[PATCH][AArch64] Improve SHA1 scheduling

Wilco Dijkstra Wilco.Dijkstra@arm.com
Tue Oct 25 17:08:00 GMT 2016


SHA1H instructions may be scheduled after a SHA1C instruction
that uses the same input register.  However SHA1C updates its input,
so if SHA1H is scheduled after it, it requires an extra move.
Increase the priority of SHA1H to ensure it gets scheduled
earlier, avoiding the move.

Is this something the generic scheduler could do automatically for
instructions with RMW operands?

Passes bootstrap & regress. OK for commit?

ChangeLog:
2016-10-25  Wilco Dijkstra  <wdijkstr@arm.com>

	* config/aarch64/aarch64.c (aarch64_sched_adjust_priority)
	New function.
	(TARGET_SCHED_ADJUST_PRIORITY): Define target hook.
--
diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 9b2f9cb19343828dc39e9950ebbefe941521942a..2b25bd1bdd6f4e7737f8e04c3b3684cdff6c4b80 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -13668,6 +13668,26 @@ aarch64_sched_fusion_priority (rtx_insn *insn, int max_pri,
   return;
 }
 
+/* Implement the TARGET_SCHED_ADJUST_PRIORITY hook.
+   Adjust priority of sha1h instructions so they are scheduled before
+   other SHA1 instructions.  */
+
+static int
+aarch64_sched_adjust_priority (rtx_insn *insn, int priority)
+{
+  rtx x = PATTERN (insn);
+
+  if (GET_CODE (x) == SET)
+    {
+      x = SET_SRC (x);
+
+      if (GET_CODE (x) == UNSPEC && XINT (x, 1) == UNSPEC_SHA1H)
+	return priority + 10;
+    }
+
+  return priority;
+}
+
 /* Given OPERANDS of consecutive load/store, check if we can merge
    them into ldp/stp.  LOAD is true if they are load instructions.
    MODE is the mode of memory operands.  */
@@ -14431,6 +14451,9 @@ aarch64_optab_supported_p (int op, machine_mode mode1, machine_mode,
 #undef TARGET_CAN_USE_DOLOOP_P
 #define TARGET_CAN_USE_DOLOOP_P can_use_doloop_if_innermost
 
+#undef TARGET_SCHED_ADJUST_PRIORITY
+#define TARGET_SCHED_ADJUST_PRIORITY aarch64_sched_adjust_priority
+
 #undef TARGET_SCHED_MACRO_FUSION_P
 #define TARGET_SCHED_MACRO_FUSION_P aarch64_macro_fusion_p
 



More information about the Gcc-patches mailing list