[SCEV] Preserve divisor info when adding guard info for ICMP_NE via Sub.

Follow-up to #160500 to
preserve divisibiltiy info when creating the UMax.

Author: fhahn

llvm/lib/Analysis/ScalarEvolution.cpp

@@ -15836,8 +15836,9 @@ void ScalarEvolution::LoopGuards::collectFromBlock(
           }
           auto AddSubRewrite = [&](const SCEV *A, const SCEV *B) {
             const SCEV *Sub = SE.getMinusSCEV(A, B);
-            AddRewrite(Sub, Sub,
-                       SE.getUMaxExpr(Sub, SE.getOne(From->getType())));
+            const SCEV *OneAlignedUp = GetNextSCEVDividesByDivisor(
+                SE.getOne(From->getType()), SE.getConstantMultiple(Sub));
+            AddRewrite(Sub, Sub, SE.getUMaxExpr(Sub, OneAlignedUp));
           };
           AddSubRewrite(LHS, RHS);
           AddSubRewrite(RHS, LHS);

llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll

@@ -1431,7 +1431,7 @@ define void @ptr_induction_early_exit_eq_1_with_align_on_load(ptr %a, ptr %b, pt
 ; CHECK-NEXT:  Loop %loop: <multiple exits> Unpredictable backedge-taken count.
 ; CHECK-NEXT:    exit count for loop: ***COULDNOTCOMPUTE***
 ; CHECK-NEXT:    exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is i64 2305843009213693950
 ; CHECK-NEXT:  Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
 ; CHECK-NEXT:    symbolic max exit count for loop: ***COULDNOTCOMPUTE***
 ; CHECK-NEXT:    symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
@@ -1470,7 +1470,7 @@ define void @ptr_induction_early_exit_eq_1_with_align_on_arguments(ptr align 8 %
 ; CHECK-NEXT:  Loop %loop: <multiple exits> Unpredictable backedge-taken count.
 ; CHECK-NEXT:    exit count for loop: ***COULDNOTCOMPUTE***
 ; CHECK-NEXT:    exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8)
-; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is i64 2305843009213693950
 ; CHECK-NEXT:  Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8)
 ; CHECK-NEXT:    symbolic max exit count for loop: ***COULDNOTCOMPUTE***
 ; CHECK-NEXT:    symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a to i64)) + (ptrtoint ptr %b to i64)) /u 8)
@@ -1511,7 +1511,7 @@ define void @ptr_induction_early_exit_eq_1_align_assumption_1(ptr %a, ptr %b, pt
 ; CHECK-NEXT:  Loop %loop: <multiple exits> Unpredictable backedge-taken count.
 ; CHECK-NEXT:    exit count for loop: ***COULDNOTCOMPUTE***
 ; CHECK-NEXT:    exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is i64 2305843009213693950
 ; CHECK-NEXT:  Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
 ; CHECK-NEXT:    symbolic max exit count for loop: ***COULDNOTCOMPUTE***
 ; CHECK-NEXT:    symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
@@ -1556,7 +1556,7 @@ define void @ptr_induction_early_exit_eq_1_align_assumption_2(ptr %a, ptr %b, pt
 ; CHECK-NEXT:  Loop %loop: <multiple exits> Unpredictable backedge-taken count.
 ; CHECK-NEXT:    exit count for loop: ***COULDNOTCOMPUTE***
 ; CHECK-NEXT:    exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
-; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is i64 2305843009213693951
+; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is i64 2305843009213693950
 ; CHECK-NEXT:  Loop %loop: symbolic max backedge-taken count is ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)
 ; CHECK-NEXT:    symbolic max exit count for loop: ***COULDNOTCOMPUTE***
 ; CHECK-NEXT:    symbolic max exit count for loop.inc: ((-8 + (-1 * (ptrtoint ptr %a_ to i64)) + (ptrtoint ptr %b_ to i64)) /u 8)