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[NFC] Add tests that demonstrate that MustExecute is fundamentally broken 

llvm-svn: 339417
This commit is contained in:
Max Kazantsev 2018-08-10 09:20:46 +00:00
parent 1793bc9f78
commit 4e9def57c7
2 changed files with 160 additions and 0 deletions
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118
llvm/test/Analysis/MustExecute/infinite_loops.ll Normal file
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -disable-output -print-mustexecute %s 2>&1 | FileCheck %s
; Infinite loop.
; TODO: backedge is provably mustexecute, but the analysis does not know this.
define void @test_no_exit_block(i1 %cond, i32 %a, i32 %b) {
; CHECK-LABEL: @test_no_exit_block(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ] ; (mustexec in: loop)
; CHECK-NEXT: br i1 [[COND:%.*]], label [[MAYBE_TAKEN:%.*]], label [[BACKEDGE]] ; (mustexec in: loop)
; FIXME: Should be mustexec in backedge. The current analysis does not handle
; loops without exit blocks at all.
; CHECK-NOT: ; (mustexec in: loop)
; CHECK: maybe_taken:
; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br label [[LOOP]]
;
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]
br i1 %cond, label %maybe_taken, label %backedge
maybe_taken:
%div = sdiv i32 %a, %b
br label %backedge
backedge:
%iv.next = add i32 %iv, 1
br label %loop
}
; Unlike the test before, we can say that backedge is mustexec, which is the
; correct behavior.
define void @test_impossible_exit_on_latch(i1 %cond, i32 %a, i32 %b) {
; CHECK-LABEL: @test_impossible_exit_on_latch(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ] ; (mustexec in: loop)
; CHECK-NEXT: br i1 [[COND:%.*]], label [[MAYBE_TAKEN:%.*]], label [[BACKEDGE]] ; (mustexec in: loop)
; CHECK: maybe_taken:
; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: br label [[BACKEDGE]]
; CHECK: backedge:
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1 ; (mustexec in: loop)
; CHECK-NEXT: br i1 true, label [[LOOP]], label [[EXIT:%.*]] ; (mustexec in: loop)
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]
br i1 %cond, label %maybe_taken, label %backedge
maybe_taken:
%div = sdiv i32 %a, %b
br label %backedge
backedge:
%iv.next = add i32 %iv, 1
br i1 true, label %loop, label %exit
exit:
ret void
}
; FIXME: This code demonstrates a bug. %div should not be mustexec.
define void @test_impossible_exit_in_untaken_block(i1 %cond, i32 %a, i32 %b, i32* %p) {
; CHECK-LABEL: @test_impossible_exit_in_untaken_block(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ] ; (mustexec in: loop)
; CHECK-NEXT: br i1 [[COND:%.*]], label [[MAYBE_TAKEN:%.*]], label [[BACKEDGE]] ; (mustexec in: loop)
; CHECK: maybe_taken:
; FIXME: The block below is NOT always taken!!! Current this example demonstrates a
; bug in current mustexecute analysis.
; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[A:%.*]], [[B:%.*]] ; (mustexec in: loop)
; CHECK-NEXT: store i32 [[DIV]], i32* [[P:%.*]] ; (mustexec in: loop)
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[EXIT:%.*]] ; (mustexec in: loop)
; CHECK: backedge:
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1 ; (mustexec in: loop)
; CHECK-NEXT: br label [[LOOP]] ; (mustexec in: loop)
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]
br i1 %cond, label %maybe_taken, label %backedge
maybe_taken:
%div = sdiv i32 %a, %b
store i32 %div, i32* %p
br i1 true, label %backedge, label %exit
backedge:
%iv.next = add i32 %iv, 1
br label %loop
exit:
ret void
}

42
llvm/test/Transforms/LICM/infinite_loops.ll Normal file
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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -basicaa -licm < %s | FileCheck %s
; RUN: opt -aa-pipeline=basic-aa -passes='require<opt-remark-emit>,loop(licm)' -S %s | FileCheck %s
; FIXME: This test demonstrates a bug in MustExecute analysis. We hoist sdiv
; which can be a division by zero from a block which is never taken.
define void @test_impossible_exit_in_untaken_block(i32 %a, i32 %b, i32* %p) {
; CHECK-LABEL: @test_impossible_exit_in_untaken_block(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[DIV:%.*]] = sdiv i32 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[BACKEDGE:%.*]] ]
; CHECK-NEXT: br i1 false, label [[NEVER_TAKEN:%.*]], label [[BACKEDGE]]
; CHECK: never_taken:
; CHECK-NEXT: br i1 true, label [[BACKEDGE]], label [[EXIT:%.*]]
; CHECK: backedge:
; CHECK-NEXT: [[IV_NEXT]] = add i32 [[IV]], 1
; CHECK-NEXT: br label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: store i32 [[DIV]], i32* [[P:%.*]], align 4
; CHECK-NEXT: ret void
;
entry:
br label %loop
loop:
%iv = phi i32 [ 0, %entry ], [ %iv.next, %backedge ]
br i1 false, label %never_taken, label %backedge
never_taken:
%div = sdiv i32 %a, %b
store i32 %div, i32* %p
br i1 true, label %backedge, label %exit
backedge:
%iv.next = add i32 %iv, 1
br label %loop
exit:
ret void
}