[newlib-cygwin/main] Fix rounding results in lrint() & llrint() when close to 0

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=9e329b544ac04b389e12984362e06b92e1506399

commit 9e329b544ac04b389e12984362e06b92e1506399
Author:     Jesse Huang via Newlib <newlib@sourceware.org>
AuthorDate: Thu Jul 27 01:49:41 2023 -0700
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Thu Jul 27 11:14:12 2023 +0200

    Fix rounding results in lrint() & llrint() when close to 0
    
    soft-fp should round floating pointer numbers according to the current
    rounding mode. However, in the current code of lrint() and llrint(),
    there are if statements before the actual rounding computation
    
          if(j0 < -1)
            return 0;
    
    Where j0 is the exponent of the floating point number.
    
    It means any number having a exponent less than -1
    (i.e. interval (-0.5, 0.5)) will be rounded to 0 regardeless of the
    rounding mode.
    
    The bug already fixed in glibc in 2006 by moving the check afterwards
    the rounding computation, but still persists in newlib.
    
    This patch fixed it in a similar way to glibc
    Ref Commit in glibc: 6624dbc07b5a9fb316ed188ef01f65b8eea8b47c

Diff:
---
 newlib/libm/common/s_llrint.c  | 31 +++++++++++--------------------
 newlib/libm/common/s_lrint.c   | 31 +++++++++++--------------------
 newlib/libm/common/sf_llrint.c |  6 ++----
 newlib/libm/common/sf_lrint.c  |  6 ++----
 4 files changed, 26 insertions(+), 48 deletions(-)

diff --git a/newlib/libm/common/s_llrint.c b/newlib/libm/common/s_llrint.c
index 72452dbe9342..f2c48766e47c 100644
--- a/newlib/libm/common/s_llrint.c
+++ b/newlib/libm/common/s_llrint.c
@@ -66,26 +66,17 @@ long long int
   if(j0 < 20)
     {
       /* j0 in [-1023,19] */
-      if(j0 < -1)
-        return 0;
-      else
-        {
-          /* j0 in [0,19] */
-	  /* shift amt in [0,19] */
-          w = TWO52[sx] + x;
-          t = w - TWO52[sx];
-          GET_HIGH_WORD(i0, t);
-          /* Detect the all-zeros representation of plus and
-             minus zero, which fails the calculation below. */
-          if ((i0 & ~((__int32_t)1 << 31)) == 0)
-              return 0;
-          /* After round:  j0 in [0,20] */
-          j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
-          i0 &= 0x000fffff;
-          i0 |= 0x00100000;
-	  /* shift amt in [20,0] */
-          result = i0 >> (20 - j0);
-        }
+      w = TWO52[sx] + x;
+      t = w - TWO52[sx];
+      GET_HIGH_WORD(i0, t);
+      /* Detect the all-zeros representation of plus and
+         minus zero, which fails the calculation below. */
+      if ((i0 & ~((__int32_t)1 << 31)) == 0)
+          return 0;
+      j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
+      i0 &= 0x000fffff;
+      i0 |= 0x00100000;
+      result = (j0 < 0 ? 0 : i0 >> (20 - j0));
     }
   else if (j0 < (int)(8 * sizeof (long long int)) - 1)
     {
diff --git a/newlib/libm/common/s_lrint.c b/newlib/libm/common/s_lrint.c
index b37f50fd4d52..b37b93affa26 100644
--- a/newlib/libm/common/s_lrint.c
+++ b/newlib/libm/common/s_lrint.c
@@ -103,26 +103,17 @@ TWO52[2]={
   if(j0 < 20)
     {
       /* j0 in [-1023,19] */
-      if(j0 < -1)
-        return 0;
-      else
-        {
-          /* j0 in [0,19] */
-	  /* shift amt in [0,19] */
-          w = TWO52[sx] + x;
-          t = w - TWO52[sx];
-          GET_HIGH_WORD(i0, t);
-          /* Detect the all-zeros representation of plus and
-             minus zero, which fails the calculation below. */
-          if ((i0 & ~(1L << 31)) == 0)
-              return 0;
-          /* After round:  j0 in [0,20] */
-          j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
-          i0 &= 0x000fffff;
-          i0 |= 0x00100000;
-	  /* shift amt in [20,0] */
-          result = i0 >> (20 - j0);
-        }
+      w = TWO52[sx] + x;
+      t = w - TWO52[sx];
+      GET_HIGH_WORD(i0, t);
+      /* Detect the all-zeros representation of plus and
+         minus zero, which fails the calculation below. */
+      if ((i0 & ~(1L << 31)) == 0)
+          return 0;
+      j0 = ((i0 & 0x7ff00000) >> 20) - 1023;
+      i0 &= 0x000fffff;
+      i0 |= 0x00100000;
+      result = (j0 < 0 ? 0 : i0 >> (20 - j0));
     }
   else if (j0 < (int)(8 * sizeof (long int)) - 1)
     {
diff --git a/newlib/libm/common/sf_llrint.c b/newlib/libm/common/sf_llrint.c
index 7558e89acd56..905a5b21d040 100644
--- a/newlib/libm/common/sf_llrint.c
+++ b/newlib/libm/common/sf_llrint.c
@@ -60,9 +60,7 @@ TWO23[2]={
   
   if (j0 < (int)(sizeof (long long int) * 8) - 1)
     {
-      if (j0 < -1)
-        return 0;
-      else if (j0 >= 23)
+      if (j0 >= 23)
         result = (long long int) ((i0 & 0x7fffff) | 0x800000) << (j0 - 23);
       else
         {
@@ -76,7 +74,7 @@ TWO23[2]={
           j0 = ((i0 >> 23) & 0xff) - 0x7f;
           i0 &= 0x7fffff;
           i0 |= 0x800000;
-          result = i0 >> (23 - j0);
+          result = (j0 < 0 ? 0 : i0 >> (23 - j0));
         }
     }
   else
diff --git a/newlib/libm/common/sf_lrint.c b/newlib/libm/common/sf_lrint.c
index 3c58c5d10121..7fe47aefb264 100644
--- a/newlib/libm/common/sf_lrint.c
+++ b/newlib/libm/common/sf_lrint.c
@@ -60,9 +60,7 @@ TWO23[2]={
   
   if (j0 < (int)(sizeof (long int) * 8) - 1)
     {
-      if (j0 < -1)
-        return 0;
-      else if (j0 >= 23)
+      if (j0 >= 23)
         result = (long int) ((i0 & 0x7fffff) | 0x800000) << (j0 - 23);
       else
         {
@@ -76,7 +74,7 @@ TWO23[2]={
           j0 = ((i0 >> 23) & 0xff) - 0x7f;
           i0 &= 0x7fffff;
           i0 |= 0x800000;
-          result = i0 >> (23 - j0);
+          result = (j0 < 0 ? 0 : i0 >> (23 - j0));
         }
     }
   else