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[clang][Interp] Implement __builtin_ffs #72988

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Merged
merged 1 commit into from
Dec 12, 2023
Merged

[clang][Interp] Implement __builtin_ffs #72988

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18 changes: 18 additions & 0 deletions clang/lib/AST/Interp/InterpBuiltin.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -602,6 +602,17 @@ static bool interp__builtin_rotate(InterpState &S, CodePtr OpPC,
return true;
}

static bool interp__builtin_ffs(InterpState &S, CodePtr OpPC,
const InterpFrame *Frame, const Function *Func,
const CallExpr *Call) {
PrimType ArgT = *S.getContext().classify(Call->getArg(0)->getType());
APSInt Value = peekToAPSInt(S.Stk, ArgT);

uint64_t N = Value.countr_zero();
pushInt(S, N == Value.getBitWidth() ? 0 : N + 1);
return true;
}

bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
const CallExpr *Call) {
InterpFrame *Frame = S.Current;
Expand Down Expand Up @@ -803,6 +814,13 @@ bool InterpretBuiltin(InterpState &S, CodePtr OpPC, const Function *F,
return false;
break;

case Builtin::BI__builtin_ffs:
case Builtin::BI__builtin_ffsl:
case Builtin::BI__builtin_ffsll:
if (!interp__builtin_ffs(S, OpPC, Frame, F, Call))
return false;
break;

default:
return false;
}
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10 changes: 10 additions & 0 deletions clang/test/AST/Interp/builtin-functions.cpp
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Expand Up @@ -353,3 +353,13 @@ namespace rotateright {
char rotateright3[__builtin_rotateright32(0x76543210, 22) == 0x50C841D9 ? 1 : -1];
char rotateright4[__builtin_rotateright64(0xFEDCBA9876543210ULL, 55) == 0xB97530ECA86421FDULL ? 1 : -1];
}

namespace ffs {
char ffs1[__builtin_ffs(0) == 0 ? 1 : -1];
char ffs2[__builtin_ffs(1) == 1 ? 1 : -1];
char ffs3[__builtin_ffs(0xfbe71) == 1 ? 1 : -1];
char ffs4[__builtin_ffs(0xfbe70) == 5 ? 1 : -1];
char ffs5[__builtin_ffs(1U << (BITSIZE(int) - 1)) == BITSIZE(int) ? 1 : -1];
char ffs6[__builtin_ffsl(0x10L) == 5 ? 1 : -1];
char ffs7[__builtin_ffsll(0x100LL) == 9 ? 1 : -1];
}