Hi!
These peephole2s assume that when matching insns like:
[(parallel [(set (reg FLAGS_REG) (match_operand 0))
(match_operand 4)])
that operands[4] must be a set of a register with operands[0]
as SET_SRC, but that isn't the case e.g. for:
(insn 9 8 10 2 (parallel [
(set (reg:CCC 17 flags)
(compare:CCC (unspec_volatile:DI [
(mem/v:DI (reg/v/f:DI 5 di [orig:94 p ] [94]) [-1
S8 A64])
(const_int 5 [0x5])
] UNSPECV_XCHG)
(const_int 0 [0])))
(set (zero_extract:DI (mem/v:DI (reg/v/f:DI 5 di [orig:94 p ] [94])
[-1 S8 A64])
(const_int 1 [0x1])
(reg:DI 0 ax [96]))
(const_int 1 [0x1]))
]) "pr86314.C":7 5268 {atomic_bit_test_and_setdi_1}
(expr_list:REG_DEAD (reg/v/f:DI 5 di [orig:94 p ] [94])
(expr_list:REG_DEAD (reg:DI 0 ax [96])
(nil))))
As we want to clear operands[3] before this instruction, we need to
verify that it isn't used in operands[0] (we check that) and that
operands[4] does not set it (also checked), but also need to check that
operands[4] doesn't use it (which we don't do). In the usual case
when SET_DEST of operands[4] is a REG and SET_SRC is operands[0] it
makes no difference, but if SET_DEST sets something that uses operands[3]
in it, or if SET_SRC is different from operands[0] and uses operands[3],
then this results in a wrong peephole2 transformation.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk and release branches?
2018-06-26 Jakub Jelinek <ja...@redhat.com>
PR target/86314
* config/i386/i386.md (setcc + movzbl to xor + setcc peephole2s):
Check reg_overlap_mentioned_p in addition to reg_set_p with the same
operands.
* gcc.dg/pr86314.c: New test.
--- gcc/config/i386/i386.md.jj 2018-06-25 14:51:24.878990827 +0200
+++ gcc/config/i386/i386.md 2018-06-26 10:01:43.042907384 +0200
@@ -12761,6 +12761,7 @@ (define_peephole2
"(peep2_reg_dead_p (3, operands[1])
|| operands_match_p (operands[1], operands[3]))
&& ! reg_overlap_mentioned_p (operands[3], operands[0])
+ && ! reg_overlap_mentioned_p (operands[3], operands[4])
&& ! reg_set_p (operands[3], operands[4])
&& peep2_regno_dead_p (0, FLAGS_REG)"
[(parallel [(set (match_dup 5) (match_dup 0))
@@ -12786,6 +12787,7 @@ (define_peephole2
|| operands_match_p (operands[2], operands[4]))
&& ! reg_overlap_mentioned_p (operands[4], operands[0])
&& ! reg_overlap_mentioned_p (operands[4], operands[1])
+ && ! reg_overlap_mentioned_p (operands[4], operands[5])
&& ! reg_set_p (operands[4], operands[5])
&& refers_to_regno_p (FLAGS_REG, operands[1], (rtx *)NULL)
&& peep2_regno_dead_p (0, FLAGS_REG)"
@@ -12835,6 +12837,7 @@ (define_peephole2
"(peep2_reg_dead_p (3, operands[1])
|| operands_match_p (operands[1], operands[3]))
&& ! reg_overlap_mentioned_p (operands[3], operands[0])
+ && ! reg_overlap_mentioned_p (operands[3], operands[4])
&& ! reg_set_p (operands[3], operands[4])
&& peep2_regno_dead_p (0, FLAGS_REG)"
[(parallel [(set (match_dup 5) (match_dup 0))
@@ -12861,6 +12864,7 @@ (define_peephole2
|| operands_match_p (operands[2], operands[4]))
&& ! reg_overlap_mentioned_p (operands[4], operands[0])
&& ! reg_overlap_mentioned_p (operands[4], operands[1])
+ && ! reg_overlap_mentioned_p (operands[4], operands[5])
&& ! reg_set_p (operands[4], operands[5])
&& refers_to_regno_p (FLAGS_REG, operands[1], (rtx *)NULL)
&& peep2_regno_dead_p (0, FLAGS_REG)"
--- gcc/testsuite/gcc.dg/pr86314.c.jj 2018-06-26 10:25:35.190160477 +0200
+++ gcc/testsuite/gcc.dg/pr86314.c 2018-06-26 10:24:42.310077331 +0200
@@ -0,0 +1,20 @@
+// PR target/86314
+// { dg-do run { target sync_int_long } }
+// { dg-options "-O2" }
+
+__attribute__((noinline, noclone)) unsigned long
+foo (unsigned long *p)
+{
+ unsigned long m = 1UL << ((*p & 1) ? 1 : 0);
+ unsigned long n = __atomic_fetch_or (p, m, __ATOMIC_SEQ_CST);
+ return (n & m) == 0;
+}
+
+int
+main ()
+{
+ unsigned long v = 1;
+ if (foo (&v) != 1)
+ __builtin_abort ();
+ return 0;
+}
Jakub
