Remove no-op register to register copies in CSE just like we remove no-op memory...

        PR rtl-optimization/90275
        * cse.c (cse_insn): Delete no-op register moves too.

        PR rtl-optimization/90275
        * gcc.c-torture/compile/pr90275.c: New test.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index b184a1af8e98577883fb8eadcf6a3ff415a9a837..f1a1984e8c744d940ef106b565c00ed58d6f8c12 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2020-03-12  Richard Sandiford  <richard.sandiford@arm.com>
+
+       PR rtl-optimization/90275
+       * cse.c (cse_insn): Delete no-op register moves too.
+
 2020-03-12  Darius Galis  <darius.galis@cyberthorstudios.com>
 
        * config/rx/rx.md (CTRLREG_CPEN): Remove.

diff --git a/gcc/cse.c b/gcc/cse.c
index 79ee0ce80e3dd68a450cb2f493f79b19f098f4fa..08984c170403e00929785ee067d6668d52731721 100644 (file)
--- a/gcc/cse.c
+++ b/gcc/cse.c
@@ -4625,7 +4625,7 @@ cse_insn (rtx_insn *insn)
   for (i = 0; i < n_sets; i++)
     {
       bool repeat = false;
-      bool mem_noop_insn = false;
+      bool noop_insn = false;
       rtx src, dest;
       rtx src_folded;
       struct table_elt *elt = 0, *p;
@@ -5324,9 +5324,11 @@ cse_insn (rtx_insn *insn)
            }
 
          /* Similarly, lots of targets don't allow no-op
-            (set (mem x) (mem x)) moves.  */
+            (set (mem x) (mem x)) moves.  Even (set (reg x) (reg x))
+            might be impossible for certain registers (like CC registers).  */
          else if (n_sets == 1
-                  && MEM_P (trial)
+                  && !CALL_P (insn)
+                  && (MEM_P (trial) || REG_P (trial))
                   && MEM_P (dest)
                   && rtx_equal_p (trial, dest)
                   && !side_effects_p (dest)
@@ -5334,7 +5336,7 @@ cse_insn (rtx_insn *insn)
                       || insn_nothrow_p (insn)))
            {
              SET_SRC (sets[i].rtl) = trial;
-             mem_noop_insn = true;
+             noop_insn = true;
              break;
            }
 
@@ -5562,8 +5564,8 @@ cse_insn (rtx_insn *insn)
          sets[i].rtl = 0;
        }
 
-      /* Similarly for no-op MEM moves.  */
-      else if (mem_noop_insn)
+      /* Similarly for no-op moves.  */
+      else if (noop_insn)
        {
          if (cfun->can_throw_non_call_exceptions && can_throw_internal (insn))
            cse_cfg_altered = true;

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index a5730ebbbc07052e180b14067c529256707b6dda..6d8eac22c313984f105ad0d5d9146cf6ec22f2af 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-03-12  Jeff Law  <law@redhat.com>
+
+       PR rtl-optimization/90275
+       * gcc.c-torture/compile/pr90275.c: New test.
+
 2020-03-12  Richard Biener  <rguenther@suse.de>
 
        PR tree-optimization/94103

diff --git a/gcc/testsuite/gcc.c-torture/compile/pr90275.c b/gcc/testsuite/gcc.c-torture/compile/pr90275.c
new file mode 100644 (file)
index 0000000..83e0df7
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/compile/pr90275.c
@@ -0,0 +1,27 @@
+a, b, c;
+
+long long d;
+
+e() {
+
+  char f;
+
+  for (;;) {
+
+    c = a = c ? 5 : 0;
+
+    if (f) {
+
+      b = a;
+
+      f = d;
+
+    }
+
+    (d || b) < (a > e) ?: (b ? 0 : f) || (d -= f);
+
+  }
+
+}
+
+