gcc/testsuite/gcc.target/nvptx/unsigned-cmp.c

   1 /* { dg-options "-O2" } */
   2 /* { dg-do run } */
   3
   4 /* nvptx backend used to emit lo/ls/hs/hi suffixes on unsigned comparison
   5    insns instead of the more common lt/le/ge/gt, but ptxas and PTX JIT
   6    miscompile 'ls' and 'hi' under some circumstances, such as when the first
   7    source operand expands to a constant memory load, as demonstrated below.
   8    Reported as NVIDIA bug ID 1725195 (tracker is not public).  */
   9
  10 /* Define this to observe PTX translation breakage.  */
  11 //#define EMIT_BROKEN_ASM 1
  12
  13 /* Or define this to get expected codegen.  */
  14 //#define EMIT_WORKING_ASM 1
  15
  16 static __attribute__((noinline,noclone)) int ls(unsigned a)
  17 {
  18     unsigned v;
  19     /* %nctaid.x is always 1 in gcc testing.  */
  20     asm ("mov.u32 %0, %%nctaid.x;" : "=r"(v));
  21 #if defined(EMIT_BROKEN_ASM)
  22     asm ("set.u32.ls.u32 %0, %1, %0;" : "+r"(a) : "r"(v));
  23 #elif defined(EMIT_WORKING_ASM)
  24     asm ("set.u32.le.u32 %0, %1, %0;" : "+r"(a) : "r"(v));
  25 #else
  26     a = v <= a ? -1 : 0;
  27 #endif
  28     return a;
  29 }
  30 static __attribute__((noinline,noclone)) int hi(unsigned a)
  31 {
  32     unsigned v;
  33     asm ("mov.u32 %0, %%nctaid.x;" : "=r"(v));
  34 #if defined(EMIT_BROKEN_ASM)
  35     asm ("set.u32.hi.u32 %0, %1, %0;" : "+r"(a) : "r"(v));
  36 #elif defined(EMIT_WORKING_ASM)
  37     asm ("set.u32.gt.u32 %0, %1, %0;" : "+r"(a) : "r"(v));
  38 #else
  39     a = v > a ? -1 : 0;
  40 #endif
  41     return a;
  42 }
  43 int main()
  44 {
  45     int i;
  46     for (i=0; i<3; i++)
  47         if (ls(i) != -(1 <= i) || hi(i) != -(1 > i))
  48             __builtin_abort();
  49     return 0;
  50 }