The following patch solves
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85030
The patch was successfully bootstrapped on x86 and x86-64 and tested
on x86-64.
Committed as rev. 258820.
Index: ChangeLog
===================================================================
--- ChangeLog (revision 258819)
+++ ChangeLog (working copy)
@@ -1,3 +1,9 @@
+2018-03-23 Vladimir Makarov <vmaka...@redhat.com>
+
+ PR inline-asm/85030
+ * lra-constraints.c (process_alt_operands): Don't match BLKmode
+ and non BLKmode operands.
+
2018-03-23 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
PR target/85026
Index: testsuite/ChangeLog
===================================================================
--- testsuite/ChangeLog (revision 258819)
+++ testsuite/ChangeLog (working copy)
@@ -1,3 +1,8 @@
+2018-03-23 Vladimir Makarov <vmaka...@redhat.com>
+
+ PR inline-asm/85030
+ * testsuite/gcc.target/i386/pr85030.c: New.
+
2018-03-23 Kyrylo Tkachov <kyrylo.tkac...@arm.com>
PR target/85026
Index: lra-constraints.c
===================================================================
--- lra-constraints.c (revision 258691)
+++ lra-constraints.c (working copy)
@@ -2118,6 +2118,14 @@ process_alt_operands (int only_alternati
GET_MODE_SIZE (biggest_mode[nop])))
break;
+ /* Don't match wrong asm insn operands for proper
+ diagnostic later. */
+ if (INSN_CODE (curr_insn) < 0
+ && (curr_operand_mode[m] == BLKmode
+ || curr_operand_mode[nop] == BLKmode)
+ && curr_operand_mode[m] != curr_operand_mode[nop])
+ break;
+
this_alternative_matches = m;
m_hregno = get_hard_regno (*curr_id->operand_loc[m], false);
/* We are supposed to match a previous operand.
Index: testsuite/gcc.target/i386/pr85030.c
===================================================================
--- testsuite/gcc.target/i386/pr85030.c (nonexistent)
+++ testsuite/gcc.target/i386/pr85030.c (working copy)
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O1" } */
+struct S { int c, *b, *e; };
+
+void
+foo ()
+{
+ struct S a;
+ asm volatile ("" : "=rm" (a) : "0" (1)); /* { dg-error "inconsistent operand constraints in an 'asm'" } */
+}
