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ggml : avoid UB in gemm ukernel + tests #19642

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Merged
ggerganov merged 1 commit into from
Feb 15, 2026
Merged

ggml : avoid UB in gemm ukernel + tests #19642

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57 changes: 27 additions & 30 deletions ggml/src/ggml-cpu/simd-gemm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,6 @@

// Computes C[M x N] += A[M x K] * B[K x N]

#include "ggml-cpu-impl.h"
#include "vec.h"
#include "common.h"
#include "simd-mappings.h"

// TODO: add support for sizeless vector types
Expand All @@ -23,44 +20,38 @@
static constexpr int GEMM_RN = 2;
#endif

#if defined(__GNUC__) && !defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Waggressive-loop-optimizations"
#endif

template <int RM, int RN>
static inline void simd_gemm_ukernel(
float * GGML_RESTRICT C,
const float * GGML_RESTRICT A,
const float * GGML_RESTRICT B,
int64_t K, int64_t N,
int64_t ii, int64_t jj)
int K, int N)
{
static constexpr int KN = GGML_F32_EPR;

GGML_F32_VEC acc[RM][RN];
for (int i = 0; i < RM; i++) {
for (int64_t i = 0; i < RM; i++) {
for (int r = 0; r < RN; r++) {
acc[i][r] = GGML_F32_VEC_LOAD(C + (ii + i) * N + jj + r * KN);
acc[i][r] = GGML_F32_VEC_LOAD(C + i * N + r * KN);
}
}

for (int64_t kk = 0; kk < K; kk++) {
GGML_F32_VEC Bv[RN];
for (int r = 0; r < RN; r++) {
Bv[r] = GGML_F32_VEC_LOAD(B + kk * N + jj + r * KN);
Bv[r] = GGML_F32_VEC_LOAD(B + kk * N + r * KN);
}
for (int i = 0; i < RM; i++) {
GGML_F32_VEC p = GGML_F32_VEC_SET1(A[(ii + i) * K + kk]);
for (int64_t i = 0; i < RM; i++) {
GGML_F32_VEC p = GGML_F32_VEC_SET1(A[i * K + kk]);
for (int r = 0; r < RN; r++) {
acc[i][r] = GGML_F32_VEC_FMA(acc[i][r], Bv[r], p);
}
}
}

for (int i = 0; i < RM; i++) {
for (int64_t i = 0; i < RM; i++) {
for (int r = 0; r < RN; r++) {
GGML_F32_VEC_STORE(C + (ii + i) * N + jj + r * KN, acc[i][r]);
GGML_F32_VEC_STORE(C + i * N + r * KN, acc[i][r]);
}
}
}
Expand All @@ -70,46 +61,52 @@ static void simd_gemm(
float * GGML_RESTRICT C,
const float * GGML_RESTRICT A,
const float * GGML_RESTRICT B,
int64_t M, int64_t K, int64_t N)
int M, int K, int N)
{
static constexpr int KN = GGML_F32_EPR;

int64_t ii = 0;
for (; ii + GEMM_RM <= M; ii += GEMM_RM) {
int64_t jj = 0;
for (; jj + GEMM_RN * KN <= N; jj += GEMM_RN * KN) {
simd_gemm_ukernel<GEMM_RM, GEMM_RN>(C, A, B, K, N, ii, jj);
simd_gemm_ukernel<GEMM_RM, GEMM_RN>(C + jj, A, B + jj, K, N);
}
for (; jj + KN <= N; jj += KN) {
simd_gemm_ukernel<GEMM_RM, 1>(C, A, B, K, N, ii, jj);
simd_gemm_ukernel<GEMM_RM, 1>(C + jj, A, B + jj, K, N);
}
for (; jj < N; jj++) {
for (int i = 0; i < GEMM_RM; i++) {
float a = C[(ii + i) * N + jj];
for (int64_t i = 0; i < GEMM_RM; i++) {
float a = C[i * N + jj];
for (int64_t kk = 0; kk < K; kk++) {
a += A[(ii + i) * K + kk] * B[kk * N + jj];
a += A[i + kk] * B[kk * N + jj];
}
C[(ii + i) * N + jj] = a;
C[i * N + jj] = a;
}
}

A += GEMM_RM * K;
C += GEMM_RM * N;
}

// Tail rows: one at a time
for (; ii < M; ii++) {
int64_t jj = 0;
for (; jj + GEMM_RN * KN <= N; jj += GEMM_RN * KN) {
simd_gemm_ukernel<1, GEMM_RN>(C, A, B, K, N, ii, jj);
simd_gemm_ukernel<1, GEMM_RN>(C + jj, A, B + jj, K, N);
}
for (; jj + KN <= N; jj += KN) {
simd_gemm_ukernel<1, 1>(C, A, B, K, N, ii, jj);
simd_gemm_ukernel<1, 1>(C + jj, A, B + jj, K, N);
}
for (; jj < N; jj++) {
float a = C[ii * N + jj];
float a = C[jj];
for (int64_t kk = 0; kk < K; kk++) {
a += A[ii * K + kk] * B[kk * N + jj];
a += A[kk] * B[kk * N + jj];
}
C[ii * N + jj] = a;
C[jj] = a;
}

A += K;
C += N;
}
}

Expand All @@ -123,7 +120,7 @@ static void simd_gemm(
float * GGML_RESTRICT C,
const float * GGML_RESTRICT A,
const float * GGML_RESTRICT B,
int64_t M, int64_t K, int64_t N)
int M, int K, int N)
{
for (int64_t i = 0; i < M; i++) {
for (int64_t j = 0; j < N; j++) {
Expand Down
2 changes: 1 addition & 1 deletion tests/test-backend-ops.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -8301,7 +8301,7 @@ static std::vector<std::unique_ptr<test_case>> make_test_cases_eval() {
//for (int kv : { 1, 17, 31, 33, 61, 113, 65, 127, 129, 130, 255, 260, 371, 380, 407, 512, 1024, }) {
for (int kv : { 113, 512, 1024, }) {
if (nr2 != 1 && kv != 512) continue;
for (int nb : { 1, 3, 32, 35, }) {
for (int nb : { 1, 3, 32, 75, }) {
for (ggml_prec prec : {GGML_PREC_F32, GGML_PREC_DEFAULT}) {
if (hsk != 128 && prec == GGML_PREC_DEFAULT) continue;
for (ggml_type type_KV : {GGML_TYPE_F32, GGML_TYPE_F16, GGML_TYPE_BF16, GGML_TYPE_Q8_0, GGML_TYPE_Q4_0}) {
Expand Down
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