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[InstCombine] Don't crash on out of bounds shifts

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Differential Revision: https://reviews.llvm.org/D40649



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@319761 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Igor Laevsky 2017-12-05 12:18:15 +00:00
parent f071b970e4
commit b8aa60d240
2 changed files with 50 additions and 13 deletions
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30
lib/Analysis/ValueTracking.cpp
View File

@ -548,7 +548,7 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
m_BitCast(m_Specific(V))));
CmpInst::Predicate Pred;
ConstantInt *C;
uint64_t C;
// assume(v = a)
if (match(Arg, m_c_ICmp(Pred, m_V, m_Value(A))) &&
Pred == ICmpInst::ICMP_EQ && isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
@ -650,51 +650,55 @@ static void computeKnownBitsFromAssume(const Value *V, KnownBits &Known,
} else if (match(Arg, m_c_ICmp(Pred, m_Shl(m_V, m_ConstantInt(C)),
m_Value(A))) &&
Pred == ICmpInst::ICMP_EQ &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
C < BitWidth) {
KnownBits RHSKnown(BitWidth);
computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
// For those bits in RHS that are known, we can propagate them to known
// bits in V shifted to the right by C.
RHSKnown.Zero.lshrInPlace(C->getZExtValue());
RHSKnown.Zero.lshrInPlace(C);
Known.Zero |= RHSKnown.Zero;
RHSKnown.One.lshrInPlace(C->getZExtValue());
RHSKnown.One.lshrInPlace(C);
Known.One |= RHSKnown.One;
// assume(~(v << c) = a)
} else if (match(Arg, m_c_ICmp(Pred, m_Not(m_Shl(m_V, m_ConstantInt(C))),
m_Value(A))) &&
Pred == ICmpInst::ICMP_EQ &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
C < BitWidth) {
KnownBits RHSKnown(BitWidth);
computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
// For those bits in RHS that are known, we can propagate them inverted
// to known bits in V shifted to the right by C.
RHSKnown.One.lshrInPlace(C->getZExtValue());
RHSKnown.One.lshrInPlace(C);
Known.Zero |= RHSKnown.One;
RHSKnown.Zero.lshrInPlace(C->getZExtValue());
RHSKnown.Zero.lshrInPlace(C);
Known.One |= RHSKnown.Zero;
// assume(v >> c = a)
} else if (match(Arg,
m_c_ICmp(Pred, m_Shr(m_V, m_ConstantInt(C)),
m_Value(A))) &&
Pred == ICmpInst::ICMP_EQ &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
C < BitWidth) {
KnownBits RHSKnown(BitWidth);
computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
// For those bits in RHS that are known, we can propagate them to known
// bits in V shifted to the right by C.
Known.Zero |= RHSKnown.Zero << C->getZExtValue();
Known.One |= RHSKnown.One << C->getZExtValue();
Known.Zero |= RHSKnown.Zero << C;
Known.One |= RHSKnown.One << C;
// assume(~(v >> c) = a)
} else if (match(Arg, m_c_ICmp(Pred, m_Not(m_Shr(m_V, m_ConstantInt(C))),
m_Value(A))) &&
Pred == ICmpInst::ICMP_EQ &&
isValidAssumeForContext(I, Q.CxtI, Q.DT)) {
isValidAssumeForContext(I, Q.CxtI, Q.DT) &&
C < BitWidth) {
KnownBits RHSKnown(BitWidth);
computeKnownBits(A, RHSKnown, Depth+1, Query(Q, I));
// For those bits in RHS that are known, we can propagate them inverted
// to known bits in V shifted to the right by C.
Known.Zero |= RHSKnown.One << C->getZExtValue();
Known.One |= RHSKnown.Zero << C->getZExtValue();
Known.Zero |= RHSKnown.One << C;
Known.One |= RHSKnown.Zero << C;
// assume(v >=_s c) where c is non-negative
} else if (match(Arg, m_ICmp(Pred, m_V, m_Value(A))) &&
Pred == ICmpInst::ICMP_SGE &&

33
test/Transforms/InstCombine/out-of-bounds-indexes.ll Normal file
View File

@ -0,0 +1,33 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -instcombine -S | FileCheck %s
; Check that we don't crash on unreasonable constant indexes
define i32 @test_out_of_bounds(i32 %a, i1 %x, i1 %y) {
; CHECK-LABEL: @test_out_of_bounds(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[AND1:%.*]] = and i32 [[A:%.*]], 3
; CHECK-NEXT: tail call void @llvm.assume(i1 false)
; CHECK-NEXT: ret i32 [[AND1]]
;
entry:
%and1 = and i32 %a, 3
%B = lshr i32 %and1, -2147483648
%cmp = icmp eq i32 %B, 1
tail call void @llvm.assume(i1 %cmp)
ret i32 %and1
}
define i128 @test_non64bit(i128 %a) {
; CHECK-LABEL: @test_non64bit(
; CHECK-NEXT: [[AND1:%.*]] = and i128 [[A:%.*]], 3
; CHECK-NEXT: tail call void @llvm.assume(i1 false)
; CHECK-NEXT: ret i128 [[AND1]]
;
%and1 = and i128 %a, 3
%B = lshr i128 %and1, -1
%cmp = icmp eq i128 %B, 1
tail call void @llvm.assume(i1 %cmp)
ret i128 %and1
}
declare void @llvm.assume(i1)