(nuttx) branch master updated: libs/libm: support 128-bit quad-precision and universal fallback in truncl

[acassis]

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acassis pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/nuttx.git


The following commit(s) were added to refs/heads/master by this push:
     new 3c9b6318a00 libs/libm: support 128-bit quad-precision and universal 
fallback in truncl
3c9b6318a00 is described below

commit 3c9b6318a00bef0a7dac4577e0125e9bc3ab8404
Author: Swatantra Yadav <maverickswatan...@gmail.com>
AuthorDate: Thu Oct 15 17:49:55 2026 +0530

    libs/libm: support 128-bit quad-precision and universal fallback in truncl
    
    Previously, truncl() aborted the kernel with PANIC() on architectures where
    long double is not equal to double and LDBL_MANT_DIG != 64 (such as IEEE-754
    binary128 quad-precision on RISC-V 64, AArch64, or SPARC with LDBL_MANT_DIG 
== 113).
    
    This commit:
    1. Extends the musl bit-level branch to support LDBL_MANT_DIG == 113 
(IEEE-754
       quad-precision binary128) with proper big- and little-endian ldshape 
layouts.
    2. Replaces PANIC() in the #else block with an IEEE-754 compliant 
mathematical
       fallback using copysignl((x >= 0.0) ? floorl(x) : ceill(x), x), 
guaranteeing
       that truncl() never crashes on any architecture.
    3. Removes the unused assert.h include and adds endian.h in alphabetical 
order.
    
    Fixes: #18351
    Signed-off-by: Swatantra Yadav <maverickswatan...@gmail.com>
---
 libs/libm/libm/lib_truncl.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/libs/libm/libm/lib_truncl.c b/libs/libm/libm/lib_truncl.c
index 48aabbba872..91c8c80ac2d 100644
--- a/libs/libm/libm/lib_truncl.c
+++ b/libs/libm/libm/lib_truncl.c
@@ -35,10 +35,10 @@
 #include <nuttx/config.h>
 #include <nuttx/compiler.h>
 
-#include <assert.h>
-#include <stdint.h>
+#include <endian.h>
 #include <float.h>
 #include <math.h>
+#include <stdint.h>
 
 /****************************************************************************
  * Public Functions
@@ -54,7 +54,7 @@ long double truncl(long double x)
   return trunc(x);
 }
 
-#elif LDBL_MANT_DIG == 64
+#elif LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113
 
 static const long double toint = 1 / LDBL_EPSILON;
 
@@ -63,8 +63,21 @@ union ldshape
   long double f;
   struct
     {
+#if LDBL_MANT_DIG == 64
       uint64_t m;
       uint16_t se;
+#elif defined(CONFIG_ENDIAN_BIG) || \
+      (defined(__BYTE_ORDER__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
+      uint16_t se;
+      uint16_t top;
+      uint32_t mid;
+      uint64_t lo;
+#else
+      uint64_t lo;
+      uint32_t mid;
+      uint16_t top;
+      uint16_t se;
+#endif
     } i;
 };
 
@@ -113,9 +126,16 @@ long double truncl(long double x)
 
 #else
 
+/* Universal fallback for any other long double representation */
+
 long double truncl(long double x)
 {
-  PANIC();  /* FIX ME */
+  if (isnan(x))
+    {
+      return x;
+    }
+
+  return copysignl((x >= 0.0) ? floorl(x) : ceill(x), x);
 }
 
 #endif