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Avoid undefined behavior in shift operators during constant folding of DIExpressions. #116466

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merged 2 commits into from
Nov 18, 2024
Merged

Avoid undefined behavior in shift operators during constant folding of DIExpressions. #116466

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57f9ef9
Avoid undefined behavior in shift operators during constant folding o…
tahonermann Nov 16, 2024
7e51e85
Address code review comments; use static_cast instead of C style casts.
tahonermann Nov 16, 2024
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6 changes: 4 additions & 2 deletions llvm/lib/IR/DIExpressionOptimizer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -59,12 +59,14 @@ foldOperationIfPossible(uint64_t Const1, uint64_t Const2,
return Const1 - Const2;
}
case dwarf::DW_OP_shl: {
if ((uint64_t)countl_zero(Const1) < Const2)
if (Const2 >= std::numeric_limits<uint64_t>::digits ||
(uint64_t)countl_zero(Const1) < Const2)
return std::nullopt;
return Const1 << Const2;
}
case dwarf::DW_OP_shr: {
if ((uint64_t)countr_zero(Const1) < Const2)
if (Const2 >= std::numeric_limits<uint64_t>::digits ||
(uint64_t)countr_zero(Const1) < Const2)
return std::nullopt;
return Const1 >> Const2;
}
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12 changes: 6 additions & 6 deletions llvm/unittests/IR/MetadataTest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3541,38 +3541,38 @@ TEST_F(DIExpressionTest, Fold) {
ResExpr = DIExpression::get(Context, ResOps);
EXPECT_EQ(E, ResExpr);

// Test a left shift greater than 64.
// Test a left shift greater than 63.
Ops.clear();
Ops.push_back(dwarf::DW_OP_constu);
Ops.push_back(1);
Ops.push_back(dwarf::DW_OP_constu);
Ops.push_back(65);
Ops.push_back(64);
Ops.push_back(dwarf::DW_OP_shl);
Expr = DIExpression::get(Context, Ops);
E = Expr->foldConstantMath();
ResOps.clear();
ResOps.push_back(dwarf::DW_OP_constu);
ResOps.push_back(1);
ResOps.push_back(dwarf::DW_OP_constu);
ResOps.push_back(65);
ResOps.push_back(64);
ResOps.push_back(dwarf::DW_OP_shl);
ResExpr = DIExpression::get(Context, ResOps);
EXPECT_EQ(E, ResExpr);

// Test a right shift greater than 64.
// Test a right shift greater than 63.
Ops.clear();
Ops.push_back(dwarf::DW_OP_constu);
Ops.push_back(1);
Ops.push_back(dwarf::DW_OP_constu);
Ops.push_back(65);
Ops.push_back(64);
Ops.push_back(dwarf::DW_OP_shr);
Expr = DIExpression::get(Context, Ops);
E = Expr->foldConstantMath();
ResOps.clear();
ResOps.push_back(dwarf::DW_OP_constu);
ResOps.push_back(1);
ResOps.push_back(dwarf::DW_OP_constu);
ResOps.push_back(65);
ResOps.push_back(64);
ResOps.push_back(dwarf::DW_OP_shr);
ResExpr = DIExpression::get(Context, ResOps);
EXPECT_EQ(E, ResExpr);
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