tree-cfg: Move the returns_twice check to be last statement only [PR114301]

When I was checking to making sure that all of the bugs dealing
with the case where gimple_can_duplicate_bb_p would return false was fixed,
I noticed that the code which was checking if a call statement was
returns_twice was checking all call statements rather than just the
last statement. Since calling gimple_call_flags has a small non-zero
overhead due to a few string comparison, removing the uses of it
can have a small performance improvement. In the case of returns_twice
functions calls, will always end the basic-block due to the check in
stmt_can_terminate_bb_p (and others). So checking only the last statement
is a small optimization and will be safe.

Bootstrapped and tested pon x86_64-linux-gnu with no regressions.

	PR tree-optimization/114301
gcc/ChangeLog:

	* tree-cfg.cc (gimple_can_duplicate_bb_p): Check returns_twice
	only on the last call statement rather than all.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index b2d47b720847b1b867aaa85cc3d6a0217cb9af74..7fb7b92966be0e54824079b193d53a92c3fb28c6 100644 (file)
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -6495,6 +6495,13 @@ gimple_can_duplicate_bb_p (const_basic_block bb)
        && gimple_call_internal_p (last)
        && gimple_call_internal_unique_p (last))
       return false;
+
+    /* Prohibit duplication of returns_twice calls, otherwise associated
+       abnormal edges also need to be duplicated properly.
+       return_twice functions will always be the last statement.  */
+    if (is_gimple_call (last)
+       && (gimple_call_flags (last) & ECF_RETURNS_TWICE))
+      return false;
   }
 
   for (gimple_stmt_iterator gsi = gsi_start_bb (CONST_CAST_BB (bb));
@@ -6502,15 +6509,12 @@ gimple_can_duplicate_bb_p (const_basic_block bb)
     {
       gimple *g = gsi_stmt (gsi);
 
-      /* Prohibit duplication of returns_twice calls, otherwise associated
-        abnormal edges also need to be duplicated properly.
-        An IFN_GOMP_SIMT_ENTER_ALLOC/IFN_GOMP_SIMT_EXIT call must be
+      /* An IFN_GOMP_SIMT_ENTER_ALLOC/IFN_GOMP_SIMT_EXIT call must be
         duplicated as part of its group, or not at all.
         The IFN_GOMP_SIMT_VOTE_ANY and IFN_GOMP_SIMT_XCHG_* are part of such a
         group, so the same holds there.  */
       if (is_gimple_call (g)
-         && (gimple_call_flags (g) & ECF_RETURNS_TWICE
-             || gimple_call_internal_p (g, IFN_GOMP_SIMT_ENTER_ALLOC)
+         && (gimple_call_internal_p (g, IFN_GOMP_SIMT_ENTER_ALLOC)
              || gimple_call_internal_p (g, IFN_GOMP_SIMT_EXIT)
              || gimple_call_internal_p (g, IFN_GOMP_SIMT_VOTE_ANY)
              || gimple_call_internal_p (g, IFN_GOMP_SIMT_XCHG_BFLY)