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Fix signed integer overflow in MakeKernelParams8bit #373

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Fix signed integer overflow in MakeKernelParams8bit #373

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ab43007
Initial upload.
wangw-1991 Jun 25, 2026
781542c
Resolve comments.
wangw-1991 Jul 21, 2026
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8 changes: 7 additions & 1 deletion ruy/kernel_common.h
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Original file line number Diff line number Diff line change
Expand Up @@ -177,7 +177,13 @@ void MakeKernelParams8bit(const PMat<std::int8_t>& lhs,
params->rhs_zero_point = rhs.zero_point;
params->dst_zero_point = dst->zero_point;
params->depth = depth;
params->prod_zp_depth = lhs.zero_point * rhs.zero_point * depth;
// prod_zp_depth intentionally relies on two's-complement wraparound to match
// the wrapping arithmetic performed by the asm kernels. Compute it in unsigned
// so the overflow is well-defined.
params->prod_zp_depth = static_cast<std::int32_t>(
static_cast<std::uint32_t>(lhs.zero_point) *
static_cast<std::uint32_t>(rhs.zero_point) *
static_cast<std::uint32_t>(depth));
params->flags |= RUY_ASM_FLAG_NEEDS_LEFT_SHIFT;
if (mul_params.multiplier_fixedpoint_perchannel()) {
// Temporary release-assert to debug some crashes in an application.
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