[PATCH] Diagnose earlier invalid inline asm constraints (PR inline-asm/84742)

[Jakub Jelinek]

Hi!

We have many loops that use CONSTRAINT_LEN to skip over various constraint
characters, but we assume the constraints have valid length and don't walk
the individual characters to double check this.

If that is not the case, when e.g. 2 character constraint starting letter
is followed by '\0', we'd reject it early (during vregs pass, through
asm_operand_ok).  The PR has different testcase (that fails randomly based
on ASLR), where a 2 character constraint starting letter is followed by ',',
and several spots expect that not to happen (they count number of
alternatives and then for each alternative walk with skipping CONSTRAINT_LEN
characters).

This patch diagnoses this problematic case early as well.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2018-03-08  Jakub Jelinek  <jakub@redhat.com>

	PR inline-asm/84742
	* recog.c (asm_operand_ok): Return 0 if multi-character constraint
	has ',' character inside of it.

	* gcc.target/i386/pr84742-1.c: New test.
	* gcc.target/i386/pr84742-2.c: New test.

--- gcc/recog.c.jj	2018-01-16 09:53:47.000000000 +0100
+++ gcc/recog.c	2018-03-08 14:04:35.889274871 +0100
@@ -1825,7 +1825,7 @@ asm_operand_ok (rtx op, const char *cons
       len = CONSTRAINT_LEN (c, constraint);
       do
 	constraint++;
-      while (--len && *constraint);
+      while (--len && *constraint && *constraint != ',');
       if (len)
 	return 0;
     }
--- gcc/testsuite/gcc.target/i386/pr84742-1.c.jj	2018-03-08 14:11:20.155463943 +0100
+++ gcc/testsuite/gcc.target/i386/pr84742-1.c	2018-03-08 14:12:28.453495882 +0100
@@ -0,0 +1,10 @@
+/* PR inline-asm/84742 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void 
+foo ()
+{
+  char b = 1;
+  asm volatile ("" : "+T,Y" (b));	/* { dg-error "impossible constraint in 'asm'" } */
+}
--- gcc/testsuite/gcc.target/i386/pr84742-2.c.jj	2018-03-08 14:12:37.205499976 +0100
+++ gcc/testsuite/gcc.target/i386/pr84742-2.c	2018-03-08 14:12:52.150506968 +0100
@@ -0,0 +1,10 @@
+/* PR inline-asm/84742 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+void 
+foo ()
+{
+  char b = 1;
+  asm volatile ("" : "+gT,m" (b));	/* { dg-error "impossible constraint in 'asm'" } */
+}

	Jakub