[llvm-bugs] [Bug 42493] New: Passing long double args on 32-bit SPARC violates ABI

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=42493

            Bug ID: 42493
           Summary: Passing long double args on 32-bit SPARC violates ABI
           Product: libraries
           Version: trunk
          Hardware: Sun
                OS: Solaris
            Status: NEW
          Keywords: ABI, miscompilation
          Severity: normal
          Priority: P
         Component: Backend: Sparc
          Assignee: unassignedbugs at nondot.org
          Reporter: ro at gcc.gnu.org
                CC: llvm-bugs at lists.llvm.org, venkatra at cs.wisc.edu

I'm current working to fix the remaining compiler-rt testsuite bugs on SPARC
(https://reviews.llvm.org/D40900).  One of the failures is

    Builtins-sparc-sunos :: divtc3_test.c
    Builtins-sparcv9-sunos :: divtc3_test.c

While the sparcv9 failure is different, the sparc one boils down to incorrectly
passing long double arguments.  Consider the following testcase:

$ cat caller.c
extern void callee (long double);

int
main (void)
{
  long double ld = 1.0;

  callee (ld);
  return 0;
}
$ cat callee.c
extern void abort (void);

void
callee (long double ld)
{
  if (ld != 1.0)
    abort ();
}
$ clang -m32 -c caller.c -o caller.clang.o
$ clang -m32 -c callee.c -o callee.clang.o
$ gcc -m32 -c caller.c -o caller.gcc.o
$ gcc -m32 -c callee.c -o callee.gcc.o
$ gcc -m32 -o clang-gcc caller.clang.o callee.gcc.o 
$ ./clang-gcc 
Segmentation Fault (core dumped)
$ gcc -m32 -o gcc-clang caller.gcc.o callee.clang.o 
$ ./gcc-clang 
Abort (core dumped)

The SPARC psABI, p.3-15 (Structure, Union, and Quad-Precision Arguments)
requires long double args to be passed by reference, while clang passes
them by value (as is correct for SPARCv9).

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