ld: Set non_ir_ref_regular on source for assignment

We need to set non_ir_ref_regular on the source for assignment to get
the correct LTO resolution:

190 a27be7f4ad90c5ce PREVAILING_DEF real_g

instead of

190 30c3b2d8f967f5ea PREVAILING_DEF_IRONLY real_g

	PR ld/26163
	* ldexp.c (exp_fold_tree_1): Set non_ir_ref_regular on the source
	for assignment.
	* testsuite/ld-plugin/lto.exp: Run ld/26163 test.
	* testsuite/ld-plugin/pr26163a.c: New file.
	* testsuite/ld-plugin/pr26163b.c: Likewise.

ld/ChangeLog

@@ -1,3 +1,12 @@
+2020-06-24  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/26163
+	* ldexp.c (exp_fold_tree_1): Set non_ir_ref_regular on the source
+	for assignment.
+	* testsuite/ld-plugin/lto.exp: Run ld/26163 test.
+	* testsuite/ld-plugin/pr26163a.c: New file.
+	* testsuite/ld-plugin/pr26163b.c: Likewise.
+
 2020-06-24  Alan Modra  <amodra@gmail.com>
 
 	* lexsup.c (elf_shlib_list_options): Properly format help message.

ld/ldexp.c

@@ -1217,15 +1217,19 @@ exp_fold_tree_1 (etree_type *tree)
 			bfd_link_hide_symbol (link_info.output_bfd,
 					      &link_info, h);
 
-		      /* Copy the symbol type if this is an expression only
+		      /* Copy the symbol type and set non_ir_ref_regular
+			 on the source if this is an expression only
 			 referencing a single symbol.  (If the expression
 			 contains ternary conditions, ignoring symbols on
 			 false branches.)  */
 		      if (expld.assign_src != NULL
 			  && (expld.assign_src
 			      != (struct bfd_link_hash_entry *) -1))
-			bfd_copy_link_hash_symbol_type (link_info.output_bfd,
-							h, expld.assign_src);
+			{
+			  bfd_copy_link_hash_symbol_type (link_info.output_bfd,
+							  h, expld.assign_src);
+			  expld.assign_src->non_ir_ref_regular = TRUE;
+			}
 		    }
 		}
 	    }

ld/testsuite/ld-plugin/lto.exp

@@ -207,6 +207,9 @@ set lto_link_tests [list \
   [list "Build pr24406-2b.o" \
    "" "-O2 -fno-lto" \
    {pr24406-2b.c}] \
+  [list "Build pr26163a.o" \
+   "" "-O2 -fno-lto" \
+   {pr26163a.c}] \
 ]
 
 if { [at_least_gcc_version 10 0] } {
@@ -502,6 +505,11 @@ set lto_run_tests [list \
    {pr24406-2a.c} "pr24406-2" "pass.out" \
    "-flto -O2" "c" "" \
    "tmpdir/pr24406-2b.o -Wl,--wrap=cook"] \
+  [list "Run pr26163" \
+   "-O2 -flto" "" \
+   {pr26163b.c} "pr24406-2" "pass.out" \
+   "-flto -O2" "c" "" \
+   "tmpdir/pr26163a.o -Wl,--defsym,g=real_g"] \
 ]
 
 if { [at_least_gcc_version 4 7] } {

ld/testsuite/ld-plugin/pr26163a.c

@@ -0,0 +1,9 @@
+extern int counter;
+
+extern void g(void);
+
+void f(void)
+{
+  g();
+  counter++;
+}

ld/testsuite/ld-plugin/pr26163b.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+
+int counter;
+extern void f(void);
+
+void
+real_g(void)
+{
+  counter++;
+}
+
+int main()
+{
+  real_g();
+  f();
+  if (counter == 3)
+    printf ("PASS\n");
+  return 0;
+}