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