rp2: Switch to locally provided math library.

This commit fixes all known floating-point bugs with the pico-sdk.  There
are two things going on here:
- Use a custom pico float component so that the pico-sdk doesn't include
  its math functions, and then provide our own from lib/libm.
- Provide a wrapper for __aeabi_fadd to fix the infinity addition bug.

Prior to this commit, the following tests failed on the rp2 port: cmath_fun
float_parse math_domain math_domain_special math_fun_special.  With this
commit, all these tests pass.

Thanks to @projectgus for how to approach this fix.

Signed-off-by: Damien George <damien@micropython.org>

ports/rp2/CMakeLists.txt

@@ -196,6 +196,73 @@ set(PICO_SDK_COMPONENTS
     tinyusb_device
 )
 
+# Use our custom pico_float_micropython float implementation.  This is needed for two reasons:
+# - to fix inf handling in pico-sdk's __wrap___aeabi_fadd();
+# - so we can use our own libm functions, to fix inaccuracies in the pico-sdk versions.
+pico_set_float_implementation(${MICROPY_TARGET} micropython)
+
+# Define our custom pico_float_micropython component.
+pico_add_library(pico_float_micropython)
+
+# pico_float_micropython: add pico-sdk float and our libm source files.
+target_sources(pico_float_micropython INTERFACE
+    ${PICO_SDK_PATH}/src/rp2_common/pico_float/float_aeabi.S
+    ${PICO_SDK_PATH}/src/rp2_common/pico_float/float_init_rom.c
+    ${PICO_SDK_PATH}/src/rp2_common/pico_float/float_v1_rom_shim.S
+    ${MICROPY_DIR}/lib/libm/math.c
+    ${MICROPY_DIR}/lib/libm/acoshf.c
+    ${MICROPY_DIR}/lib/libm/asinfacosf.c
+    ${MICROPY_DIR}/lib/libm/asinhf.c
+    ${MICROPY_DIR}/lib/libm/atan2f.c
+    ${MICROPY_DIR}/lib/libm/atanf.c
+    ${MICROPY_DIR}/lib/libm/atanhf.c
+    ${MICROPY_DIR}/lib/libm/ef_rem_pio2.c
+    ${MICROPY_DIR}/lib/libm/ef_sqrt.c
+    ${MICROPY_DIR}/lib/libm/erf_lgamma.c
+    ${MICROPY_DIR}/lib/libm/fmodf.c
+    ${MICROPY_DIR}/lib/libm/kf_cos.c
+    ${MICROPY_DIR}/lib/libm/kf_rem_pio2.c
+    ${MICROPY_DIR}/lib/libm/kf_sin.c
+    ${MICROPY_DIR}/lib/libm/kf_tan.c
+    ${MICROPY_DIR}/lib/libm/log1pf.c
+    ${MICROPY_DIR}/lib/libm/nearbyintf.c
+    ${MICROPY_DIR}/lib/libm/roundf.c
+    ${MICROPY_DIR}/lib/libm/sf_cos.c
+    ${MICROPY_DIR}/lib/libm/sf_erf.c
+    ${MICROPY_DIR}/lib/libm/sf_frexp.c
+    ${MICROPY_DIR}/lib/libm/sf_ldexp.c
+    ${MICROPY_DIR}/lib/libm/sf_modf.c
+    ${MICROPY_DIR}/lib/libm/sf_sin.c
+    ${MICROPY_DIR}/lib/libm/sf_tan.c
+    ${MICROPY_DIR}/lib/libm/wf_lgamma.c
+    ${MICROPY_DIR}/lib/libm/wf_tgamma.c
+    ${MICROPY_PORT_DIR}/libm_extra.c
+)
+
+# pico_float_micropython: wrap low-level floating-point ops, to call the pico-sdk versions.
+pico_wrap_function(pico_float_micropython __aeabi_fdiv)
+pico_wrap_function(pico_float_micropython __aeabi_fmul)
+pico_wrap_function(pico_float_micropython __aeabi_frsub)
+pico_wrap_function(pico_float_micropython __aeabi_fsub)
+pico_wrap_function(pico_float_micropython __aeabi_cfcmpeq)
+pico_wrap_function(pico_float_micropython __aeabi_cfrcmple)
+pico_wrap_function(pico_float_micropython __aeabi_cfcmple)
+pico_wrap_function(pico_float_micropython __aeabi_fcmpeq)
+pico_wrap_function(pico_float_micropython __aeabi_fcmplt)
+pico_wrap_function(pico_float_micropython __aeabi_fcmple)
+pico_wrap_function(pico_float_micropython __aeabi_fcmpge)
+pico_wrap_function(pico_float_micropython __aeabi_fcmpgt)
+pico_wrap_function(pico_float_micropython __aeabi_fcmpun)
+pico_wrap_function(pico_float_micropython __aeabi_i2f)
+pico_wrap_function(pico_float_micropython __aeabi_l2f)
+pico_wrap_function(pico_float_micropython __aeabi_ui2f)
+pico_wrap_function(pico_float_micropython __aeabi_ul2f)
+pico_wrap_function(pico_float_micropython __aeabi_f2iz)
+pico_wrap_function(pico_float_micropython __aeabi_f2lz)
+pico_wrap_function(pico_float_micropython __aeabi_f2uiz)
+pico_wrap_function(pico_float_micropython __aeabi_f2ulz)
+pico_wrap_function(pico_float_micropython __aeabi_f2d)
+
 if (MICROPY_PY_LWIP)
     target_link_libraries(${MICROPY_TARGET} micropy_lib_lwip)
 

ports/rp2/libm_extra.c

@@ -0,0 +1,69 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2023 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <math.h>
+#include <stdint.h>
+
+#define INF_POS (0x7f800000)
+#define INF_NEG (0xff800000)
+
+union float_int_t {
+    float f;
+    uint32_t i;
+};
+
+float __wrap___aeabi_fadd(float x, float y);
+
+// The pico-sdk wraps __aeabi_fadd() with __wrap___aeabi_fadd() in order to use the ROM
+// floating-point functions.  But __wrap___aeabi_fadd() does not handle inf+(-inf) or
+// (-inf)+inf correctly.  To fix this we provide our own __aeabi_fadd() that fixes the
+// inf calculation, and do not use the "--wrap=" linker command.  The compiler then
+// picks our __aeabi_fadd() instead of its built-in one.  And the pico-sdk function
+// still exists for us to call.
+float __aeabi_fadd(float x, float y) {
+    // Handle addition of inf/-inf.  This is optimised to reduce C stack usage, and
+    // only have one comparison/jump in the common case of x != inf.
+    union float_int_t xu = {.f = x};
+    union float_int_t yu = {.f = y};
+    if ((xu.i << 1) == (INF_POS << 1)) {
+        if (xu.i == INF_POS) {
+            if (yu.i == INF_POS) {
+                return INFINITY;
+            } else if (yu.i == INF_NEG) {
+                return NAN;
+            }
+        } else {
+            if (yu.i == INF_POS) {
+                return NAN;
+            } else if (yu.i == INF_NEG) {
+                return -INFINITY;
+            }
+        }
+    }
+
+    // Use the pico-sdk function for all other calculations.
+    return __wrap___aeabi_fadd(x, y);
+}