[PATCH] Fix TARGET_READ_MODIFY_WRITE peephole2s (PR target/57568)

[Jakub Jelinek]

Hi!

These two peephole2s misbehave if it sees e.g.
regN = mem
regN = regN + regN
mem = regN
CC = regN != 0
because transforming it into
mem = mem + regN ; CC = mem != 0
is wrong, I forgot to verify the second operand of the
plusminuslogic_operator doesn't overlap the first operand.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk/4.8 and perhaps also 4.7 (where it is just latent)?

2013-06-09  Jakub Jelinek  <ja...@redhat.com>

        PR target/57568
        * config/i386/i386.md (TARGET_READ_MODIFY_WRITE peepholes): Ensure
        that operands[2] doesn't overlap with operands[0].

        * gcc.c-torture/execute/pr57568.c: New test.

--- gcc/config/i386/i386.md.jj  2013-06-03 19:15:34.000000000 +0200
+++ gcc/config/i386/i386.md     2013-06-08 21:59:43.416954936 +0200
@@ -16591,6 +16591,7 @@ (define_peephole2
   "(TARGET_READ_MODIFY_WRITE || optimize_insn_for_size_p ())
    && peep2_reg_dead_p (4, operands[0])
    && !reg_overlap_mentioned_p (operands[0], operands[1])
+   && !reg_overlap_mentioned_p (operands[0], operands[2])
    && (<MODE>mode != QImode
        || immediate_operand (operands[2], QImode)
        || q_regs_operand (operands[2], QImode))
@@ -16655,6 +16656,7 @@ (define_peephole2
        || immediate_operand (operands[2], SImode)
        || q_regs_operand (operands[2], SImode))
    && !reg_overlap_mentioned_p (operands[0], operands[1])
+   && !reg_overlap_mentioned_p (operands[0], operands[2])
    && ix86_match_ccmode (peep2_next_insn (3),
                         (GET_CODE (operands[3]) == PLUS
                          || GET_CODE (operands[3]) == MINUS)
--- gcc/testsuite/gcc.c-torture/execute/pr57568.c.jj    2013-06-08 
22:03:38.861005658 +0200
+++ gcc/testsuite/gcc.c-torture/execute/pr57568.c       2013-06-08 
22:03:19.000000000 +0200
@@ -0,0 +1,12 @@
+/* PR target/57568 */
+
+extern void abort (void);
+int a[6][9] = { }, b = 1, *c = &a[3][5];
+
+int
+main ()
+{
+  if (b && (*c = *c + *c))
+    abort ();
+  return 0;
+}

        Jakub