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[clang][bytecode] Fix builtin_memchr with non-0 start index #131633

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Merged
merged 1 commit into from
Mar 17, 2025
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[clang][bytecode] Fix builtin_memchr with non-0 start index #131633

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8 changes: 5 additions & 3 deletions clang/lib/AST/ByteCode/InterpBuiltin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2045,8 +2045,10 @@ static bool interp__builtin_memchr(InterpState &S, CodePtr OpPC,
(ID == Builtin::BIstrchr || ID == Builtin::BI__builtin_strchr);

size_t Index = Ptr.getIndex();
size_t Step = 0;
for (;;) {
const Pointer &ElemPtr = Index > 0 ? Ptr.atIndex(Index) : Ptr;
const Pointer &ElemPtr =
(Index + Step) > 0 ? Ptr.atIndex(Index + Step) : Ptr;

if (!CheckLoad(S, OpPC, ElemPtr))
return false;
Expand All @@ -2060,8 +2062,8 @@ static bool interp__builtin_memchr(InterpState &S, CodePtr OpPC,
if (StopAtZero && V == 0)
break;

++Index;
if (MaxLength && Index == MaxLength->getZExtValue())
++Step;
if (MaxLength && Step == MaxLength->getZExtValue())
break;
}

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5 changes: 5 additions & 0 deletions clang/test/AST/ByteCode/builtin-functions.cpp
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Expand Up @@ -1459,6 +1459,11 @@ namespace Memchr {
constexpr bool b = !memchr("hello", 'h', 3); // both-error {{constant expression}} \
// both-note {{non-constexpr function 'memchr' cannot be used in a constant expression}}

constexpr bool f() {
const char *c = "abcdef";
return __builtin_char_memchr(c + 1, 'f', 1) == nullptr;
}
static_assert(f());
}

namespace Strchr {
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