VT: teach isImpliedCondMatchingOperands about samesign (#122474)

artagnon · web-flow · commit f38c40bff399 · 2025-01-11T09:08:57.000Z
Move isImplied{True,False}ByMatchingCmp from CmpInst to ICmpInst, so
that it can operate on CmpPredicate instead of CmpInst::Predicate, and
teach it about samesign. There are two callers of this function, and we
choose to migrate the one in ValueTracking, namely
isImpliedCondMatchingOperands to CmpPredicate, hence teaching it about
samesign, with visible test impact.
diff --git a/llvm/include/llvm/IR/InstrTypes.h b/llvm/include/llvm/IR/InstrTypes.h
@@ -967,14 +967,6 @@ class CmpInst : public Instruction {
   /// Determine if the predicate is false when comparing a value with itself.
   static bool isFalseWhenEqual(Predicate predicate);
 
-  /// Determine if Pred1 implies Pred2 is true when two compares have matching
-  /// operands.
-  static bool isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2);
-
-  /// Determine if Pred1 implies Pred2 is false when two compares have matching
-  /// operands.
-  static bool isImpliedFalseByMatchingCmp(Predicate Pred1, Predicate Pred2);
-
   /// Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Instruction *I) {
     return I->getOpcode() == Instruction::ICmp ||
diff --git a/llvm/include/llvm/IR/Instructions.h b/llvm/include/llvm/IR/Instructions.h
@@ -1266,6 +1266,16 @@ class ICmpInst: public CmpInst {
     return getFlippedSignednessPredicate(getPredicate());
   }
 
+  /// Determine if Pred1 implies Pred2 is true when two compares have matching
+  /// operands.
+  static bool isImpliedTrueByMatchingCmp(CmpPredicate Pred1,
+                                         CmpPredicate Pred2);
+
+  /// Determine if Pred1 implies Pred2 is false when two compares have matching
+  /// operands.
+  static bool isImpliedFalseByMatchingCmp(CmpPredicate Pred1,
+                                          CmpPredicate Pred2);
+
   void setSameSign(bool B = true) {
     SubclassOptionalData = (SubclassOptionalData & ~SameSign) | (B * SameSign);
   }
diff --git a/llvm/include/llvm/SandboxIR/Instruction.h b/llvm/include/llvm/SandboxIR/Instruction.h
@@ -2511,13 +2511,6 @@ class CmpInst : public SingleLLVMInstructionImpl<llvm::CmpInst> {
   WRAP_STATIC_PREDICATE(isOrdered);
   WRAP_STATIC_PREDICATE(isUnordered);
 
-  static bool isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2) {
-    return llvm::CmpInst::isImpliedTrueByMatchingCmp(Pred1, Pred2);
-  }
-  static bool isImpliedFalseByMatchingCmp(Predicate Pred1, Predicate Pred2) {
-    return llvm::CmpInst::isImpliedFalseByMatchingCmp(Pred1, Pred2);
-  }
-
   /// Method for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Value *From) {
     return From->getSubclassID() == ClassID::ICmp ||
@@ -2554,6 +2547,15 @@ class ICmpInst : public CmpInst {
   WRAP_STATIC_PREDICATE(isGE);
   WRAP_STATIC_PREDICATE(isLE);
 
+  static bool isImpliedTrueByMatchingCmp(CmpPredicate Pred1,
+                                         CmpPredicate Pred2) {
+    return llvm::ICmpInst::isImpliedTrueByMatchingCmp(Pred1, Pred2);
+  }
+  static bool isImpliedFalseByMatchingCmp(CmpPredicate Pred1,
+                                          CmpPredicate Pred2) {
+    return llvm::ICmpInst::isImpliedFalseByMatchingCmp(Pred1, Pred2);
+  }
+
   static auto predicates() { return llvm::ICmpInst::predicates(); }
   static bool compare(const APInt &LHS, const APInt &RHS,
                       ICmpInst::Predicate Pred) {
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
@@ -9387,12 +9387,11 @@ isImpliedCondOperands(CmpInst::Predicate Pred, const Value *ALHS,
 /// Return true if "icmp1 LPred X, Y" implies "icmp2 RPred X, Y" is true.
 /// Return false if "icmp1 LPred X, Y" implies "icmp2 RPred X, Y" is false.
 /// Otherwise, return std::nullopt if we can't infer anything.
-static std::optional<bool>
-isImpliedCondMatchingOperands(CmpInst::Predicate LPred,
-                              CmpInst::Predicate RPred) {
-  if (CmpInst::isImpliedTrueByMatchingCmp(LPred, RPred))
+static std::optional<bool> isImpliedCondMatchingOperands(CmpPredicate LPred,
+                                                         CmpPredicate RPred) {
+  if (ICmpInst::isImpliedTrueByMatchingCmp(LPred, RPred))
     return true;
-  if (CmpInst::isImpliedFalseByMatchingCmp(LPred, RPred))
+  if (ICmpInst::isImpliedFalseByMatchingCmp(LPred, RPred))
     return false;
 
   return std::nullopt;
diff --git a/llvm/lib/IR/Instructions.cpp b/llvm/lib/IR/Instructions.cpp
@@ -3886,12 +3886,18 @@ bool CmpInst::isFalseWhenEqual(Predicate predicate) {
   }
 }
 
-bool CmpInst::isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2) {
+bool ICmpInst::isImpliedTrueByMatchingCmp(CmpPredicate Pred1,
+                                          CmpPredicate Pred2) {
   // If the predicates match, then we know the first condition implies the
   // second is true.
-  if (Pred1 == Pred2)
+  if (CmpPredicate::getMatching(Pred1, Pred2))
     return true;
 
+  if (Pred1.hasSameSign() && CmpInst::isSigned(Pred2))
+    Pred1 = ICmpInst::getFlippedSignednessPredicate(Pred1);
+  else if (Pred2.hasSameSign() && CmpInst::isSigned(Pred1))
+    Pred2 = ICmpInst::getFlippedSignednessPredicate(Pred2);
+
   switch (Pred1) {
   default:
     break;
@@ -3911,7 +3917,8 @@ bool CmpInst::isImpliedTrueByMatchingCmp(Predicate Pred1, Predicate Pred2) {
   return false;
 }
 
-bool CmpInst::isImpliedFalseByMatchingCmp(Predicate Pred1, Predicate Pred2) {
+bool ICmpInst::isImpliedFalseByMatchingCmp(CmpPredicate Pred1,
+                                           CmpPredicate Pred2) {
   return isImpliedTrueByMatchingCmp(Pred1, getInversePredicate(Pred2));
 }
 
diff --git a/llvm/lib/Transforms/Scalar/NewGVN.cpp b/llvm/lib/Transforms/Scalar/NewGVN.cpp
@@ -1964,15 +1964,15 @@ NewGVN::ExprResult NewGVN::performSymbolicCmpEvaluation(Instruction *I) const {
         if (PBranch->TrueEdge) {
           // If we know the previous predicate is true and we are in the true
           // edge then we may be implied true or false.
-          if (CmpInst::isImpliedTrueByMatchingCmp(BranchPredicate,
-                                                  OurPredicate)) {
+          if (ICmpInst::isImpliedTrueByMatchingCmp(BranchPredicate,
+                                                   OurPredicate)) {
             return ExprResult::some(
                 createConstantExpression(ConstantInt::getTrue(CI->getType())),
                 PI);
           }
 
-          if (CmpInst::isImpliedFalseByMatchingCmp(BranchPredicate,
-                                                   OurPredicate)) {
+          if (ICmpInst::isImpliedFalseByMatchingCmp(BranchPredicate,
+                                                    OurPredicate)) {
             return ExprResult::some(
                 createConstantExpression(ConstantInt::getFalse(CI->getType())),
                 PI);
diff --git a/llvm/test/Analysis/ValueTracking/implied-condition-samesign.ll b/llvm/test/Analysis/ValueTracking/implied-condition-samesign.ll
@@ -118,8 +118,7 @@ define i1 @sgt_implies_ge_via_assume(i32 %i, i32 %j) {
 ; CHECK-SAME: i32 [[I:%.*]], i32 [[J:%.*]]) {
 ; CHECK-NEXT:    [[I_SGT_J:%.*]] = icmp sgt i32 [[I]], [[J]]
 ; CHECK-NEXT:    call void @llvm.assume(i1 [[I_SGT_J]])
-; CHECK-NEXT:    [[I_GE_J:%.*]] = icmp samesign uge i32 [[I]], [[J]]
-; CHECK-NEXT:    ret i1 [[I_GE_J]]
+; CHECK-NEXT:    ret i1 true
 ;
   %i.sgt.j = icmp sgt i32 %i, %j
   call void @llvm.assume(i1 %i.sgt.j)
@@ -134,9 +133,7 @@ define i32 @gt_implies_sge_dominating(i32 %a, i32 %len) {
 ; CHECK-NEXT:    [[A_GT_LEN:%.*]] = icmp samesign ugt i32 [[A]], [[LEN]]
 ; CHECK-NEXT:    br i1 [[A_GT_LEN]], label %[[TAKEN:.*]], label %[[END:.*]]
 ; CHECK:       [[TAKEN]]:
-; CHECK-NEXT:    [[A_SGE_LEN:%.*]] = icmp sge i32 [[A]], [[LEN]]
-; CHECK-NEXT:    [[RES:%.*]] = select i1 [[A_SGE_LEN]], i32 30, i32 0
-; CHECK-NEXT:    ret i32 [[RES]]
+; CHECK-NEXT:    ret i32 30
 ; CHECK:       [[END]]:
 ; CHECK-NEXT:    ret i32 -1
 ;
