LICM: teach hoistMinMax about samesign

Follow up on 4a0d53a (PatternMatch: migrate to CmpPredicate) to get rid
of one of the FIXMEs it introduced by replacing a predicate comparison
with CmpPredicate::getMatching.

Author: artagnon

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -2453,16 +2453,16 @@ static bool hoistMinMax(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo,
   if (!MatchICmpAgainstInvariant(Cond1, P1, LHS1, RHS1) ||
       !MatchICmpAgainstInvariant(Cond2, P2, LHS2, RHS2))
     return false;
-  // FIXME: Use CmpPredicate::getMatching here.
-  if (P1 != static_cast<CmpInst::Predicate>(P2) || LHS1 != LHS2)
+  auto MatchingPred = CmpPredicate::getMatching(P1, P2);
+  if (!MatchingPred || LHS1 != LHS2)
     return false;
 
   // Everything is fine, we can do the transform.
   bool UseMin = ICmpInst::isLT(P1) || ICmpInst::isLE(P1);
   assert(
       (UseMin || ICmpInst::isGT(P1) || ICmpInst::isGE(P1)) &&
       "Relational predicate is either less (or equal) or greater (or equal)!");
-  Intrinsic::ID id = ICmpInst::isSigned(P1)
+  Intrinsic::ID id = ICmpInst::isSigned(*MatchingPred)
                          ? (UseMin ? Intrinsic::smin : Intrinsic::smax)
                          : (UseMin ? Intrinsic::umin : Intrinsic::umax);
   auto *Preheader = L.getLoopPreheader();
@@ -2479,7 +2479,7 @@ static bool hoistMinMax(Instruction &I, Loop &L, ICFLoopSafetyInfo &SafetyInfo,
                                    (ICmpInst::isSigned(P1) ? "s" : "u") +
                                    (UseMin ? "min" : "max"));
   Builder.SetInsertPoint(&I);
-  ICmpInst::Predicate P = P1;
+  ICmpInst::Predicate P = *MatchingPred;
   if (Inverse)
     P = ICmpInst::getInversePredicate(P);
   Value *NewCond = Builder.CreateICmp(P, LHS1, NewRHS);

llvm/test/Transforms/LICM/min_max.ll

@@ -245,12 +245,11 @@ exit:
 define i32 @test_sgt_samesign(i32 %start, i32 %inv_1, i32 %inv_2) {
 ; CHECK-LABEL: @test_sgt_samesign(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INVARIANT_UMAX:%.*]] = call i32 @llvm.smax.i32(i32 [[INV_1:%.*]], i32 [[INV_2:%.*]])
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[CMP_1:%.*]] = icmp samesign ugt i32 [[IV]], [[INV_1:%.*]]
-; CHECK-NEXT:    [[CMP_2:%.*]] = icmp sgt i32 [[IV]], [[INV_2:%.*]]
-; CHECK-NEXT:    [[LOOP_COND:%.*]] = and i1 [[CMP_1]], [[CMP_2]]
+; CHECK-NEXT:    [[LOOP_COND:%.*]] = icmp sgt i32 [[IV]], [[INVARIANT_UMAX]]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1
 ; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
 ; CHECK:       exit:
@@ -305,14 +304,13 @@ exit:
 define i32 @test_sge_samesign(i32 %start, i32 %inv_1, i32 %inv_2) {
 ; CHECK-LABEL: @test_sge_samesign(
 ; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[INV_1:%.*]] = call i32 @llvm.smax.i32(i32 [[INV_3:%.*]], i32 [[INV_2:%.*]])
 ; CHECK-NEXT:    br label [[LOOP:%.*]]
 ; CHECK:       loop:
 ; CHECK-NEXT:    [[IV:%.*]] = phi i32 [ [[START:%.*]], [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
-; CHECK-NEXT:    [[CMP_1:%.*]] = icmp sge i32 [[IV]], [[INV_1:%.*]]
-; CHECK-NEXT:    [[CMP_2:%.*]] = icmp samesign uge i32 [[IV]], [[INV_2:%.*]]
-; CHECK-NEXT:    [[LOOP_COND:%.*]] = and i1 [[CMP_1]], [[CMP_2]]
+; CHECK-NEXT:    [[CMP_1:%.*]] = icmp sge i32 [[IV]], [[INV_1]]
 ; CHECK-NEXT:    [[IV_NEXT]] = add i32 [[IV]], 1
-; CHECK-NEXT:    br i1 [[LOOP_COND]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK-NEXT:    br i1 [[CMP_1]], label [[LOOP]], label [[EXIT:%.*]]
 ; CHECK:       exit:
 ; CHECK-NEXT:    [[IV_LCSSA:%.*]] = phi i32 [ [[IV]], [[LOOP]] ]
 ; CHECK-NEXT:    ret i32 [[IV_LCSSA]]