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[LazyValueInfo] PR33357 prevent infinite recursion on BinaryOperator

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Summary:
It is possible for LVI to encounter instructions that are not in valid
SSA form and reference themselves. One example is the following:
  %tmp4 = and i1 %tmp4, undef
Before this patch LVI would recurse until running out of stack memory
and crashed.  This patch marks these self-referential instructions as
Overdefined and aborts analysis on the instruction.

Fixes https://bugs.llvm.org/show_bug.cgi?id=33357

Reviewers: craig.topper, anna, efriedma, dberlin, sebpop, kuhar

Reviewed by: dberlin

Subscribers: uabelho, spatel, a.elovikov, fhahn, eli.friedman, mzolotukhin, spop, evandro, davide, llvm-commits

Differential Revision: https://reviews.llvm.org/D34135

llvm-svn: 327432
This commit is contained in:
Brian M. Rzycki 2018-03-13 18:14:10 +00:00
parent 4361f2f333
commit 409c4a1d03
2 changed files with 48 additions and 3 deletions
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14
lib/Analysis/LazyValueInfo.cpp
View File

@ -1145,9 +1145,17 @@ getValueFromConditionImpl(Value *Val, Value *Cond, bool isTrueDest,
(!isTrueDest && BO->getOpcode() != BinaryOperator::Or))
return ValueLatticeElement::getOverdefined();
auto RHS = getValueFromCondition(Val, BO->getOperand(0), isTrueDest, Visited);
auto LHS = getValueFromCondition(Val, BO->getOperand(1), isTrueDest, Visited);
return intersect(RHS, LHS);
// Prevent infinite recursion if Cond references itself as in this example:
// Cond: "%tmp4 = and i1 %tmp4, undef"
// BL: "%tmp4 = and i1 %tmp4, undef"
// BR: "i1 undef"
Value *BL = BO->getOperand(0);
Value *BR = BO->getOperand(1);
if (BL == Cond || BR == Cond)
return ValueLatticeElement::getOverdefined();
return intersect(getValueFromCondition(Val, BL, isTrueDest, Visited),
getValueFromCondition(Val, BR, isTrueDest, Visited));
}
static ValueLatticeElement

37
test/Transforms/JumpThreading/PR33357-lvi-recursion.ll Normal file
View File

@ -0,0 +1,37 @@
; RUN: opt -S -jump-threading -verify -o - %s | FileCheck %s
@a = external global i16, align 1
; CHECK-LABEL: f
; CHECK: bb6:
; CHECK: bb2:
; CHECK: bb3:
; CHECK-NOT: bb0:
; CHECK-NOT: bb1:
; CHECK-NOT: bb4:
; CHECK-NOT: bb5:
define void @f(i32 %p1) {
bb0:
%0 = icmp eq i32 %p1, 0
br i1 undef, label %bb6, label %bb1
bb1:
br label %bb2
bb2:
%1 = phi i1 [ %0, %bb1 ], [ %2, %bb4 ]
%2 = and i1 %1, undef
br i1 %2, label %bb3, label %bb4
bb3:
store i16 undef, i16* @a, align 1
br label %bb4
bb4:
br i1 %0, label %bb2, label %bb5
bb5:
unreachable
bb6:
ret void
}