tree-optimization/101868 - avoid PRE of trapping mems across calls

This backports a fix for the omission of a check of trapping mems
when hoisting them across calls that might not return.  This was
originally done as part of a fix to handle const functions that throw
properly.

2021-08-17  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/101373
	PR tree-optimization/101868
	* tree-ssa-pre.c (prune_clobbered_mems): Also prune trapping
	references when the BB may not return.

	* gcc.dg/lto/pr101868_0.c: New testcase.
	* gcc.dg/lto/pr101868_1.c: Likewise.
	* gcc.dg/lto/pr101868_2.c: Likewise.
	* gcc.dg/lto/pr101868_3.c: Likewise.

gcc/testsuite/gcc.dg/lto/pr101868_0.c

@@ -0,0 +1,33 @@
+/* { dg-lto-do run } */
+/* { dg-lto-options { "-O2 -fno-strict-aliasing -flto" } } */
+
+typedef unsigned long VALUE;
+
+__attribute__ ((cold))
+void rb_check_type(VALUE, int);
+
+static VALUE
+repro(VALUE dummy, VALUE hash)
+{
+    if (hash == 0) {
+        rb_check_type(hash, 1);
+    }
+    else if (*(long *)hash) {
+        rb_check_type(hash, 1);
+    }
+
+
+    return *(long *)hash;
+}
+
+static VALUE (*that)(VALUE dummy, VALUE hash) = repro;
+
+int
+main(int argc, char **argv)
+{
+        argc--;
+        that(0, argc);
+
+        rb_check_type(argc, argc);
+
+}

gcc/testsuite/gcc.dg/lto/pr101868_1.c

@@ -0,0 +1,23 @@
+typedef unsigned long VALUE;
+
+
+__attribute__ ((noreturn)) void rexc_raise(VALUE mesg);
+
+VALUE rb_donothing(VALUE klass);
+
+static void
+funexpected_type(VALUE x, int xt, int t)
+{
+    rexc_raise(rb_donothing(0));
+}
+
+__attribute__ ((cold))
+void
+rb_check_type(VALUE x, int t)
+{
+    int xt;
+
+    if (x == 0) {
+        funexpected_type(x, xt, t);
+    }
+}

gcc/testsuite/gcc.dg/lto/pr101868_2.c

@@ -0,0 +1,11 @@
+typedef unsigned long VALUE;
+
+static void thing(void) {}
+static void (*ptr)(void) = &thing;
+
+VALUE
+rb_donothing(VALUE klass)
+{
+        ptr();
+        return 0;
+}

gcc/testsuite/gcc.dg/lto/pr101868_3.c

@@ -0,0 +1,8 @@
+typedef unsigned long VALUE;
+
+__attribute__((noreturn))
+void
+rexc_raise(VALUE mesg)
+{
+        __builtin_exit(0);
+}

gcc/tree-ssa-pre.c

@@ -2070,6 +2070,13 @@ prune_clobbered_mems (bitmap_set_t set, basic_block block)
 			  && value_dies_in_block_x (expr, block))))
 		to_remove = i;
 	    }
+	  /* If the REFERENCE may trap make sure the block does not contain
+	     a possible exit point.
+	     ???  This is overly conservative if we translate AVAIL_OUT
+	     as the available expression might be after the exit point.  */
+	  if (BB_MAY_NOTRETURN (block)
+	      && vn_reference_may_trap (ref))
+	    to_remove = i;
 	}
       else if (expr->kind == NARY)
 	{