[mid-end][__RTL] Clean state despite invalid __RTL startwith passes

Hi there,

When compiling an __RTL function that has an invalid "startwith" pass we
currently don't run the dfinish cleanup pass. This means we ICE on the next
function.

This change ensures that all state is cleaned up for the next function
to run correctly.

As an example, before this change the following code would ICE when compiling
the function `foo2` because the "peephole2" pass is not run at optimisation
level -O0.

When compiled with
./aarch64-none-linux-gnu-gcc -O0 -S missed-pass-error.c -o test.s

```
int __RTL (startwith ("peephole2")) badfoo ()
{
(function "badfoo"
  (insn-chain
    (block 2
      (edge-from entry (flags "FALLTHRU"))
      (cnote 3 [bb 2] NOTE_INSN_BASIC_BLOCK)
      (cinsn 101 (set (reg:DI x19) (reg:DI x0)))
      (cinsn 10 (use (reg/i:SI x19)))
      (edge-to exit (flags "FALLTHRU"))
    ) ;; block 2
  ) ;; insn-chain
) ;; function "foo2"
}

int __RTL (startwith ("final")) foo2 ()
{
(function "foo2"
  (insn-chain
    (block 2
      (edge-from entry (flags "FALLTHRU"))
      (cnote 3 [bb 2] NOTE_INSN_BASIC_BLOCK)
      (cinsn 101 (set (reg:DI x19) (reg:DI x0)))
      (cinsn 10 (use (reg/i:SI x19)))
      (edge-to exit (flags "FALLTHRU"))
    ) ;; block 2
  ) ;; insn-chain
) ;; function "foo2"
}
```

Now it silently ignores the __RTL function and successfully compiles foo2.

regtest done on aarch64
regtest done on x86_64

OK for trunk?

gcc/ChangeLog:

2019-11-15  Matthew Malcomson  <matthew.malcomson@arm.com>

	* passes.c (should_skip_pass_p): Always run "dfinish".

gcc/testsuite/ChangeLog:

2019-11-15  Matthew Malcomson  <matthew.malcomson@arm.com>

	* gcc.dg/rtl/aarch64/missed-pass-error.c: New test.

From-SVN: r278283

4 files changed, 55 insertions, 1 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index dbc85d5d..8db3c4ad 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2019-11-15  Matthew Malcomson  <matthew.malcomson@arm.com>
+
+	* passes.c (should_skip_pass_p): Always run "dfinish".
+
 2019-11-15  Richard Biener  <rguenther@suse.de>
 
 	* ipa-inline.c (inline_small_functions): Move assignment
diff --git a/gcc/passes.c b/gcc/passes.c
index cfc0fef..b77356d 100644
--- a/gcc/passes.c
+++ b/gcc/passes.c
@@ -2375,7 +2375,8 @@ should_skip_pass_p (opt_pass *pass)
     return false;
 
   /* Don't skip df init; later RTL passes need it.  */
-  if (strstr (pass->name, "dfinit") != NULL)
+  if (strstr (pass->name, "dfinit") != NULL
+      || strstr (pass->name, "dfinish") != NULL)
     return false;
 
   if (!quiet_flag)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index e537e5d..2b630ef 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2019-11-15  Matthew Malcomson  <matthew.malcomson@arm.com>
+
+	* gcc.dg/rtl/aarch64/missed-pass-error.c: New test.
+
 2019-11-15  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/92039
diff --git a/gcc/testsuite/gcc.dg/rtl/aarch64/missed-pass-error.c b/gcc/testsuite/gcc.dg/rtl/aarch64/missed-pass-error.c
new file mode 100644
index 0000000..2f02ca9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/rtl/aarch64/missed-pass-error.c
@@ -0,0 +1,45 @@
+/* { dg-do compile { target aarch64-*-* } } */
+/* { dg-additional-options "-O0" } */
+
+/*
+   When compiling __RTL functions the startwith string can be either incorrect
+   (i.e. not matching a pass) or be unused (i.e. can refer to a pass that is
+   not run at the current optimisation level).
+
+   Here we ensure that the state clean up is still run, so that functions other
+   than the faulty one can still be compiled.
+ */
+
+int __RTL (startwith ("peephole2")) badfoo ()
+{
+(function "badfoo"
+  (insn-chain
+    (block 2
+      (edge-from entry (flags "FALLTHRU"))
+      (cnote 3 [bb 2] NOTE_INSN_BASIC_BLOCK)
+      (cinsn 101 (set (reg:DI x19) (reg:DI x0)))
+      (cinsn 10 (use (reg/i:SI x19)))
+      (edge-to exit (flags "FALLTHRU"))
+    ) ;; block 2
+  ) ;; insn-chain
+) ;; function "foo2"
+}
+
+/* Compile a valid __RTL function to test state from the "dfinit" pass has been
+   cleaned with the "dfinish" pass.  */
+
+int __RTL (startwith ("final")) foo2 ()
+{
+(function "foo2"
+  (insn-chain
+    (block 2
+      (edge-from entry (flags "FALLTHRU"))
+      (cnote 3 [bb 2] NOTE_INSN_BASIC_BLOCK)
+      (cinsn 101 (set (reg:DI x19) (reg:DI x0)))
+      (cinsn 10 (use (reg/i:SI x19)))
+      (edge-to exit (flags "FALLTHRU"))
+    ) ;; block 2
+  ) ;; insn-chain
+) ;; function "foo2"
+}
+