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[mono][interp] Fix mis-sorted SIMD intrinsic tables making entries unreachable#132500

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Merged
lewing merged 2 commits into from
Aug 19, 2026
+28 −11
Merged

[mono][interp] Fix mis-sorted SIMD intrinsic tables making entries unreachable #132500

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c604114
[mono][interp] Fix mis-sorted SIMD intrinsic tables making entries un…
lewing Aug 19, 2026
2fac1aa
Merge commit '029a98f26a9506810140781e88ccb8e45de1cc79' into lewing-f…
lewing Aug 19, 2026
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39 changes: 28 additions & 11 deletions src/mono/mono/mini/interp/transform-simd.c
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Original file line numberDiff line numberDiff line change
Expand Up@@ -43,9 +43,29 @@ simd_intrinsic_compare_by_name (const void *key, const void *value)
return strcmp ((const char*)key, method_name (*(guint16*)value));
}

#ifdef ENABLE_CHECKED_BUILD
// The tables below are searched with mono_binary_search, so an out-of-order entry silently makes
// itself and potentially its neighbors unreachable - the intrinsic is never emitted and we fall
// back to the managed implementation with no other visible symptom. Validate the invariant here
// so that a mis-sorted table fails loudly in checked builds instead of quietly losing performance.
static void
check_intrins_sorted (guint16 *intrinsics, int size)
{
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int count = size / sizeof (guint16);
for (int i = 1; i < count; i++) {
const char *prev = method_name (intrinsics [i - 1]), *cur = method_name (intrinsics [i]);
g_assertf (strcmp (prev, cur) < 0,
"interp SIMD intrinsic table is not in ASCII order: '%s' must not precede '%s'", prev, cur);
}
}
#endif

static int
lookup_intrins (guint16 *intrinsics, int size, const char *cmethod_name)
{
#ifdef ENABLE_CHECKED_BUILD
check_intrins_sorted (intrinsics, size);
#endif
guint16 *result = mono_binary_search (cmethod_name, intrinsics, size / sizeof (guint16), sizeof (guint16), &simd_intrinsic_compare_by_name);

if (result == NULL)
Expand DownExpand Up@@ -74,8 +94,8 @@ static guint16 sri_vector128_methods [] = {
SN_AsUInt32,
SN_AsUInt64,
SN_AsVector,
SN_AsVector4,
SN_AsVector128,
SN_AsVector4,
SN_ConditionalSelect,
SN_Create,
SN_CreateScalar,
Expand DownExpand Up@@ -173,12 +193,15 @@ static guint16 packedsimd_alias_methods [] = {
SN_ShiftLeft,
SN_ShiftRightArithmetic,
SN_ShiftRightLogical,
SN_Store,
SN_StoreUnsafe,
SN_Subtract,
SN_SubtractSaturate,
SN_Sqrt,
SN_SquareRoot,
// NOTE: Store/StoreUnsafe are deliberately absent. PackedSimd.Store's operands are reversed
// relative to Vector128's - PackedSimd.Store(T* address, Vector128<T> source) versus
// Vector128.Store(this Vector128<T> source, T* destination) - and this path only renames
// the method, with emit_common_simd_epilogue assigning sregs in signature order. Aliasing
// them would pass the vector where the destination address is expected and corrupt memory.
SN_Subtract,
SN_SubtractSaturate,
SN_Truncate,
SN_WidenLower,
SN_WidenUpper,
Expand DownExpand Up@@ -1251,12 +1274,6 @@ emit_sri_packedsimd (TransformData *td, MonoMethod *cmethod, MonoMethodSignature
case SN_SquareRoot:
cmethod_name = "Sqrt";
break;
case SN_Store:
case SN_StoreUnsafe:
if (csignature->param_count != 2)
return FALSE;
cmethod_name = "Store";
break;
case SN_Add:
case SN_AddSaturate:
case SN_AndNot:
Expand Down