[PATCH] Fix up CSE handling of const/pure calls (PR rtl-optimization/71532)

[Jakub Jelinek]

Hi!

As the following testcase shows, CSE mishandles const/pure calls, it assumes
that const/pure calls can't clobber even their argument slots.  But, the
argument slots are owned by the callee, so need to be volatile across the
calls.  On the testcase the second round of argument stores is eliminated,
because CSE thinks those memory slots already have the right values.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?

2016-06-15  Jakub Jelinek  <ja...@redhat.com>

        PR rtl-optimization/71532
        * cse.c (cse_insn): For const/pure calls, invalidate argument passing
        memory slots.

        * gcc.dg/torture/pr71532.c: New test.

--- gcc/cse.c.jj        2016-05-20 09:05:08.000000000 +0200
+++ gcc/cse.c   2016-06-15 16:01:21.568523552 +0200
@@ -5751,6 +5751,13 @@ cse_insn (rtx_insn *insn)
     {
       if (!(RTL_CONST_OR_PURE_CALL_P (insn)))
        invalidate_memory ();
+      else
+       /* For const/pure calls, invalidate any argument slots, because
+          those are owned by the callee.  */
+       for (tem = CALL_INSN_FUNCTION_USAGE (insn); tem; tem = XEXP (tem, 1))
+         if (GET_CODE (XEXP (tem, 0)) == USE
+             && MEM_P (XEXP (XEXP (tem, 0), 0)))
+           invalidate (XEXP (XEXP (tem, 0), 0), VOIDmode);
       invalidate_for_call ();
     }
 
--- gcc/testsuite/gcc.dg/torture/pr71532.c.jj   2016-06-15 16:37:55.340368699 
+0200
+++ gcc/testsuite/gcc.dg/torture/pr71532.c      2016-06-15 16:39:45.841956435 
+0200
@@ -0,0 +1,39 @@
+/* PR rtl-optimization/71532 */
+/* { dg-do run } */
+/* { dg-additional-options "-mtune=slm" { target i?86-*-* x86_64-*-* } } */
+
+__attribute__((noinline, noclone, pure)) int
+foo (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int 
k, int l)
+{
+  a++; b++; c++; d++; e++; f++; g++; h++; i++; j++; k++; l++;
+  asm volatile ("" : : "g" (&a), "g" (&b), "g" (&c), "g" (&d) : "memory");
+  asm volatile ("" : : "g" (&e), "g" (&f), "g" (&g), "g" (&h) : "memory");
+  asm volatile ("" : : "g" (&i), "g" (&j), "g" (&k), "g" (&l) : "memory");
+  return a + b + c + d + e + f + g + h + i + j + k + l;
+}
+
+__attribute__((noinline, noclone, pure)) int
+bar (int a, int b, int c, int d, int e, int f, int g, int h, int i, int j, int 
k, int l)
+{
+  a++; b++; c++; d++; e++; f++; g++; h++; i++; j++; k++; l++;
+  asm volatile ("" : : "g" (&a), "g" (&b), "g" (&c), "g" (&d) : "memory");
+  asm volatile ("" : : "g" (&e), "g" (&f), "g" (&g), "g" (&h) : "memory");
+  asm volatile ("" : : "g" (&i), "g" (&j), "g" (&k), "g" (&l) : "memory");
+  return 2 * a + b + c + d + e + f + g + h + i + j + k + l;
+}
+
+__attribute__((noinline, noclone)) int
+test ()
+{
+  int a = foo (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12);
+  a += bar (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12);
+  return a;
+}
+
+int
+main ()
+{
+  if (test () != 182)
+    __builtin_abort ();
+  return 0;
+}

        Jakub