1; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py 2; RUN: opt < %s -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s 3 4target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" 5 6@A = weak global [1000 x i32] zeroinitializer, align 32 7 8; The resulting predicate is i16 {0,+,1} <nssw>, meanining 9; that the resulting backedge expression will be valid for: 10; (1 + (-1 smax %M)) <= MAX_INT16 11; 12; At the limit condition for M (MAX_INT16 - 1) we have in the 13; last iteration: 14; i0 <- MAX_INT16 15; i0.ext <- MAX_INT16 16; 17; and therefore no wrapping happend for i0 or i0.ext 18; throughout the execution of the loop. The resulting predicated 19; backedge taken count is correct. 20 21define void @test1(i32 %N, i32 %M) { 22; CHECK-LABEL: 'test1' 23; CHECK-NEXT: Classifying expressions for: @test1 24; CHECK-NEXT: %tmp = getelementptr [1000 x i32], ptr @A, i32 0, i16 %i.0 25; CHECK-NEXT: --> ((4 * (sext i16 {0,+,1}<%bb3> to i64))<nsw> + @A) U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: <<Unknown>> LoopDispositions: { %bb3: Computable } 26; CHECK-NEXT: %tmp2 = add i16 %i.0, 1 27; CHECK-NEXT: --> {1,+,1}<%bb3> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb3: Computable } 28; CHECK-NEXT: %i.0 = phi i16 [ 0, %entry ], [ %tmp2, %bb ] 29; CHECK-NEXT: --> {0,+,1}<%bb3> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb3: Computable } 30; CHECK-NEXT: %i.0.ext = sext i16 %i.0 to i32 31; CHECK-NEXT: --> (sext i16 {0,+,1}<%bb3> to i32) U: [-32768,32768) S: [-32768,32768) Exits: <<Unknown>> LoopDispositions: { %bb3: Computable } 32; CHECK-NEXT: Determining loop execution counts for: @test1 33; CHECK-NEXT: Loop %bb3: Unpredictable backedge-taken count. 34; CHECK-NEXT: Loop %bb3: Unpredictable constant max backedge-taken count. 35; CHECK-NEXT: Loop %bb3: Unpredictable symbolic max backedge-taken count. 36; CHECK-NEXT: Loop %bb3: Predicated backedge-taken count is (1 + (-1 smax %M)) 37; CHECK-NEXT: Predicates: 38; CHECK-NEXT: {0,+,1}<%bb3> Added Flags: <nssw> 39; 40entry: 41 br label %bb3 42 43bb: ; preds = %bb3 44 %tmp = getelementptr [1000 x i32], ptr @A, i32 0, i16 %i.0 ; <ptr> [#uses=1] 45 store i32 123, ptr %tmp 46 %tmp2 = add i16 %i.0, 1 ; <i32> [#uses=1] 47 br label %bb3 48 49bb3: ; preds = %bb, %entry 50 %i.0 = phi i16 [ 0, %entry ], [ %tmp2, %bb ] ; <i32> [#uses=3] 51 %i.0.ext = sext i16 %i.0 to i32 52 %tmp3 = icmp sle i32 %i.0.ext, %M ; <i1> [#uses=1] 53 br i1 %tmp3, label %bb, label %bb5 54 55bb5: ; preds = %bb3 56 br label %return 57 58return: ; preds = %bb5 59 ret void 60} 61 62; The predicated backedge taken count is: 63; (2 + (zext i16 %Start to i32) + ((-2 + (-1 * (sext i16 %Start to i32))) 64; smax (-1 + (-1 * %M))) 65; ) 66 67; -1 + (-1 * %M) <= (-2 + (-1 * (sext i16 %Start to i32)) 68; The predicated backedge taken count is 0. 69; From the IR, this is correct since we will bail out at the 70; first iteration. 71 72 73; * -1 + (-1 * %M) > (-2 + (-1 * (sext i16 %Start to i32)) 74; or: %M < 1 + (sext i16 %Start to i32) 75; 76; The predicated backedge taken count is 1 + (zext i16 %Start to i32) - %M 77; 78; If %M >= MIN_INT + 1, this predicated backedge taken count would be correct (even 79; without predicates). However, for %M < MIN_INT this would be an infinite loop. 80; In these cases, the {%Start,+,-1} <nusw> predicate would be false, as the 81; final value of the expression {%Start,+,-1} expression (%M - 1) would not be 82; representable as an i16. 83 84; There is also a limit case here where the value of %M is MIN_INT. In this case 85; we still have an infinite loop, since icmp sge %x, MIN_INT will always return 86; true. 87 88define void @test2(i32 %N, i32 %M, i16 %Start) { 89; CHECK-LABEL: 'test2' 90; CHECK-NEXT: Classifying expressions for: @test2 91; CHECK-NEXT: %tmp = getelementptr [1000 x i32], ptr @A, i32 0, i16 %i.0 92; CHECK-NEXT: --> ((4 * (sext i16 {%Start,+,-1}<%bb3> to i64))<nsw> + @A) U: [0,-3) S: [-9223372036854775808,9223372036854775805) Exits: <<Unknown>> LoopDispositions: { %bb3: Computable } 93; CHECK-NEXT: %tmp2 = sub i16 %i.0, 1 94; CHECK-NEXT: --> {(-1 + %Start),+,-1}<%bb3> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb3: Computable } 95; CHECK-NEXT: %i.0 = phi i16 [ %Start, %entry ], [ %tmp2, %bb ] 96; CHECK-NEXT: --> {%Start,+,-1}<%bb3> U: full-set S: full-set Exits: <<Unknown>> LoopDispositions: { %bb3: Computable } 97; CHECK-NEXT: %i.0.ext = sext i16 %i.0 to i32 98; CHECK-NEXT: --> (sext i16 {%Start,+,-1}<%bb3> to i32) U: [-32768,32768) S: [-32768,32768) Exits: <<Unknown>> LoopDispositions: { %bb3: Computable } 99; CHECK-NEXT: Determining loop execution counts for: @test2 100; CHECK-NEXT: Loop %bb3: Unpredictable backedge-taken count. 101; CHECK-NEXT: Loop %bb3: Unpredictable constant max backedge-taken count. 102; CHECK-NEXT: Loop %bb3: Unpredictable symbolic max backedge-taken count. 103; CHECK-NEXT: Loop %bb3: Predicated backedge-taken count is (1 + (sext i16 %Start to i32) + (-1 * ((1 + (sext i16 %Start to i32))<nsw> smin %M))) 104; CHECK-NEXT: Predicates: 105; CHECK-NEXT: {%Start,+,-1}<%bb3> Added Flags: <nssw> 106; 107entry: 108 br label %bb3 109 110bb: ; preds = %bb3 111 %tmp = getelementptr [1000 x i32], ptr @A, i32 0, i16 %i.0 ; <ptr> [#uses=1] 112 store i32 123, ptr %tmp 113 %tmp2 = sub i16 %i.0, 1 ; <i32> [#uses=1] 114 br label %bb3 115 116bb3: ; preds = %bb, %entry 117 %i.0 = phi i16 [ %Start, %entry ], [ %tmp2, %bb ] ; <i32> [#uses=3] 118 %i.0.ext = sext i16 %i.0 to i32 119 %tmp3 = icmp sge i32 %i.0.ext, %M ; <i1> [#uses=1] 120 br i1 %tmp3, label %bb, label %bb5 121 122bb5: ; preds = %bb3 123 br label %return 124 125return: ; preds = %bb5 126 ret void 127} 128 129