[PATCH] Fix PR 110042: ifcvt regression due to paradoxical subregs

[Andrew Pinski via Gcc-patches]

After r14-1014-gc5df248509b489364c573e8, GCC started to emit
directly a zero_extract for `(t1&0x8)!=0`. This introduced
a small regression where ifcvt would not do the ifconversion
as there is now a paradoxical subreg in the dest which
was being rejected. Since paradoxical subreg set the whole
register, we can treat it as the same as a reg in the two places.

OK? Bootstrapped and tested on x86_64-linux-gnu and aarch64-linux-gnu.

gcc/ChangeLog:

        PR rtl-optimization/110042
        * ifcvt.cc (bbs_ok_for_cmove_arith): Allow paradoxical subregs.
        (bb_valid_for_noce_process_p): Strip the subreg for the SET_DEST.

gcc/testsuite/ChangeLog:

        PR rtl-optimization/110042
        * gcc.target/aarch64/csel_bfx_2.c: New test.
---
 gcc/ifcvt.cc                                  | 14 ++++++----
 gcc/testsuite/gcc.target/aarch64/csel_bfx_2.c | 27 +++++++++++++++++++
 2 files changed, 36 insertions(+), 5 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/aarch64/csel_bfx_2.c

diff --git a/gcc/ifcvt.cc b/gcc/ifcvt.cc
index 868eda93251..0b180b4568f 100644
--- a/gcc/ifcvt.cc
+++ b/gcc/ifcvt.cc
@@ -2022,7 +2022,7 @@ bbs_ok_for_cmove_arith (basic_block bb_a, basic_block 
bb_b, rtx to_rename)
        }
 
       /* Make sure this is a REG and not some instance
-        of ZERO_EXTRACT or SUBREG or other dangerous stuff.
+        of ZERO_EXTRACT or non-paradoxical SUBREG or other dangerous stuff.
         If we have a memory destination then we have a pair of simple
         basic blocks performing an operation of the form [addr] = c ? a : b.
         bb_valid_for_noce_process_p will have ensured that these are
@@ -2030,7 +2030,8 @@ bbs_ok_for_cmove_arith (basic_block bb_a, basic_block 
bb_b, rtx to_rename)
         to be renamed.  Assert that the callers set this up properly.  */
       if (MEM_P (SET_DEST (sset_b)))
        gcc_assert (rtx_equal_p (SET_DEST (sset_b), to_rename));
-      else if (!REG_P (SET_DEST (sset_b)))
+      else if (!REG_P (SET_DEST (sset_b))
+              && !paradoxical_subreg_p (SET_DEST (sset_b)))
        {
          BITMAP_FREE (bba_sets);
          return false;
@@ -3136,14 +3137,17 @@ bb_valid_for_noce_process_p (basic_block test_bb, rtx 
cond,
 
          rtx sset = single_set (insn);
          gcc_assert (sset);
+         rtx dest = SET_DEST (sset);
+         if (SUBREG_P (dest))
+           dest = SUBREG_REG (dest);
 
          if (contains_mem_rtx_p (SET_SRC (sset))
-             || !REG_P (SET_DEST (sset))
-             || reg_overlap_mentioned_p (SET_DEST (sset), cond))
+             || !REG_P (dest)
+             || reg_overlap_mentioned_p (dest, cond))
            goto free_bitmap_and_fail;
 
          potential_cost += pattern_cost (sset, speed_p);
-         bitmap_set_bit (test_bb_temps, REGNO (SET_DEST (sset)));
+         bitmap_set_bit (test_bb_temps, REGNO (dest));
        }
     }
 
diff --git a/gcc/testsuite/gcc.target/aarch64/csel_bfx_2.c 
b/gcc/testsuite/gcc.target/aarch64/csel_bfx_2.c
new file mode 100644
index 00000000000..c3b8a6f45cc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/csel_bfx_2.c
@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+unsigned
+f1(int t, int t1)
+{
+  int tt = 0;
+  if(t)
+    tt = (t1&0x8)!=0;
+  return tt;
+}
+struct f
+{
+  unsigned t:3;
+  unsigned t1:4;
+};
+unsigned
+f2(int t, struct f y)
+{
+  int tt = 0;
+  if(t)
+    tt = y.t1;
+  return tt;
+}
+/* Both f1 and f2 should produce a csel and not a cbz on the argument. */
+/*  { dg-final { scan-assembler-times "csel\t" 2 } } */
+/*  { dg-final { scan-assembler-times "ubfx\t" 2 } } */
+/*  { dg-final { scan-assembler-not "cbz\t" } } */
-- 
2.31.1