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[Test] Add test showing that SCEV fails to evaluate symbolic max for …
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…'and' conditions
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@xortator
xortator committed Nov 25, 2022
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230 changes: 230 additions & 0 deletions llvm/test/Analysis/ScalarEvolution/symbolic_max_exit_count.ll
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; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
; RUN: opt -disable-output "-passes=print<scalar-evolution>" < %s 2>&1 | FileCheck %s

declare i1 @cond()

define i32 @test_simple_case(i32 %start, i32 %len) {
; CHECK-LABEL: 'test_simple_case'
; CHECK-NEXT: Classifying expressions for: @test_simple_case
; CHECK-NEXT: %iv = phi i32 [ %start, %entry ], [ %iv.next, %backedge ]
; CHECK-NEXT: --> {%start,+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.minus.1 = add i32 %iv, -1
; CHECK-NEXT: --> {(-1 + %start),+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = add i32 %iv, -1
; CHECK-NEXT: --> {(-1 + %start),+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %loop_cond = call i1 @cond()
; CHECK-NEXT: --> %loop_cond U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_simple_case
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: %start
; CHECK-NEXT: exit count for range_check_block: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for backedge: ***COULDNOTCOMPUTE***
; CHECK-NEXT: Loop %loop: constant max backedge-taken count is -1
; CHECK-NEXT: Loop %loop: symbolic max backedge-taken count is %start
; CHECK-NEXT: symbolic max exit count for loop: %start
; CHECK-NEXT: symbolic max exit count for range_check_block: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for backedge: ***COULDNOTCOMPUTE***
; CHECK-NEXT: Loop %loop: Unpredictable predicated backedge-taken count.
;
entry:
br label %loop

loop:
%iv = phi i32 [%start, %entry], [%iv.next, %backedge]
%zero_check = icmp ne i32 %iv, 0
br i1 %zero_check, label %range_check_block, label %failed_1

range_check_block:
%iv.minus.1 = add i32 %iv, -1
%range_check = icmp ult i32 %iv.minus.1, %len
br i1 %range_check, label %backedge, label %failed_2

backedge:
%iv.next = add i32 %iv, -1
%loop_cond = call i1 @cond()
br i1 %loop_cond, label %done, label %loop

done:
ret i32 %iv

failed_1:
ret i32 -1

failed_2:
ret i32 -2
}

; TODO: Symbolic max can be %start
define i32 @test_litter_conditions(i32 %start, i32 %len) {
; CHECK-LABEL: 'test_litter_conditions'
; CHECK-NEXT: Classifying expressions for: @test_litter_conditions
; CHECK-NEXT: %iv = phi i32 [ %start, %entry ], [ %iv.next, %backedge ]
; CHECK-NEXT: --> {%start,+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %fake_1 = call i1 @cond()
; CHECK-NEXT: --> %fake_1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %and_1 = and i1 %zero_check, %fake_1
; CHECK-NEXT: --> (%zero_check umin %fake_1) U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.minus.1 = add i32 %iv, -1
; CHECK-NEXT: --> {(-1 + %start),+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %fake_2 = call i1 @cond()
; CHECK-NEXT: --> %fake_2 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %and_2 = and i1 %range_check, %fake_2
; CHECK-NEXT: --> (%range_check umin %fake_2) U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i32 %iv, -1
; CHECK-NEXT: --> {(-1 + %start),+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %loop_cond = call i1 @cond()
; CHECK-NEXT: --> %loop_cond U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_litter_conditions
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for range_check_block: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for backedge: ***COULDNOTCOMPUTE***
; CHECK-NEXT: Loop %loop: constant max backedge-taken count is -1
; CHECK-NEXT: Loop %loop: Unpredictable symbolic max backedge-taken count.
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for range_check_block: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for backedge: ***COULDNOTCOMPUTE***
; CHECK-NEXT: Loop %loop: Unpredictable predicated backedge-taken count.
;
entry:
br label %loop

loop:
%iv = phi i32 [%start, %entry], [%iv.next, %backedge]
%zero_check = icmp ne i32 %iv, 0
%fake_1 = call i1 @cond()
%and_1 = and i1 %zero_check, %fake_1
br i1 %and_1, label %range_check_block, label %failed_1

range_check_block:
%iv.minus.1 = add i32 %iv, -1
%range_check = icmp ult i32 %iv.minus.1, %len
%fake_2 = call i1 @cond()
%and_2 = and i1 %range_check, %fake_2
br i1 %and_2, label %backedge, label %failed_2

backedge:
%iv.next = add i32 %iv, -1
%loop_cond = call i1 @cond()
br i1 %loop_cond, label %done, label %loop

done:
ret i32 %iv

failed_1:
ret i32 -1

failed_2:
ret i32 -2
}

; TODO: Symbolic max can be %start
define i32 @test_litter_conditions_bad_context(i32 %start, i32 %len) {
; CHECK-LABEL: 'test_litter_conditions_bad_context'
; CHECK-NEXT: Classifying expressions for: @test_litter_conditions_bad_context
; CHECK-NEXT: %iv = phi i32 [ %start, %entry ], [ %iv.next, %backedge ]
; CHECK-NEXT: --> {%start,+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %fake_1 = call i1 @cond()
; CHECK-NEXT: --> %fake_1 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %and_1 = and i1 %zero_check, %fake_1
; CHECK-NEXT: --> (%zero_check umin %fake_1) U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.minus.1 = add i32 %iv, -1
; CHECK-NEXT: --> {(-1 + %start),+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %fake_2 = call i1 @cond()
; CHECK-NEXT: --> %fake_2 U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %and_2 = and i1 %range_check, %fake_2
; CHECK-NEXT: --> (%range_check umin %fake_2) U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i32 %iv, -1
; CHECK-NEXT: --> {(-1 + %start),+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %loop_cond = call i1 @cond()
; CHECK-NEXT: --> %loop_cond U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_litter_conditions_bad_context
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for range_check_block: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for backedge: ***COULDNOTCOMPUTE***
; CHECK-NEXT: Loop %loop: constant max backedge-taken count is -1
; CHECK-NEXT: Loop %loop: Unpredictable symbolic max backedge-taken count.
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for range_check_block: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for backedge: ***COULDNOTCOMPUTE***
; CHECK-NEXT: Loop %loop: Unpredictable predicated backedge-taken count.
;
entry:
br label %loop

loop:
%iv = phi i32 [%start, %entry], [%iv.next, %backedge]
%zero_check = icmp ne i32 %iv, 0
%fake_1 = call i1 @cond()
%and_1 = and i1 %zero_check, %fake_1
%iv.minus.1 = add i32 %iv, -1
%range_check = icmp ult i32 %iv.minus.1, %len
%fake_2 = call i1 @cond()
%and_2 = and i1 %range_check, %fake_2
br i1 %and_1, label %range_check_block, label %failed_1

range_check_block:
br i1 %and_2, label %backedge, label %failed_2

backedge:
%iv.next = add i32 %iv, -1
%loop_cond = call i1 @cond()
br i1 %loop_cond, label %done, label %loop

done:
ret i32 %iv

failed_1:
ret i32 -1

failed_2:
ret i32 -2
}

; TODO: Symbolic max can be %start
define i32 @test_and_conditions(i32 %start, i32 %len) {
; CHECK-LABEL: 'test_and_conditions'
; CHECK-NEXT: Classifying expressions for: @test_and_conditions
; CHECK-NEXT: %iv = phi i32 [ %start, %entry ], [ %iv.next, %backedge ]
; CHECK-NEXT: --> {%start,+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.minus.1 = add i32 %iv, -1
; CHECK-NEXT: --> {(-1 + %start),+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %both_checks = and i1 %zero_check, %range_check
; CHECK-NEXT: --> (%range_check umin %zero_check) U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: %iv.next = add i32 %iv, -1
; CHECK-NEXT: --> {(-1 + %start),+,-1}<%loop> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %loop_cond = call i1 @cond()
; CHECK-NEXT: --> %loop_cond U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %loop: Variant }
; CHECK-NEXT: Determining loop execution counts for: @test_and_conditions
; CHECK-NEXT: Loop %loop: <multiple exits> Unpredictable backedge-taken count.
; CHECK-NEXT: exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: exit count for backedge: ***COULDNOTCOMPUTE***
; CHECK-NEXT: Loop %loop: constant max backedge-taken count is -1
; CHECK-NEXT: Loop %loop: Unpredictable symbolic max backedge-taken count.
; CHECK-NEXT: symbolic max exit count for loop: ***COULDNOTCOMPUTE***
; CHECK-NEXT: symbolic max exit count for backedge: ***COULDNOTCOMPUTE***
; CHECK-NEXT: Loop %loop: Unpredictable predicated backedge-taken count.
;
entry:
br label %loop

loop:
%iv = phi i32 [%start, %entry], [%iv.next, %backedge]
%zero_check = icmp ne i32 %iv, 0
%iv.minus.1 = add i32 %iv, -1
%range_check = icmp ult i32 %iv.minus.1, %len
%both_checks = and i1 %zero_check, %range_check
br i1 %both_checks, label %backedge, label %failed

backedge:
%iv.next = add i32 %iv, -1
%loop_cond = call i1 @cond()
br i1 %loop_cond, label %done, label %loop

done:
ret i32 %iv

failed:
ret i32 -3
}

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