testsuite: Introduce dg-ice.

This patch adds a new DejaGNU directive, dg-ice, as outlined in the
proposal here:
https://gcc.gnu.org/pipermail/gcc-patches/2020-July/550913.html

It means that it's expected that the compiler crashes with an internal
compiler error when compiling test with such a directive.

A minor optimization could be to use -pass-exit-codes and then check for
ICE_EXIT_CODE return code instead of using string match.

gcc/ChangeLog:

	* doc/sourcebuild.texi: Document dg-ice.

gcc/testsuite/ChangeLog:

	* lib/gcc-dg.exp (gcc-dg-test-1): Handle dg-ice.
	(cleanup-after-saved-dg-test): Reset expect_ice.
	* lib/prune.exp (prune_ices): New.
	* lib/target-supports-dg.exp (dg-ice): New.

3 files changed, 55 insertions, 2 deletions

diff --git a/gcc/testsuite/lib/gcc-dg.exp b/gcc/testsuite/lib/gcc-dg.exp
index 45d97024883..e8ad3052657 100644
--- a/gcc/testsuite/lib/gcc-dg.exp
+++ b/gcc/testsuite/lib/gcc-dg.exp
@@ -308,13 +308,27 @@ proc gcc-dg-test-1 { target_compile prog do_what extra_tool_flags } {
     verbose "$target_compile $prog $output_file $compile_type $options" 4
     set comp_output [$target_compile "$prog" "$output_file" "$compile_type" $options]
 
+    global expect_ice
     # Look for an internal compiler error, which sometimes masks the fact
     # that we didn't get an expected error message.  XFAIL an ICE via
     # dg-xfail-if and use { dg-prune-output ".*internal compiler error.*" }
     # to avoid a second failure for excess errors.
-    if [string match "*internal compiler error*" $comp_output] {
+    # "Error reporting routines re-entered" ICE says "Internal" rather than
+    # "internal", so match that too.
+    if [string match {*[Ii]nternal compiler error*} $comp_output] {
 	upvar 2 name name
-	fail "$name (internal compiler error)"
+	if { $expect_ice == 0 } {
+	  fail "$name (internal compiler error)"
+	} else {
+	  # We expected an ICE and we got it.
+	  xfail "$name (internal compiler error)"
+	  # Prune the ICE from the output.
+	  set comp_output [prune_ices $comp_output]
+	}
+    } elseif { $expect_ice == 1 } {
+	upvar 2 name name
+	# We expected an ICE but we didn't get it.
+	xpass "$name (internal compiler error)"
     }
 
     if { $do_what == "repo" } {
@@ -939,6 +953,7 @@ if { [info procs saved-dg-test] == [list] } {
 	global additional_prunes
 	global compiler_conditional_xfail_data
 	global shouldfail
+	global expect_ice
 	global testname_with_flags
 	global set_target_env_var
 	global set_compiler_env_var
@@ -954,6 +969,7 @@ if { [info procs saved-dg-test] == [list] } {
 	set additional_sources_used ""
 	set additional_prunes ""
 	set shouldfail 0
+	set expect_ice 0
 	if [info exists set_target_env_var] {
 	    unset set_target_env_var
 	}
diff --git a/gcc/testsuite/lib/prune.exp b/gcc/testsuite/lib/prune.exp
index 1c776249f1a..58a739684a5 100644
--- a/gcc/testsuite/lib/prune.exp
+++ b/gcc/testsuite/lib/prune.exp
@@ -118,6 +118,15 @@ proc prune_file_path { text } {
     return $text
 }
 
+# Prune internal compiler error messages, including the "Please submit..."
+# footnote.
+
+proc prune_ices { text } {
+  regsub -all "(^|\n)\[^\n\]*: internal compiler error:.*for instructions\[^\n\]*" $text "" text
+  regsub -all "(^|\n|')*Internal compiler error:.*for instructions\[^\n\]*" $text "" text
+  return $text
+}
+
 # Provide a definition of this if missing (delete after next dejagnu release).
 
 if { [info procs prune_warnings] == "" } then {
diff --git a/gcc/testsuite/lib/target-supports-dg.exp b/gcc/testsuite/lib/target-supports-dg.exp
index 2a21424b890..5bb99f4e8f9 100644
--- a/gcc/testsuite/lib/target-supports-dg.exp
+++ b/gcc/testsuite/lib/target-supports-dg.exp
@@ -495,6 +495,34 @@ proc dg-shouldfail { args } {
     }
 }
 
+# Record whether the compiler is expected (at the moment) to ICE.
+# Used for tests that test bugs that have not been fixed yet.
+
+set expect_ice 0
+
+proc dg-ice { args } {
+    # Don't bother if we're already skipping the test.
+    upvar dg-do-what dg-do-what
+    if { [lindex ${dg-do-what} 1] == "N" } {
+      return
+    }
+
+    global expect_ice
+
+    set args [lreplace $args 0 0]
+    if { [llength $args] > 1 } {
+	set selector [list target [lindex $args 1]]
+	if { [dg-process-target-1 $selector] == "S" } {
+	    # The target matches, now check the flags.
+	    if [check-flags $args] {
+		set expect_ice 1
+	    }
+	}
+    } else {
+	set expect_ice 1
+    }
+}
+
 # Intercept the call to the DejaGnu version of dg-process-target to
 # support use of an effective-target keyword in place of a list of
 # target triplets to xfail or skip a test.