[OpenMP] Skip extra blank line when parsing /proc/cpuinfo on LoongArch64

[gonglingqin]

Summary

This fixes the following test cases:

• affinity/kmp-affinity.c
• affinity/kmp-hw-subset.c
• affinity/omp-places.c

[SixWeining]

About the title, how about make it more specfic. Like "[OpenMP] Skip extra blank line when parsing /proc/cpuinfo in kmp_affinity.cpp on LoongArch64".

[gonglingqin]

In D139802#3987351, @SixWeining wrote:

About the title, how about make it more specfic. Like "[OpenMP] Skip extra blank line when parsing /proc/cpuinfo in kmp_affinity.cpp on LoongArch64".

Thanks, I will modify the title.

[xen0n]

openmp/runtime/src/kmp_affinity.cpp

2948–2949

"But on LoongArch a blank line exists before ..." so the sentence could be shorter.

Also, as one of the people behind the kernel port, I can tell you we explicitly added the blank line because the "system type" line is unrelated to any of the CPUs; it's kind of global info. Maybe you can try mentioning this design consideration for more context but I feel it's okay to not do so either. It's up to you.

[gonglingqin]

openmp/runtime/src/kmp_affinity.cpp

2948–2949

Thanks! Glad to know the reason for this design, I will update the comments.

[gonglingqin]

Address @xen0n's comments.

[xen0n]

Thank you very much, this now looks good from the LoongArch side.

openmp/runtime/src/kmp_affinity.cpp

#define CHECK_LINE                                                             \
   if (long_line) {                                                             \
     CLEANUP_THREAD_INFO;                                                       \
     *msg_id = kmp_i18n_str_LongLineCpuinfo;                                    \
     return false;                                                              \
   }
       }
       (*line)++;
 
+#if KMP_ARCH_LOONGARCH64
+      // The parsing logic of /proc/cpuinfo in this function highly depends on
+      // the blank lines between each processor info block. But on LoongArch a
+      // blank line exists before the first processor info block (i.e. after the
+      // "system type" line). This blank line was added because the "system
+      // type" line is unrelated to any of the CPUs. We must skip this line so
+      // that the original logic works on LoongArch.
+      if (*buf == '\n' && *line == 2)
+        continue;
+#endif
+
       char s1[] = "processor";
       if (strncmp(buf, s1, sizeof(s1) - 1) == 0) {
         CHECK_LINE;
         char *p = strchr(buf + sizeof(s1) - 1, ':');
         unsigned val;
         if ((p == NULL) || (KMP_SSCANF(p + 1, "%u\n", &val) != 1))
           goto no_val;
         if (threadInfo[num_avail][osIdIndex] != UINT_MAX)