[PATCH] D91942: [SCEV] Fix incorrect treatment of max taken count. PR48225

[Max Kazantsev via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rG48d7cc6ae23b: [SCEV] Fix incorrect treatment of max taken count. PR48225 (authored by mkazantsev).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D91942/new/

https://reviews.llvm.org/D91942

Files:
  llvm/lib/Analysis/ScalarEvolution.cpp
  llvm/test/Analysis/ScalarEvolution/pr48225.ll


Index: llvm/test/Analysis/ScalarEvolution/pr48225.ll
===================================================================
--- llvm/test/Analysis/ScalarEvolution/pr48225.ll
+++ llvm/test/Analysis/ScalarEvolution/pr48225.ll
@@ -4,7 +4,6 @@
 
 ; Tests demonstrate the bug reported as PR48225 by Congzhe Cao.
 
-; FIXME: This test demonstrates a bug in max backedge taken count computation.
 ; When %boolcond = false and %cond = 0:
 ; - %cond.false.on.first.iter is false on 1st iteration;
 ; - %cond.false.on.second.iter is false on 2nd iteration;
@@ -17,16 +16,16 @@
 ; CHECK-NEXT:    %conv = zext i1 %boolcond to i32
 ; CHECK-NEXT:    --> (zext i1 %boolcond to i32) U: [0,2) S: [0,2)
 ; CHECK-NEXT:    %iv = phi i32 [ 0, %entry ], [ %inc, %backedge ]
-; CHECK-NEXT:    --> {0,+,1}<nuw><nsw><%loop> U: [0,2) S: [0,2) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT:    --> {0,+,1}<nuw><nsw><%loop> U: [0,3) S: [0,3) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:    %or.cond = and i1 %cond.false.on.first.iter, %cond.false.on.second.iter
 ; CHECK-NEXT:    --> %or.cond U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
 ; CHECK-NEXT:    %inc = add nuw nsw i32 %iv, 1
-; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%loop> U: [1,3) S: [1,3) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%loop> U: [1,4) S: [1,4) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @test_and
 ; CHECK-NEXT:  Loop %loop: <multiple exits> Unpredictable backedge-taken count.
 ; CHECK-NEXT:    exit count for loop: 2
 ; CHECK-NEXT:    exit count for backedge: ***COULDNOTCOMPUTE***
-; CHECK-NEXT:  Loop %loop: max backedge-taken count is 1
+; CHECK-NEXT:  Loop %loop: max backedge-taken count is 2
 ; CHECK-NEXT:  Loop %loop: Unpredictable predicated backedge-taken count.
 ;
 entry:
@@ -52,7 +51,6 @@
   ret void
 }
 
-; FIXME: This test demonstrates a bug in max backedge taken count computation.
 ; When %boolcond = false and %cond = 0:
 ; - %cond.true.on.first.iter is true on 1st iteration;
 ; - %cond.true.on.second.iter is true on 2nd iteration;
@@ -65,16 +63,16 @@
 ; CHECK-NEXT:    %conv = zext i1 %boolcond to i32
 ; CHECK-NEXT:    --> (zext i1 %boolcond to i32) U: [0,2) S: [0,2)
 ; CHECK-NEXT:    %iv = phi i32 [ 0, %entry ], [ %inc, %backedge ]
-; CHECK-NEXT:    --> {0,+,1}<nuw><nsw><%loop> U: [0,2) S: [0,2) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT:    --> {0,+,1}<nuw><nsw><%loop> U: [0,3) S: [0,3) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:    %or.cond = or i1 %cond.true.on.first.iter, %cond.true.on.second.iter
 ; CHECK-NEXT:    --> %or.cond U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
 ; CHECK-NEXT:    %inc = add nuw nsw i32 %iv, 1
-; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%loop> U: [1,3) S: [1,3) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
+; CHECK-NEXT:    --> {1,+,1}<nuw><nsw><%loop> U: [1,4) S: [1,4) Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
 ; CHECK-NEXT:  Determining loop execution counts for: @test_or
 ; CHECK-NEXT:  Loop %loop: <multiple exits> Unpredictable backedge-taken count.
 ; CHECK-NEXT:    exit count for loop: 2
 ; CHECK-NEXT:    exit count for backedge: ***COULDNOTCOMPUTE***
-; CHECK-NEXT:  Loop %loop: max backedge-taken count is 1
+; CHECK-NEXT:  Loop %loop: max backedge-taken count is 2
 ; CHECK-NEXT:  Loop %loop: Unpredictable predicated backedge-taken count.
 ;
 entry:
Index: llvm/lib/Analysis/ScalarEvolution.cpp
===================================================================
--- llvm/lib/Analysis/ScalarEvolution.cpp
+++ llvm/lib/Analysis/ScalarEvolution.cpp
@@ -7611,8 +7611,6 @@
   } else {
     // Both conditions must be same at the same time for the loop to exit.
     // For now, be conservative.
-    if (EL0.MaxNotTaken == EL1.MaxNotTaken)
-      MaxBECount = EL0.MaxNotTaken;
     if (EL0.ExactNotTaken == EL1.ExactNotTaken)
       BECount = EL0.ExactNotTaken;
   }


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