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[LoopDeletion] Invalidate SCEV after moving instruction. 

LoopDeletion may hoist instructions out of a loop using
makeLoopInvariant without invalidating the SCEV for the moved
instruction.

Moving the instruction to a different block may change its
cached block disposition, so invalidate the cached info.

Fixes #57837.
This commit is contained in:
Florian Hahn 2022-09-23 15:13:30 +01:00
parent 1cd4d63fb9
commit d72eb9c985
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2 changed files with 82 additions and 1 deletions
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8
llvm/lib/Transforms/Scalar/LoopDeletion.cpp
View File

@ -89,11 +89,17 @@ static bool isLoopDead(Loop *L, ScalarEvolution &SE,
if (!AllOutgoingValuesSame)
break;
if (Instruction *I = dyn_cast<Instruction>(incoming))
if (Instruction *I = dyn_cast<Instruction>(incoming)) {
if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator())) {
AllEntriesInvariant = false;
break;
}
if (Changed) {
// Moving I to a different location may change its block disposition,
// so invalidate its SCEV.
SE.forgetValue(I);
}
}
}
}

75
llvm/test/Transforms/LoopDeletion/pr57837-invalidate-scev-after-hoisting.ll Normal file
View File

@ -0,0 +1,75 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -passes='loop(indvars,loop-deletion),verify<scalar-evolution>,print<scalar-evolution>' -S %s 2>&1| FileCheck %s
; Make sure the SCEV for %invar is invalidated properly when the instruction is
; moved by LoopDeletion.
; CHECK: Determining loop execution counts for: @test
; CHECK-NEXT: Loop %inner: backedge-taken count is (405 + %invar)<nuw><nsw>
; CHECK-NEXT: Loop %inner: max backedge-taken count is 405
; CHECK-NEXT: Loop %inner: Predicated backedge-taken count is (405 + %invar)<nuw><nsw>
define void @test() {
; CHECK-LABEL: @test(
; CHECK-NEXT: bb:
; CHECK-NEXT: br label [[OUTER_HEADER:%.*]]
; CHECK: outer.header:
; CHECK-NEXT: br i1 true, label [[INNER_PH:%.*]], label [[OUTER_LATCH:%.*]]
; CHECK: inner.ph:
; CHECK-NEXT: [[INVAR:%.*]] = ashr i32 0, 3
; CHECK-NEXT: br label [[INNER:%.*]]
; CHECK: inner:
; CHECK-NEXT: [[P:%.*]] = phi i32 [ poison, [[INNER_PH]] ], [ [[INVAR]], [[INNER]] ]
; CHECK-NEXT: [[INNER_IV:%.*]] = phi i32 [ 1, [[INNER_PH]] ], [ [[INNER_IV_NEXT:%.*]], [[INNER]] ]
; CHECK-NEXT: [[ADD_1:%.*]] = add i32 [[P]], 30586
; CHECK-NEXT: call void @use(i32 [[ADD_1]])
; CHECK-NEXT: [[INNER_IV_NEXT]] = add nuw nsw i32 [[INNER_IV]], 1
; CHECK-NEXT: [[INVAR_ADD:%.*]] = add i32 [[INVAR]], 407
; CHECK-NEXT: [[INNER_CMP:%.*]] = icmp ult i32 [[INNER_IV_NEXT]], [[INVAR_ADD]]
; CHECK-NEXT: br i1 [[INNER_CMP]], label [[INNER]], label [[INNER_EXIT:%.*]]
; CHECK: inner.exit:
; CHECK-NEXT: [[INVAR_LCSSA:%.*]] = phi i32 [ [[INVAR]], [[INNER]] ]
; CHECK-NEXT: br label [[OUTER_LATCH]]
; CHECK: outer.latch:
; CHECK-NEXT: [[MERGE:%.*]] = phi i32 [ 0, [[OUTER_HEADER]] ], [ [[INVAR_LCSSA]], [[INNER_EXIT]] ]
; CHECK-NEXT: call void @use(i32 [[MERGE]])
; CHECK-NEXT: br label [[EXIT:%.*]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
bb:
br label %outer.header
outer.header: ; preds = %bb19, %bb
%outer.iv = phi i32 [ 0, %bb ], [ %tmp21, %outer.latch ]
%outer.cmp = icmp ult i32 %outer.iv, 400
br i1 %outer.cmp, label %inner.ph, label %outer.latch
inner.ph:
br label %inner
inner:
%p = phi i32 [ poison, %inner.ph ], [ %invar, %inner ]
%inner.iv = phi i32 [ 1, %inner.ph ], [ %inner.iv.next , %inner ]
%add.1 = add i32 %p, 30586
call void @use(i32 %add.1)
%invar = ashr i32 0, 3
%inner.iv.next = add nuw nsw i32 %inner.iv, 1
%invar.add = add i32 %invar, 407
%inner.cmp = icmp slt i32 %inner.iv.next, %invar.add
br i1 %inner.cmp, label %inner, label %inner.exit
inner.exit:
br label %outer.latch
outer.latch:
%merge = phi i32 [ 0, %outer.header ], [ %invar, %inner.exit ]
call void @use(i32 %merge)
%tmp21 = add i32 %outer.iv, 1
br i1 true, label %exit, label %outer.header
exit:
ret void
}
declare void @use(i32)