[gcc r16-7848] testsuite: Fix up vec-cvt-1.c for excess precision target [PR124288]

[Jakub Jelinek]

https://gcc.gnu.org/g:fd0f08443955410179d1b06c80bc5a3331d2916d

commit r16-7848-gfd0f08443955410179d1b06c80bc5a3331d2916d
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Mon Mar 2 15:44:40 2026 +0100

    testsuite: Fix up vec-cvt-1.c for excess precision target [PR124288]
    
    The intent of the code is to find the largest (or smallest) representable
    float (or double) smaller (or greater than) or equal to the given integral
    maximum (or minimum).
    The code uses volatile vars to avoid excess precision, but was relying on
    (volatile_var1 = something1 - something2) == volatile_var2
    to actually store the subtraction into volatile var and read it from there,
    making it an optimization barrier.  That is not the case, we compare directly
    the rhs of the assignment expression with volatile_var2, so on excess precision
    targets it can result in unwanted optimizations.
    
    Fixed by using a comma expression to make sure comparison doesn't know the
    value to compare.
    
    2026-03-02  Jakub Jelinek  <jakub@redhat.com>
    
            PR tree-optimization/124288
            * gcc.dg/torture/vec-cvt-1.c (FLTTEST): Use comma expression
            to store into {flt,dbl}m{in,ax} and read from it again for
            comparison.

Diff:
---
 gcc/testsuite/gcc.dg/torture/vec-cvt-1.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/torture/vec-cvt-1.c b/gcc/testsuite/gcc.dg/torture/vec-cvt-1.c
index 78a900956052..0f98c14b6831 100644
--- a/gcc/testsuite/gcc.dg/torture/vec-cvt-1.c
+++ b/gcc/testsuite/gcc.dg/torture/vec-cvt-1.c
@@ -55,22 +55,22 @@ flttointtest##intt (void)						\
   else									\
     {									\
       vf2 = fltmin = min - 1.0f;					\
-      for (vf = 1.0f; (fltmin = vf2 + vf) == vf2; vf = vf * 2.0f)	\
+      for (vf = 1.0f; fltmin = vf2 + vf, fltmin == vf2; vf = vf * 2.0f)	\
 	;								\
     }									\
   vf2 = fltmax = max + 1.0f;						\
-  for (vf = 1.0f; (fltmax = vf2 - vf) == vf2; vf = vf * 2.0f)		\
+  for (vf = 1.0f; fltmax = vf2 - vf, fltmax == vf2; vf = vf * 2.0f)	\
     ;									\
   if (min == 0)								\
     dblmin = 0.0;							\
   else									\
     {									\
       vd2 = dblmin = min - 1.0;						\
-      for (vd = 1.0; (dblmin = vd2 + vd) == vd2; vd = vd * 2.0)		\
+      for (vd = 1.0; dblmin = vd2 + vd, dblmin == vd2; vd = vd * 2.0)	\
 	;								\
     }									\
   vd2 = dblmax = max + 1.0;						\
-  for (vd = 1.0; (dblmax = vd2 - vd) == vd2; vd = vd * 2.0)		\
+  for (vd = 1.0; dblmax = vd2 - vd, dblmax == vd2; vd = vd * 2.0)	\
     ;									\
   for (i = 0; i < N; i++)						\
     {									\