[X:%.*]], 65535
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 [[Y:%.*]], i32 65535
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp ult i32 %x, 65536
   %r = select i1 %t, i32 65535, i32 %y
   ret i32 %r
 }
 
 ; Which means, if both possibilities are constants, we must check both of them.
 define i32 @p14_commutativity1(i32 %x, i32 %y) {
 ; CHECK-LABEL: @p14_commutativity1(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult i32 [[X:%.*]], 65536
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 65535, i32 42
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt i32 [[X:%.*]], 65535
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 42, i32 65535
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp ult i32 %x, 65536
   %r = select i1 %t, i32 65535, i32 42
   ret i32 %r
 }
 define i32 @p15_commutativity2(i32 %x, i32 %y) {
 ; CHECK-LABEL: @p15_commutativity2(
-; CHECK-NEXT:    [[T:%.*]] = icmp ult i32 [[X:%.*]], 65536
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 42, i32 65535
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp ugt i32 [[X:%.*]], 65535
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 65535, i32 42
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp ult i32 %x, 65536
   %r = select i1 %t, i32 42, i32 65535
   ret i32 %r
 }
 
 ;------------------------------------------------------------------------------;

 ; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 2147483647, i32 [[Y:%.*]]
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp eq i32 %x, -2147483648
   %r = select i1 %t, i32 2147483647, i32 %y
   ret i32 %r
 }
 
-; We don't touch sign checks
-define i32 @n22_sign_check(i32 %x, i32 %y) {
-; CHECK-LABEL: @n22_sign_check(
-; CHECK-NEXT:    [[T:%.*]] = icmp slt i32 [[X:%.*]], 0
-; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 -1, i32 [[Y:%.*]]
+; There is nothing special about sign-bit-tests, we can fold them.
+define i32 @t22_sign_check(i32 %x, i32 %y) {
+; CHECK-LABEL: @t22_sign_check(
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp sgt i32 [[X:%.*]], -1
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 [[Y:%.*]], i32 -1
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %t = icmp slt i32 %x, 0
   %r = select i1 %t, i32 -1, i32 %y
   ret i32 %r
 }
+define i32 @t22_sign_check2(i32 %x, i32 %y) {
+; CHECK-LABEL: @t22_sign_check2(
+; CHECK-NEXT:    [[T_INV:%.*]] = icmp slt i32 [[X:%.*]], 0
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[T_INV]], i32 [[Y:%.*]], i32 0
+; CHECK-NEXT:    ret i32 [[R]]
+;
+  %t = icmp sgt i32 %x, -1
+  %r = select i1 %t, i32 0, i32 %y
+  ret i32 %r
+}
 
 ; If the types don't match we currently don't do anything.
 define i32 @n23_type_mismatch(i64 %x, i32 %y) {
 ; CHECK-LABEL: @n23_type_mismatch(
 ; CHECK-NEXT:    [[T:%.*]] = icmp ult i64 [[X:%.*]], 65536
 ; CHECK-NEXT:    [[R:%.*]] = select i1 [[T]], i32 [[Y:%.*]], i32 65535
 ; CHECK-NEXT:    ret i32 [[R]]
 ;

 ;
   %t = icmp ult i32 %x, 65536
   %r = select i1 %t, i32 65536, i32 65535
   ret i32 %r
 }
 
 
 
-; CHECK: !0 = !{!"branch_weights", i32 2000, i32 1}
+; CHECK: !0 = !{!"branch_weights", i32 1, i32 2000}

llvm/test/Transforms/InstCombine/unrecognized_three-way-comparison.ll

 
 exit:
   ret i32 42
 }
 
 define i32 @compare_against_zero(i32 %x) {
 ; CHECK-LABEL: @compare_against_zero(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[TMP0:%.*]] = icmp sgt i32 [[X:%.*]], 0
-; CHECK-NEXT:    br i1 [[TMP0]], label [[CALLFOO:%.*]], label [[EXIT:%.*]]
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp eq i32 [[X:%.*]], 0
+; CHECK-NEXT:    [[CMP2_INV:%.*]] = icmp sgt i32 [[X]], -1
+; CHECK-NEXT:    [[SELECT1:%.*]] = select i1 [[CMP2_INV]], i32 1, i32 -1
+; CHECK-NEXT:    [[SELECT2:%.*]] = select i1 [[CMP1]], i32 0, i32 [[SELECT1]]
+; CHECK-NEXT:    [[COND:%.*]] = icmp sgt i32 [[SELECT2]], 0
+; CHECK-NEXT:    br i1 [[COND]], label [[CALLFOO:%.*]], label [[EXIT:%.*]]
 ; CHECK:       callfoo:
-; CHECK-NEXT:    call void @foo(i32 1)
+; CHECK-NEXT:    call void @foo(i32 [[SELECT2]])
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret i32 42
 ;
 
 entry:
   %cmp1 = icmp eq i32 %x, 0
   %cmp2 = icmp slt i32 %x, 0

 callfoo:
   call void @foo(i32 %select2)
   br label %exit
 
 exit:
   ret i32 42
 }
 
 define i32 @compare_against_two(i32 %x) {
 ; CHECK-LABEL: @compare_against_two(
 ; CHECK-NEXT:  entry:
-; CHECK-NEXT:    [[TMP0:%.*]] = icmp sgt i32 [[X:%.*]], 2
-; CHECK-NEXT:    br i1 [[TMP0]], label [[CALLFOO:%.*]], label [[EXIT:%.*]]
+; CHECK-NEXT:    [[CMP1:%.*]] = icmp eq i32 [[X:%.*]], 2
+; CHECK-NEXT:    [[CMP2_INV:%.*]] = icmp sgt i32 [[X]], 1
+; CHECK-NEXT:    [[SELECT1:%.*]] = select i1 [[CMP2_INV]], i32 1, i32 -1
+; CHECK-NEXT:    [[SELECT2:%.*]] = select i1 [[CMP1]], i32 0, i32 [[SELECT1]]
+; CHECK-NEXT:    [[COND:%.*]] = icmp sgt i32 [[SELECT2]], 0
+; CHECK-NEXT:    br i1 [[COND]], label [[CALLFOO:%.*]], label [[EXIT:%.*]]
 ; CHECK:       callfoo:
-; CHECK-NEXT:    call void @foo(i32 1)
+; CHECK-NEXT:    call void @foo(i32 [[SELECT2]])
 ; CHECK-NEXT:    br label [[EXIT]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    ret i32 42
 ;
 
 entry:
   %cmp1 = icmp eq i32 %x, 2
   %cmp2 = icmp slt i32 %x, 2
   %select1 = select i1 %cmp2, i32 -1, i32 1
   %select2 = select i1 %cmp1, i32 0, i32 %select1
   %cond = icmp sgt i32 %select2, 0
   br i1 %cond, label %callfoo, label %exit

llvm/test/Transforms/InstCombine/xor-of-icmps-with-extra-uses.ll

 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
 ; RUN: opt < %s -instcombine -S | FileCheck %s
 
 ; These xor-of-icmps could be replaced with and-of-icmps, but %cond0 has extra
 ; uses, so we don't consider it, even though some cases are freely invertible.
 
 ; %cond0 is extra-used in select, which is freely invertible.
 define i1 @v0_select_of_consts(i32 %X, i32* %selected) {
 ; CHECK-LABEL: @v0_select_of_consts(
-; CHECK-NEXT:    [[COND0:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[COND0]], i32 -32768, i32 32767
+; CHECK-NEXT:    [[COND0_INV:%.*]] = icmp sgt i32 [[X:%.*]], 32767
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[COND0_INV]], i32 32767, i32 -32768
 ; CHECK-NEXT:    store i32 [[SELECT]], i32* [[SELECTED:%.*]], align 4
 ; CHECK-NEXT:    [[X_OFF:%.*]] = add i32 [[X]], 32767
 ; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[X_OFF]], 65535
 ; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %cond0 = icmp sgt i32 %X, 32767
   %cond1 = icmp sgt i32 %X, -32768
   %select = select i1 %cond0, i32 32767, i32 -32768
;
   %cond1 = icmp sgt i32 %X, -32768
   %select = select i1 %cond0, i32 %Y, i32 -32768
   store i32 %select, i32* %selected
   %res = xor i1 %cond0, %cond1
   ret i1 %res
 }
 define i1 @v2_select_of_const_and_var(i32 %X, i32 %Y, i32* %selected) {
 ; CHECK-LABEL: @v2_select_of_const_and_var(
-; CHECK-NEXT:    [[COND0:%.*]] = icmp slt i32 [[X:%.*]], 32768
-; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[COND0]], i32 [[Y:%.*]], i32 32767
+; CHECK-NEXT:    [[COND0_INV:%.*]] = icmp sgt i32 [[X:%.*]], 32767
+; CHECK-NEXT:    [[SELECT:%.*]] = select i1 [[COND0_INV]], i32 32767, i32 [[Y:%.*]]
 ; CHECK-NEXT:    store i32 [[SELECT]], i32* [[SELECTED:%.*]], align 4
 ; CHECK-NEXT:    [[X_OFF:%.*]] = add i32 [[X]], 32767
 ; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[X_OFF]], 65535
 ; CHECK-NEXT:    ret i1 [[TMP1]]
 ;
   %cond0 = icmp sgt i32 %X, 32767
   %cond1 = icmp sgt i32 %X, -32768
   %select = select i1 %cond0, i32 32767, i32 %Y