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Use the global small data pointer #728

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Merged
ckormanyos merged 1 commit into from
Feb 20, 2026
Merged

Use the global small data pointer #728

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19 changes: 16 additions & 3 deletions ref_app/src/math/functions/math_functions_bessel.h
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
///////////////////////////////////////////////////////////////////////////////
// Copyright Christopher Kormanyos 2014 - 2025.
// Copyright Christopher Kormanyos 2014 - 2026.
// Distributed under the Boost Software License,
// Version 1.0. (See accompanying file LICENSE_1_0.txt
// or copy at http://www.boost.org/LICENSE_1_0.txt)
Expand All @@ -22,11 +22,24 @@
// Compute the Taylor series representation of cyl_bessel_j.
// There are no checks on input range or parameter boundaries.

// The following low-precision analysis has been carried out
// for another perspective on small arguments.

// Series[BesselJ[n, x], {x, 0, 7}]
// Normal[%]
// FullSimplify[%]
// Then explicitly take the polynomial part and run it through HornerForm[...].
// The result is the following.
// (1/(3 Gamma[4 + n])) 2^(-7 - n) x^n (384 (1 + n) (2 + n) (3 + n) - x^2 (576 + n (480 + 96 n) + x^2 (36 + 12 n - x^2)))
// This should provide good precision for 32-bit float for arguments having (x/n) <= 3/10.

const T x_half = x / 2;
const T v_plus_one = v + 1;

const T hypergeometric_0f1_term =
math::functions::hypergeometric_0f1(v_plus_one, -(x_half * x_half));
const T hypergeometric_0f1_term
{
math::functions::hypergeometric_0f1(v_plus_one, -(x_half * x_half))
};

using std::pow;
using std::tgamma;
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16 changes: 10 additions & 6 deletions ref_app/target/micros/xtensa_esp32_p4/make/xtensa_esp32_p4.ld
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Expand Up @@ -122,6 +122,7 @@ SECTIONS
*(.data*)
. = ALIGN(4);
KEEP (*(.data*))
_small_ram_begin = .;
*(.sdata)
. = ALIGN(4);
KEEP (*(.sdata))
Expand All @@ -135,18 +136,19 @@ SECTIONS
.bss : ALIGN(4)
{
_bss_begin = .;
*(.bss)
. = ALIGN(4);
KEEP (*(.bss))
*(.bss*)
. = ALIGN(4);
KEEP (*(.bss*))
*(.sbss)
. = ALIGN(4);
KEEP (*(.sbss))
*(.sbss*)
. = ALIGN(4);
KEEP (*(.sbss*))
_small_ram_end = .;
*(.bss)
. = ALIGN(4);
KEEP (*(.bss))
*(.bss*)
. = ALIGN(4);
KEEP (*(.bss*))
_bss_end = .;
} > RAM

Expand Down Expand Up @@ -174,4 +176,6 @@ SECTIONS
printf = 0x4fc00024;

_rom_data_begin = LOADADDR(.data);

_global_pointer = _small_ram_begin + (_small_ram_end - _small_ram_begin) / 2;
}
4 changes: 4 additions & 0 deletions ref_app/target/micros/xtensa_esp32_p4/make/xtensa_esp32_p4_flags.gmk
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Expand Up @@ -21,6 +21,9 @@ TGT_ALLFLAGS = -O2
-march=rv32imafc_zicsr_zifencei_xesppie \
-mabi=ilp32f \
-msmall-data-limit=32 \
-mrelax \
-mrelax \
-fno-common \
-falign-functions=4 \
-fomit-frame-pointer \
-DHP_CORES_SMP_MODE
Expand All @@ -40,6 +43,7 @@ TGT_AFLAGS =

TGT_LDFLAGS = -nostdlib \
-nostartfiles \
$(TGT_ALLFLAGS) \
-Wl,--no-warn-rwx-segments \
-Wl,-z,max-page-size=4096 \
-Wl,-Map,$(APP).map \
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4 changes: 4 additions & 0 deletions ref_app/target/micros/xtensa_esp32_p4/startup/Code/Startup/boot.s
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Expand Up @@ -38,6 +38,7 @@
.align 2
.globl _start
.extern main_x
.extern _global_pointer

.set mtvt, 0x307
.set msip, 0x20000000
Expand All @@ -56,6 +57,9 @@ _start:
csrs mstatus, t0
fscsr x0

/* Set/enable the global pointer for small ram */
la gp, _global_pointer

/* Read machine hart ID */
csrr a0, mhartid
bnez a0, .L_core1
Expand Down
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