Math: FFT-multi: Add Xtensa HiFi versions for hot code functions

This patch adds HiFi3 versions for functions dft3_32() and
fft_multi_execute_32(). The functions are implemented to
fft_multi_hifi3.c and the generic versions are moved to
fft_multi_generic.c.

in MTL platform the optimization saves 119 MCPS, from 237 MCPS
to 118 MCPS. The test was done with script run:

scripts/rebuild-testbench.sh -p mtl
scripts/sof-testbench-helper.sh -x -m stft_process_1536_240_ \
  -p profile-stft_process.txt

The above STFT used FFT length of 1536 with hop 240.

Signed-off-by: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>

Author: singalsu

src/include/sof/math/fft.h

@@ -98,8 +98,8 @@ void mod_fft_multi_plan_free(struct processing_module *mod, struct fft_multi_pla
 
 /**
  * dft3_32() - Discrete Fourier Transform (DFT) for size 3.
- * @param input: Pointer to complex values input array, Q1.31
- * @param output: Pointer to complex values output array, Q3.29
+ * @param input: Pointer to complex values input array, Q1.31.
+ * @param output: Pointer to complex values output array, Q1.31, scaled down by 1/3.
  *
  * This function is useful for calculating some non power of two FFTs. E.g. the
  * FFT for size 1536 is done with three 512 size FFTs and one 3 size DFT.

src/math/fft/CMakeLists.txt

@@ -11,7 +11,7 @@ if(CONFIG_MATH_32BIT_FFT)
 endif()
 
 if(CONFIG_MATH_FFT_MULTI)
-  list(APPEND base_files fft_multi.c)
+  list(APPEND base_files fft_multi.c fft_multi_generic.c fft_multi_hifi3.c)
 endif()
 
 is_zephyr(zephyr)

src/math/fft/fft_multi.c

@@ -19,11 +19,6 @@ LOG_MODULE_REGISTER(math_fft_multi, CONFIG_SOF_LOG_LEVEL);
 SOF_DEFINE_REG_UUID(math_fft_multi);
 DECLARE_TR_CTX(math_fft_multi_tr, SOF_UUID(math_fft_multi_uuid), LOG_LEVEL_INFO);
 
-/* Constants for size 3 DFT */
-#define DFT3_COEFR	-1073741824	/* int32(-0.5 * 2^31) */
-#define DFT3_COEFI	1859775393	/* int32(sqrt(3) / 2 * 2^31) */
-#define DFT3_SCALE	715827883	/* int32(1/3*2^31) */
-
 struct fft_multi_plan *mod_fft_multi_plan_new(struct processing_module *mod, void *inb,
 					      void *outb, uint32_t size, int bits)
 {
@@ -143,152 +138,3 @@ void mod_fft_multi_plan_free(struct processing_module *mod, struct fft_multi_pla
 	mod_free(mod, plan->bit_reverse_idx);
 	mod_free(mod, plan);
 }
-
-void dft3_32(struct icomplex32 *x_in, struct icomplex32 *y)
-{
-	const struct icomplex32 c0 = {DFT3_COEFR, -DFT3_COEFI};
-	const struct icomplex32 c1 = {DFT3_COEFR,  DFT3_COEFI};
-	struct icomplex32 x[3];
-	struct icomplex32 p1, p2, sum;
-	int i;
-
-	for (i = 0; i < 3; i++) {
-		x[i].real = Q_MULTSR_32X32((int64_t)x_in[i].real, DFT3_SCALE, 31, 31, 31);
-		x[i].imag = Q_MULTSR_32X32((int64_t)x_in[i].imag, DFT3_SCALE, 31, 31, 31);
-	}
-
-	/*
-	 *      | 1   1   1 |
-	 * c =  | 1  c0  c1 | , x = [ x0 x1 x2 ]
-	 *      | 1  c1  c0 |
-	 *
-	 * y(0) = c(0,0) * x(0) + c(1,0) * x(1) + c(2,0) * x(0)
-	 * y(1) = c(0,1) * x(0) + c(1,1) * x(1) + c(2,1) * x(0)
-	 * y(2) = c(0,2) * x(0) + c(1,2) * x(1) + c(2,2) * x(0)
-	 */
-
-	/* y(0) = 1 * x(0) + 1 * x(1) + 1 * x(2) */
-	icomplex32_adds(&x[0], &x[1], &sum);
-	icomplex32_adds(&x[2], &sum, &y[0]);
-
-	/* y(1) = 1 * x(0) + c0 * x(1) + c1 * x(2) */
-	icomplex32_mul(&c0, &x[1], &p1);
-	icomplex32_mul(&c1, &x[2], &p2);
-	icomplex32_adds(&p1, &p2, &sum);
-	icomplex32_adds(&x[0], &sum, &y[1]);
-
-	/* y(2) = 1 * x(0) + c1 * x(1) + c0 * x(2) */
-	icomplex32_mul(&c1, &x[1], &p1);
-	icomplex32_mul(&c0, &x[2], &p2);
-	icomplex32_adds(&p1, &p2, &sum);
-	icomplex32_adds(&x[0], &sum, &y[2]);
-}
-
-void fft_multi_execute_32(struct fft_multi_plan *plan, bool ifft)
-{
-	struct icomplex32 x[FFT_MULTI_COUNT_MAX];
-	struct icomplex32 y[FFT_MULTI_COUNT_MAX];
-	struct icomplex32 t, c;
-	int i, j, k, m;
-
-	/* Handle 2^N FFT */
-	if (plan->num_ffts == 1) {
-		memset(plan->outb32, 0, plan->fft_size * sizeof(struct icomplex32));
-		fft_execute_32(plan->fft_plan[0], ifft);
-		return;
-	}
-
-#ifdef DEBUG_DUMP_TO_FILE
-	FILE *fh1 = fopen("debug_fft_multi_int1.txt", "w");
-	FILE *fh2 = fopen("debug_fft_multi_int2.txt", "w");
-	FILE *fh3 = fopen("debug_fft_multi_twiddle.txt", "w");
-	FILE *fh4 = fopen("debug_fft_multi_dft_out.txt", "w");
-#endif
-
-	/* convert to complex conjugate for IFFT */
-	if (ifft) {
-		for (i = 0; i < plan->total_size; i++)
-			icomplex32_conj(&plan->inb32[i]);
-	}
-
-	/* Copy input buffers */
-	k = 0;
-	for (i = 0; i < plan->fft_size; i++)
-		for (j = 0; j < plan->num_ffts; j++)
-			plan->tmp_i32[j][i] = plan->inb32[k++];
-
-	/* Clear output buffers and call individual FFTs*/
-	for (j = 0; j < plan->num_ffts; j++) {
-		memset(&plan->tmp_o32[j][0], 0, plan->fft_size * sizeof(struct icomplex32));
-		fft_execute_32(plan->fft_plan[j], 0);
-	}
-
-#ifdef DEBUG_DUMP_TO_FILE
-	for (j = 0; j < plan->num_ffts; j++)
-		for (i = 0; i < plan->fft_size; i++)
-			fprintf(fh1, "%d %d\n", plan->tmp_o32[j][i].real, plan->tmp_o32[j][i].imag);
-#endif
-
-	/* Multiply with twiddle factors */
-	m = FFT_MULTI_TWIDDLE_SIZE / 2 / plan->fft_size;
-	for (j = 1; j < plan->num_ffts; j++) {
-		for (i = 0; i < plan->fft_size; i++) {
-			c = plan->tmp_o32[j][i];
-			k = j * i * m;
-			t.real = multi_twiddle_real_32[k];
-			t.imag = multi_twiddle_imag_32[k];
-			//fprintf(fh3, "%d %d\n", t.real, t.imag);
-			icomplex32_mul(&t, &c, &plan->tmp_o32[j][i]);
-		}
-	}
-
-#ifdef DEBUG_DUMP_TO_FILE
-	for (j = 0; j < plan->num_ffts; j++)
-		for (i = 0; i < plan->fft_size; i++)
-			fprintf(fh2, "%d %d\n", plan->tmp_o32[j][i].real, plan->tmp_o32[j][i].imag);
-#endif
-
-	/* DFT of size 3 */
-	j = plan->fft_size;
-	k = 2 * plan->fft_size;
-	for (i = 0; i < plan->fft_size; i++) {
-		x[0] = plan->tmp_o32[0][i];
-		x[1] = plan->tmp_o32[1][i];
-		x[2] = plan->tmp_o32[2][i];
-		dft3_32(x, y);
-		plan->outb32[i] = y[0];
-		plan->outb32[i + j] = y[1];
-		plan->outb32[i + k] = y[2];
-	}
-
-#ifdef DEBUG_DUMP_TO_FILE
-	for (i = 0; i < plan->total_size; i++)
-		fprintf(fh4, "%d %d\n",  plan->outb32[i].real, plan->outb32[i].imag);
-#endif
-
-	/* shift back for IFFT */
-
-	/* TODO: Check if time shift method for IFFT is more efficient or more accurate
-	 * tmp = 1 / N * fft(X);
-	 * x = tmp([1 N:-1:2])
-	 */
-	if (ifft) {
-		/*
-		 * no need to divide N as it is already done in the input side
-		 * for Q1.31 format. Instead, we need to multiply N to compensate
-		 * the shrink we did in the FFT transform.
-		 */
-		for (i = 0; i < plan->total_size; i++) {
-			/* Need to negate imag part to match reference */
-			plan->outb32[i].imag = -plan->outb32[i].imag;
-			icomplex32_shift(&plan->outb32[i], plan->fft_plan[0]->len,
-					 &plan->outb32[i]);
-			plan->outb32[i].real = sat_int32((int64_t)plan->outb32[i].real * 3);
-			plan->outb32[i].imag = sat_int32((int64_t)plan->outb32[i].imag * 3);
-		}
-	}
-
-#ifdef DEBUG_DUMP_TO_FILE
-	fclose(fh1); fclose(fh2); fclose(fh3); fclose(fh4);
-#endif
-}

src/math/fft/fft_multi_generic.c

@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: BSD-3-Clause
+//
+// Copyright(c) 2025-2026 Intel Corporation.
+//
+// Author: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>
+
+#include <sof/audio/format.h>
+#include <sof/math/icomplex32.h>
+#include <sof/common.h>
+#include <sof/math/fft.h>
+
+#ifdef DEBUG_DUMP_TO_FILE
+#include <stdio.h>
+#endif
+
+/* Twiddle factor tables defined in fft_multi.c via twiddle_3072_32.h */
+#define FFT_MULTI_TWIDDLE_SIZE 2048
+extern const int32_t multi_twiddle_real_32[];
+extern const int32_t multi_twiddle_imag_32[];
+
+/* Constants for size 3 DFT */
+#define DFT3_COEFR -1073741824 /* int32(-0.5 * 2^31) */
+#define DFT3_COEFI 1859775393  /* int32(sqrt(3) / 2 * 2^31) */
+#define DFT3_SCALE 715827883   /* int32(1/3*2^31) */
+
+#ifdef FFT_GENERIC
+
+void dft3_32(struct icomplex32 *x_in, struct icomplex32 *y)
+{
+	const struct icomplex32 c0 = {DFT3_COEFR, -DFT3_COEFI};
+	const struct icomplex32 c1 = {DFT3_COEFR, DFT3_COEFI};
+	struct icomplex32 x[3];
+	struct icomplex32 p1, p2, sum;
+	int i;
+
+	for (i = 0; i < 3; i++) {
+		x[i].real = Q_MULTSR_32X32((int64_t)x_in[i].real, DFT3_SCALE, 31, 31, 31);
+		x[i].imag = Q_MULTSR_32X32((int64_t)x_in[i].imag, DFT3_SCALE, 31, 31, 31);
+	}
+
+	/*
+	 *      | 1   1   1 |
+	 * c =  | 1  c0  c1 | , x = [ x0 x1 x2 ]
+	 *      | 1  c1  c0 |
+	 *
+	 * y(0) = c(0,0) * x(0) + c(1,0) * x(1) + c(2,0) * x(2)
+	 * y(1) = c(0,1) * x(0) + c(1,1) * x(1) + c(2,1) * x(2)
+	 * y(2) = c(0,2) * x(0) + c(1,2) * x(1) + c(2,2) * x(2)
+	 */
+
+	/* y(0) = 1 * x(0) + 1 * x(1) + 1 * x(2) */
+	icomplex32_adds(&x[0], &x[1], &sum);
+	icomplex32_adds(&x[2], &sum, &y[0]);
+
+	/* y(1) = 1 * x(0) + c0 * x(1) + c1 * x(2) */
+	icomplex32_mul(&c0, &x[1], &p1);
+	icomplex32_mul(&c1, &x[2], &p2);
+	icomplex32_adds(&p1, &p2, &sum);
+	icomplex32_adds(&x[0], &sum, &y[1]);
+
+	/* y(2) = 1 * x(0) + c1 * x(1) + c0 * x(2) */
+	icomplex32_mul(&c1, &x[1], &p1);
+	icomplex32_mul(&c0, &x[2], &p2);
+	icomplex32_adds(&p1, &p2, &sum);
+	icomplex32_adds(&x[0], &sum, &y[2]);
+}
+
+void fft_multi_execute_32(struct fft_multi_plan *plan, bool ifft)
+{
+	struct icomplex32 x[FFT_MULTI_COUNT_MAX];
+	struct icomplex32 y[FFT_MULTI_COUNT_MAX];
+	struct icomplex32 t, c;
+	int i, j, k, m;
+
+	/* Handle 2^N FFT */
+	if (plan->num_ffts == 1) {
+		memset(plan->outb32, 0, plan->fft_size * sizeof(struct icomplex32));
+		fft_execute_32(plan->fft_plan[0], ifft);
+		return;
+	}
+
+#ifdef DEBUG_DUMP_TO_FILE
+	FILE *fh1 = fopen("debug_fft_multi_int1.txt", "w");
+	FILE *fh2 = fopen("debug_fft_multi_int2.txt", "w");
+	FILE *fh3 = fopen("debug_fft_multi_twiddle.txt", "w");
+	FILE *fh4 = fopen("debug_fft_multi_dft_out.txt", "w");
+#endif
+
+	/* convert to complex conjugate for IFFT */
+	if (ifft) {
+		for (i = 0; i < plan->total_size; i++)
+			icomplex32_conj(&plan->inb32[i]);
+	}
+
+	/* Copy input buffers */
+	k = 0;
+	for (i = 0; i < plan->fft_size; i++)
+		for (j = 0; j < plan->num_ffts; j++)
+			plan->tmp_i32[j][i] = plan->inb32[k++];
+
+	/* Clear output buffers and call individual FFTs*/
+	for (j = 0; j < plan->num_ffts; j++) {
+		memset(&plan->tmp_o32[j][0], 0, plan->fft_size * sizeof(struct icomplex32));
+		fft_execute_32(plan->fft_plan[j], 0);
+	}
+
+#ifdef DEBUG_DUMP_TO_FILE
+	for (j = 0; j < plan->num_ffts; j++)
+		for (i = 0; i < plan->fft_size; i++)
+			fprintf(fh1, "%d %d\n", plan->tmp_o32[j][i].real, plan->tmp_o32[j][i].imag);
+#endif
+
+	/* Multiply with twiddle factors */
+	m = FFT_MULTI_TWIDDLE_SIZE / 2 / plan->fft_size;
+	for (j = 1; j < plan->num_ffts; j++) {
+		for (i = 0; i < plan->fft_size; i++) {
+			c = plan->tmp_o32[j][i];
+			k = j * i * m;
+			t.real = multi_twiddle_real_32[k];
+			t.imag = multi_twiddle_imag_32[k];
+			// fprintf(fh3, "%d %d\n", t.real, t.imag);
+			icomplex32_mul(&t, &c, &plan->tmp_o32[j][i]);
+		}
+	}
+
+#ifdef DEBUG_DUMP_TO_FILE
+	for (j = 0; j < plan->num_ffts; j++)
+		for (i = 0; i < plan->fft_size; i++)
+			fprintf(fh2, "%d %d\n", plan->tmp_o32[j][i].real, plan->tmp_o32[j][i].imag);
+#endif
+
+	/* DFT of size 3 */
+	j = plan->fft_size;
+	k = 2 * plan->fft_size;
+	for (i = 0; i < plan->fft_size; i++) {
+		x[0] = plan->tmp_o32[0][i];
+		x[1] = plan->tmp_o32[1][i];
+		x[2] = plan->tmp_o32[2][i];
+		dft3_32(x, y);
+		plan->outb32[i] = y[0];
+		plan->outb32[i + j] = y[1];
+		plan->outb32[i + k] = y[2];
+	}
+
+#ifdef DEBUG_DUMP_TO_FILE
+	for (i = 0; i < plan->total_size; i++)
+		fprintf(fh4, "%d %d\n", plan->outb32[i].real, plan->outb32[i].imag);
+#endif
+
+	/* shift back for IFFT */
+
+	/* TODO: Check if time shift method for IFFT is more efficient or more accurate
+	 * tmp = 1 / N * fft(X);
+	 * x = tmp([1 N:-1:2])
+	 */
+	if (ifft) {
+		/*
+		 * no need to divide N as it is already done in the input side
+		 * for Q1.31 format. Instead, we need to multiply N to compensate
+		 * the shrink we did in the FFT transform.
+		 */
+		for (i = 0; i < plan->total_size; i++) {
+			/* Need to negate imag part to match reference */
+			plan->outb32[i].imag = -plan->outb32[i].imag;
+			icomplex32_shift(&plan->outb32[i], plan->fft_plan[0]->len,
+					 &plan->outb32[i]);
+			plan->outb32[i].real = sat_int32((int64_t)plan->outb32[i].real * 3);
+			plan->outb32[i].imag = sat_int32((int64_t)plan->outb32[i].imag * 3);
+		}
+	}
+
+#ifdef DEBUG_DUMP_TO_FILE
+	fclose(fh1);
+	fclose(fh2);
+	fclose(fh3);
+	fclose(fh4);
+#endif
+}
+
+#endif /* FFT_GENERIC */