combine: Don't replace SET_SRC with REG_EQUAL note content if SET_SRC has side-effect...

There were some discussions about whether REG_EQUAL notes are valid on insns with a single
set which contains auto-inc-dec side-effects in the SET_SRC and the majority thinks that
it should be valid.  So, this patch fixes the combiner to punt in that case, because otherwise
the auto-inc-dec side-effects from the SET_SRC are lost.

2020-05-06  Jakub Jelinek  <jakub@redhat.com>

	PR rtl-optimization/94873
	* combine.c (combine_instructions): Don't optimize using REG_EQUAL
	note if SET_SRC (set) has side-effects.

	* gcc.dg/pr94873.c: New test.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 94f3c2590f3c0d91ff1c31fb9144933c13425dbe..8040d0d59af0ed1ab7313f725308026f15fc7f91 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-05-06  Jakub Jelinek  <jakub@redhat.com>
+
+       PR rtl-optimization/94873
+       * combine.c (combine_instructions): Don't optimize using REG_EQUAL
+       note if SET_SRC (set) has side-effects.
+
 2020-05-06  Hongtao Liu  <hongtao.liu@intel.com>
            Wei Xiao  <wei3.xiao@intel.com>
 

diff --git a/gcc/combine.c b/gcc/combine.c
index 4c324f38660807432ce2873cce18d5b398b5d4b3..f69413a34d02ad206019450a4bca58f20f6e0ccb 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -1485,6 +1485,7 @@ combine_instructions (rtx_insn *f, unsigned int nregs)
              if ((set = single_set (temp)) != 0
                  && (note = find_reg_equal_equiv_note (temp)) != 0
                  && (note = XEXP (note, 0), GET_CODE (note)) != EXPR_LIST
+                 && ! side_effects_p (SET_SRC (set))
                  /* Avoid using a register that may already been marked
                     dead by an earlier instruction.  */
                  && ! unmentioned_reg_p (note, SET_SRC (set))

diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f8e9f2dccda2e4ddeabb2513138263699ed702b3..1f01ff0b886034da6fd582d0c5dfc19abfc0c97c 100644 (file)
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-05-06  Jakub Jelinek  <jakub@redhat.com>
+
+       PR rtl-optimization/94873
+       * gcc.dg/pr94873.c: New test.
+
 2020-05-06  Hongtao.liu  <hongtao.liu@intel.com>
            Wei Xiao  <wei3.xiao@intel.com>
 

diff --git a/gcc/testsuite/gcc.dg/pr94873.c b/gcc/testsuite/gcc.dg/pr94873.c
new file mode 100644 (file)
index 0000000..3615217
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr94873.c
@@ -0,0 +1,27 @@
+/* PR rtl-optimization/94873 */
+/* { dg-do run { target int128 } } */
+/* { dg-options "-O -fno-merge-constants -fno-split-wide-types -fno-tree-fre" } */
+
+__attribute__((noipa)) void
+foo (const char *p, int q)
+{
+  if (p[0] != '%' || p[1] != '0' || p[2] != '2' || p[3] != 'x' || p[4] != '\0')
+    __builtin_abort ();
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  if ((unsigned char) q != 0x95)
+    __builtin_abort ();
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+  if ((unsigned char) q != 0)
+    __builtin_abort ();
+#endif
+}
+
+int
+main ()
+{
+  union U { __int128 a; char b[sizeof (__int128)]; };
+  char x = ((union U){ .a = 0xF4409395252B9560ULL}).b[1];
+  for (unsigned i = 0; i < sizeof (x); i++)
+    foo ("%02x", i[(volatile unsigned char *) &x]);
+  return 0;
+}