re PR target/77326 ([avr] Invalid optimization omits comparison)

gcc/
	PR target/77326
	* config/avr/avr.c (avr_notice_update_cc) [CC_NONE]: If insn
	touches some regs mentioned in cc_status, do CC_STATUS_INIT.
gcc/testsuite/
	PR target/77326
	* gcc.target/avr/torture/pr77326.c: New test.

From-SVN: r240306

gcc/ChangeLog

+2016-09-21  Georg-Johann Lay  <avr@gjlay.de>
+
+	PR target/77326
+	* config/avr/avr.c (avr_notice_update_cc) [CC_NONE]: If insn
+	touches some regs mentioned in cc_status, do CC_STATUS_INIT.
+
 2016-09-21  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/77648

gcc/config/avr/avr.c

@@ -2511,8 +2511,44 @@ avr_notice_update_cc (rtx body ATTRIBUTE_UNUSED, rtx_insn *insn)
       break;
 
     case CC_NONE:
-      /* Insn does not affect CC at all.  */
-      break;
+      /* Insn does not affect CC at all, but it might set some registers
+         that are stored in cc_status.  If such a register is affected by
+         the current insn, for example by means of a SET or a CLOBBER,
+         then we must reset cc_status; cf. PR77326.
+
+         Unfortunately, set_of cannot be used as reg_overlap_mentioned_p
+         will abort on COMPARE (which might be found in cc_status.value1/2).
+         Thus work out the registers set by the insn and regs mentioned
+         in cc_status.value1/2.  */
+
+      if (cc_status.value1
+          || cc_status.value2)
+        {
+          HARD_REG_SET regs_used;
+          HARD_REG_SET regs_set;
+          CLEAR_HARD_REG_SET (regs_used);
+
+          if (cc_status.value1
+              && !CONSTANT_P (cc_status.value1))
+            {
+              find_all_hard_regs (cc_status.value1, &regs_used);
+            }
+
+          if (cc_status.value2
+              && !CONSTANT_P (cc_status.value2))
+            {
+              find_all_hard_regs (cc_status.value2, &regs_used);
+            }
+
+          find_all_hard_reg_sets (insn, &regs_set, false);
+
+          if (hard_reg_set_intersect_p (regs_used, regs_set))
+            {
+              CC_STATUS_INIT;
+            }
+        }
+
+      break; // CC_NONE
 
     case CC_SET_N:
       CC_STATUS_INIT;

gcc/testsuite/ChangeLog

+2016-09-21  Georg-Johann Lay  <avr@gjlay.de>
+
+	PR target/77326
+	* gcc.target/avr/torture/pr77326.c: New test.
+
 2016-09-21  Louis Krupp  <louis.krupp@zoho.com>
 
 	* gfortran.dg/pr68078.f90: Run on x86_64_*_linux* only.

gcc/testsuite/gcc.target/avr/torture/pr77326.c

+/* { dg-do run } */
+/* { dg-options "-Wl,--defsym,test1=0" } */
+
+extern void test1 (void) __attribute__((weak));
+
+__attribute__((noinline,noclone))
+static void va_pseudo (int flag, ...)
+{
+  __asm ("nop":);
+}
+
+__attribute__((noinline,noclone))
+static void func (void)
+{
+  va_pseudo (0, 0, 0, 0);
+
+  if (test1)
+    __builtin_abort ();
+}
+
+int main (void)
+{
+  func();
+  __builtin_exit (0);
+  return 0;
+}