[PATCH] PR84068: Fix sort order of SCHED_PRESSURE_MODEL

[Wilco Dijkstra]

The comparison order for SCHED_PRESSURE_MODEL is incorrect.  If either
instruction is not in target_bb, the ordering is not well defined.  To fix
this, give all instructions in target_bb the highest priority and sort all
other instructions behind it.  This way instructions in target_bb will be
sorted using the pressure model, and instructions outside it will use
RFS_DEP_COUNT and/or RFS_TIE for their order.

Bootstrap OK on AArch64, OK for commit?

ChangeLog:
2018-01-31  Wilco Dijkstra  <wdijk...@arm.com>

        PR rlt-optimization/84068
        * haifa-sched.c (rank_for_schedule): Fix SCHED_PRESSURE_MODEL sorting.

        PR rlt-optimization/84068
        * gcc.dg/pr84068.c: New test.
--

diff --git a/gcc/haifa-sched.c b/gcc/haifa-sched.c
index 
ebdec46bf04f1ba07e8b70607602a3bc9e7ec7de..2c9dd87426930ee99b2a4c0950cadea96f9553bc
 100644
--- a/gcc/haifa-sched.c
+++ b/gcc/haifa-sched.c
@@ -2783,12 +2783,18 @@ rank_for_schedule (const void *x, const void *y)
     }
 
   /* Prefer instructions that occur earlier in the model schedule.  */
-  if (sched_pressure == SCHED_PRESSURE_MODEL
-      && INSN_BB (tmp) == target_bb && INSN_BB (tmp2) == target_bb)
+  if (sched_pressure == SCHED_PRESSURE_MODEL)
     {
-      diff = model_index (tmp) - model_index (tmp2);
-      gcc_assert (diff != 0);
-      return rfs_result (RFS_PRESSURE_INDEX, diff, tmp, tmp2);
+      if (INSN_BB (tmp) == target_bb && INSN_BB (tmp2) == target_bb)
+       {
+         diff = model_index (tmp) - model_index (tmp2);
+         gcc_assert (diff != 0);
+         return rfs_result (RFS_PRESSURE_INDEX, diff, tmp, tmp2);
+       }
+      else if (INSN_BB (tmp) == target_bb)
+       return rfs_result (RFS_PRESSURE_INDEX, -1, tmp, tmp2);
+      else if (INSN_BB (tmp2) == target_bb)
+       return rfs_result (RFS_PRESSURE_INDEX, 1, tmp, tmp2);
     }
 
   /* Prefer the insn which has more later insns that depend on it.
diff --git a/gcc/testsuite/gcc.dg/pr84068.c b/gcc/testsuite/gcc.dg/pr84068.c
new file mode 100644
index 
0000000000000000000000000000000000000000..13110d84455f20edfc50f09efe4074721bd6a7d0
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr84068.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-sched-critical-path-heuristic 
-fno-sched-rank-heuristic --param=max-sched-extend-regions-iters=5 --param 
sched-pressure-algorithm=2" } */
+
+#ifdef __SIZEOF_INT128__
+typedef __int128 largeint;
+#else
+typedef long long largeint;
+#endif
+
+largeint a;
+int b;
+
+largeint
+foo (char d, short e, int f)
+{
+  b = __builtin_sub_overflow_p (b, 1, (unsigned long)0);
+  return a + f;
+}