[PATCH][ARM] PR target/68648: Fold NOT of CONST_INT in andsi_iorsi3_notsi splitter

[Kyrill Tkachov]

Hi all,

In this PR we ICE because during post-reload splitting we generate the insn:
(insn 27 26 11 2 (set (reg:SI 0 r0 [orig:121 D.4992 ] [121])
        (and:SI (not:SI (const_int 1 [0x1]))
            (reg:SI 0 r0 [orig:121 D.4992 ] [121])))
     (nil))


The splitter at fault is andsi_iorsi3_notsi that accepts a const_int in 
operands[3]
and outputs (not (match_dup 3)). It should really be trying to constant fold 
the result
first.  This patch does that by calling simplify_gen_unary to generate the 
complement
of operands[3] if it's a register or the appropriate const_int rtx with the 
correct
folded result that will still properly match the arm bic-immediate instruction.

Bootstrapped and tested on arm-none-eabi.

Is this ok for trunk?

This appears on GCC 4.9 and GCC 5 and I'll be testing the fix there as well.
Ok for those branches if testing is successful?

Thanks,
Kyrill

2015-12-07  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    PR target/68648
    * config/arm/arm.md (*andsi_iorsi3_notsi): Try to simplify
    the complement of operands[3] during splitting.

2015-12-07  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    PR target/68648
    * gcc.c-torture/execute/pr68648.c: New test.

diff --git a/gcc/config/arm/arm.md b/gcc/config/arm/arm.md
index 2b48bbaf034b286d723536ec2aa6fe0f9b312911..dfb75c5f11c66c6b4a34ff3071b5a0957c3512cb 100644
--- a/gcc/config/arm/arm.md
+++ b/gcc/config/arm/arm.md
@@ -3274,8 +3274,22 @@ (define_insn_and_split "*andsi_iorsi3_notsi"
   "#"   ; "orr%?\\t%0, %1, %2\;bic%?\\t%0, %0, %3"
   "&& reload_completed"
   [(set (match_dup 0) (ior:SI (match_dup 1) (match_dup 2)))
-   (set (match_dup 0) (and:SI (not:SI (match_dup 3)) (match_dup 0)))]
-  ""
+   (set (match_dup 0) (and:SI (match_dup 4) (match_dup 5)))]
+  {
+     /* If operands[3] is a constant make sure to fold the NOT into it
+	to avoid creating a NOT of a CONST_INT.  */
+    rtx not_rtx = simplify_gen_unary (NOT, SImode, operands[3], SImode);
+    if (CONST_INT_P (not_rtx))
+      {
+	operands[4] = operands[0];
+	operands[5] = not_rtx;
+      }
+    else
+      {
+	operands[5] = operands[0];
+	operands[4] = not_rtx;
+      }
+  }
   [(set_attr "length" "8")
    (set_attr "ce_count" "2")
    (set_attr "predicable" "yes")
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr68648.c b/gcc/testsuite/gcc.c-torture/execute/pr68648.c
new file mode 100644
index 0000000000000000000000000000000000000000..fc66806a99a0abef7bd517ae2f5200b387e69ce4
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr68648.c
@@ -0,0 +1,20 @@
+int __attribute__ ((noinline))
+foo (void)
+{
+  return 123;
+}
+
+int __attribute__ ((noinline))
+bar (void)
+{
+  int c = 1;
+  c |= 4294967295 ^ (foo () | 4073709551608);
+  return c;
+}
+
+int
+main ()
+{
+  if (bar () != 0x83fd4005)
+    __builtin_abort ();
+}