| ; RUN: opt < %s -analyze -enable-new-pm=0 -scalar-evolution | FileCheck %s |
| ; RUN: opt < %s -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s |
| |
| target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" |
| |
| @A = weak global [1000 x i32] zeroinitializer, align 32 |
| |
| ; The resulting predicate is i16 {0,+,1} <nssw>, meanining |
| ; that the resulting backedge expression will be valid for: |
| ; (1 + (-1 smax %M)) <= MAX_INT16 |
| ; |
| ; At the limit condition for M (MAX_INT16 - 1) we have in the |
| ; last iteration: |
| ; i0 <- MAX_INT16 |
| ; i0.ext <- MAX_INT16 |
| ; |
| ; and therefore no wrapping happend for i0 or i0.ext |
| ; throughout the execution of the loop. The resulting predicated |
| ; backedge taken count is correct. |
| |
| ; CHECK: Classifying expressions for: @test1 |
| ; CHECK: %i.0.ext = sext i16 %i.0 to i32 |
| ; CHECK-NEXT: --> (sext i16 {0,+,1}<%bb3> to i32) |
| ; CHECK: Loop %bb3: Unpredictable backedge-taken count. |
| ; CHECK-NEXT: Loop %bb3: Unpredictable max backedge-taken count. |
| ; CHECK-NEXT: Loop %bb3: Predicated backedge-taken count is (1 + (-1 smax %M)) |
| ; CHECK-NEXT: Predicates: |
| ; CHECK-NEXT: {0,+,1}<%bb3> Added Flags: <nssw> |
| define void @test1(i32 %N, i32 %M) { |
| entry: |
| br label %bb3 |
| |
| bb: ; preds = %bb3 |
| %tmp = getelementptr [1000 x i32], [1000 x i32]* @A, i32 0, i16 %i.0 ; <i32*> [#uses=1] |
| store i32 123, i32* %tmp |
| %tmp2 = add i16 %i.0, 1 ; <i32> [#uses=1] |
| br label %bb3 |
| |
| bb3: ; preds = %bb, %entry |
| %i.0 = phi i16 [ 0, %entry ], [ %tmp2, %bb ] ; <i32> [#uses=3] |
| %i.0.ext = sext i16 %i.0 to i32 |
| %tmp3 = icmp sle i32 %i.0.ext, %M ; <i1> [#uses=1] |
| br i1 %tmp3, label %bb, label %bb5 |
| |
| bb5: ; preds = %bb3 |
| br label %return |
| |
| return: ; preds = %bb5 |
| ret void |
| } |
| |
| ; The predicated backedge taken count is: |
| ; (2 + (zext i16 %Start to i32) + ((-2 + (-1 * (sext i16 %Start to i32))) |
| ; smax (-1 + (-1 * %M))) |
| ; ) |
| |
| ; -1 + (-1 * %M) <= (-2 + (-1 * (sext i16 %Start to i32)) |
| ; The predicated backedge taken count is 0. |
| ; From the IR, this is correct since we will bail out at the |
| ; first iteration. |
| |
| |
| ; * -1 + (-1 * %M) > (-2 + (-1 * (sext i16 %Start to i32)) |
| ; or: %M < 1 + (sext i16 %Start to i32) |
| ; |
| ; The predicated backedge taken count is 1 + (zext i16 %Start to i32) - %M |
| ; |
| ; If %M >= MIN_INT + 1, this predicated backedge taken count would be correct (even |
| ; without predicates). However, for %M < MIN_INT this would be an infinite loop. |
| ; In these cases, the {%Start,+,-1} <nusw> predicate would be false, as the |
| ; final value of the expression {%Start,+,-1} expression (%M - 1) would not be |
| ; representable as an i16. |
| |
| ; There is also a limit case here where the value of %M is MIN_INT. In this case |
| ; we still have an infinite loop, since icmp sge %x, MIN_INT will always return |
| ; true. |
| |
| ; CHECK: Classifying expressions for: @test2 |
| |
| ; CHECK: %i.0.ext = sext i16 %i.0 to i32 |
| ; CHECK-NEXT: --> (sext i16 {%Start,+,-1}<%bb3> to i32) |
| ; CHECK: Loop %bb3: Unpredictable backedge-taken count. |
| ; CHECK-NEXT: Loop %bb3: Unpredictable max backedge-taken count. |
| ; 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))) |
| ; CHECK-NEXT: Predicates: |
| ; CHECK-NEXT: {%Start,+,-1}<%bb3> Added Flags: <nssw> |
| |
| define void @test2(i32 %N, i32 %M, i16 %Start) { |
| entry: |
| br label %bb3 |
| |
| bb: ; preds = %bb3 |
| %tmp = getelementptr [1000 x i32], [1000 x i32]* @A, i32 0, i16 %i.0 ; <i32*> [#uses=1] |
| store i32 123, i32* %tmp |
| %tmp2 = sub i16 %i.0, 1 ; <i32> [#uses=1] |
| br label %bb3 |
| |
| bb3: ; preds = %bb, %entry |
| %i.0 = phi i16 [ %Start, %entry ], [ %tmp2, %bb ] ; <i32> [#uses=3] |
| %i.0.ext = sext i16 %i.0 to i32 |
| %tmp3 = icmp sge i32 %i.0.ext, %M ; <i1> [#uses=1] |
| br i1 %tmp3, label %bb, label %bb5 |
| |
| bb5: ; preds = %bb3 |
| br label %return |
| |
| return: ; preds = %bb5 |
| ret void |
| } |
| |