always turn return into __builtin_unreachable for noreturn fuctions [PR119599]

r8-3988-g356fcc67fba52b added code to turn return statements into __builtin_unreachable
calls inside noreturn functions but only while optimizing. Since -funreachable-traps
was added (r13-1204-gd68d3664253696), it is a good idea to move over to using
__builtin_unreachable (and the trap version with this option which defaults at -O0 and -0g)
instead of just a follow through even at -O0.

This also fixes a regression when inlining a noreturn function that returns at -O0 (due to always_inline)
as we would get an empty bb which has no successor edge instead of one with a call to __builtin_unreachable.

I also noticed there was no testcase testing the warning about __builtin_return inside a noreturn function
so I added a testcase there.

Bootstrapped and tested on x86_64-linux-gnu.

	PR ipa/119599

gcc/ChangeLog:

	* tree-cfg.cc (pass_warn_function_return::execute): Turn return statements always
	into __builtin_unreachable calls.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/pr119599-1.c: New test.
	* gcc.dg/builtin-apply5.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>

3 files changed, 61 insertions, 9 deletions

diff --git a/gcc/testsuite/gcc.dg/builtin-apply5.c b/gcc/testsuite/gcc.dg/builtin-apply5.c
new file mode 100644
index 0000000..16892f7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/builtin-apply5.c
@@ -0,0 +1,23 @@
+/* { dg-options "-O2 -Wmissing-noreturn -fgnu89-inline" } */
+/* { dg-additional-options "-mno-mmx" { target { { i?86-*-* x86_64-*-* } && ia32 } } } */
+/* { dg-do compile } */
+
+extern void abort (void);
+
+double
+foo (int arg)
+{
+  if (arg != 116)
+    abort();
+  return arg + 1;
+}
+
+__attribute__((noreturn))
+double
+bar (int arg)
+{
+  foo (arg);
+  __builtin_return (__builtin_apply ((void (*) ()) foo, /* { dg-warning "'noreturn' function does return" } */
+				     __builtin_apply_args (), 16));
+}
+
diff --git a/gcc/testsuite/gcc.dg/torture/pr119599-1.c b/gcc/testsuite/gcc.dg/torture/pr119599-1.c
new file mode 100644
index 0000000..4fbd228
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr119599-1.c
@@ -0,0 +1,27 @@
+/* { dg-do compile } */
+/* { dg-options "-fdump-tree-einline" } */
+
+/* PR ipa/119599 */
+/* inlining a noreturn function which returns
+   can cause an ICE when dealing finding an unreachable block.
+   We should get a __builtin_unreachable after the inliing.  */
+
+
+void baz (void);
+
+static inline __attribute__((always_inline, noreturn)) void
+bar (void)
+{
+  static volatile int t = 0;
+  if (t == 0)
+    baz ();
+} /* { dg-warning "function does return" } */
+
+void
+foo (void)
+{
+  bar ();
+}
+
+/* After inlining, we should have call to __builtin_unreachable now. */
+/* { dg-final { scan-tree-dump "__builtin_unreachable " "einline" } } */
diff --git a/gcc/tree-cfg.cc b/gcc/tree-cfg.cc
index 2fa5678..ecf19d2 100644
--- a/gcc/tree-cfg.cc
+++ b/gcc/tree-cfg.cc
@@ -9799,18 +9799,20 @@ pass_warn_function_return::execute (function *fun)
 	   (e = ei_safe_edge (ei)); )
 	{
 	  last = *gsi_last_bb (e->src);
-	  if ((gimple_code (last) == GIMPLE_RETURN
-	       || gimple_call_builtin_p (last, BUILT_IN_RETURN))
-	      && location == UNKNOWN_LOCATION
-	      && ((location = LOCATION_LOCUS (gimple_location (last)))
-		  != UNKNOWN_LOCATION)
-	      && !optimize)
-	    break;
-	  /* When optimizing, replace return stmts in noreturn functions
+	  /* Warn about __builtin_return .*/
+	  if (gimple_call_builtin_p (last, BUILT_IN_RETURN)
+	      && location == UNKNOWN_LOCATION)
+	    {
+	      location = LOCATION_LOCUS (gimple_location (last));
+	      ei_next (&ei);
+	    }
+	  /* Replace return stmts in noreturn functions
 	     with __builtin_unreachable () call.  */
-	  if (optimize && gimple_code (last) == GIMPLE_RETURN)
+	  else if (gimple_code (last) == GIMPLE_RETURN)
 	    {
 	      location_t loc = gimple_location (last);
+	      if (location == UNKNOWN_LOCATION)
+	        location = LOCATION_LOCUS (loc);
 	      gimple *new_stmt = gimple_build_builtin_unreachable (loc);
 	      gimple_stmt_iterator gsi = gsi_for_stmt (last);
 	      gsi_replace (&gsi, new_stmt, true);