[PATCH v2] x86: actually implement .noopt

[Jan Beulich <jbeulich@suse.com>]

For quite some time we've had support for -O command line options. With
that ignoring at least .noopt isn't really a good idea.

Re-purpose the optimize-3 test for testing this directive's effect as
well.

As to the doc addition - this uses the same text as is there for the
{nooptimize} pseudo-prefix, despite me not being convinced of the "size"
part being fully accurate there (and hence also here).
---
I haven't been able to find any applicable documentation for other
(perhaps legacy) assemblers' support of .noopt (and .optim). An option
to also handle .optim would be to
- restore previously saved settings (if optimization was enabled on the
  command line),
- enable a pre-determined level of optimization if optimization was not
  enabled on the command line.
Thoughts?
---
v2: Deal with possible arguments.

--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -139,6 +139,7 @@ arch_entry;
 
 static void update_code_flag (int, int);
 static void s_insn (int);
+static void s_noopt (int);
 static void set_code_flag (int);
 static void set_16bit_gcc_code_flag (int);
 static void set_intel_syntax (int);
@@ -1231,7 +1232,7 @@ const pseudo_typeS md_pseudo_table[] =
   {"value", cons, 2},
   {"slong", signed_cons, 4},
   {"insn", s_insn, 0},
-  {"noopt", s_ignore, 0},
+  {"noopt", s_noopt, 0},
   {"optim", s_ignore, 0},
   {"code16gcc", set_16bit_gcc_code_flag, CODE_16BIT},
   {"code16", set_code_flag, CODE_16BIT},
@@ -4992,6 +4993,18 @@ optimize_encoding (void)
     }
 }
 
+static void
+s_noopt (int dummy ATTRIBUTE_UNUSED)
+{
+  if (!is_it_end_of_statement ())
+    as_warn (_("`.noopt' arguments ignored"));
+
+  optimize = 0;
+  optimize_for_space = 0;
+
+  ignore_rest_of_line ();
+}
+
 /* Return non-zero for load instruction.  */
 
 static int
--- a/gas/doc/c-i386.texi
+++ b/gas/doc/c-i386.texi
@@ -763,6 +763,10 @@ be suffixed by @code{@{:d@var{n}@}} to s
 This can be combined with an embedded broadcast specifier:
 @samp{8(%eax)@{1to8:d8@}}.
 
+@cindex @code{noopt} directive
+@item .noopt
+Disable instruction size optimization.
+
 @c FIXME: Document other x86 specific directives ?  Eg: .code16gcc,
 
 @end table
--- a/gas/testsuite/gas/i386/i386.exp
+++ b/gas/testsuite/gas/i386/i386.exp
@@ -614,6 +614,7 @@ if [gas_32_check] then {
     run_list_test "optimize-6a" "-I${srcdir}/$subdir -march=+noavx -al"
     run_dump_test "optimize-6b"
     run_list_test "optimize-7" "-I${srcdir}/$subdir -march=+noavx2 -al"
+    run_dump_test "noopt"
     run_dump_test "lea-optimize"
     run_dump_test "lea16-optimize"
     run_dump_test "lea16-optimize2"
--- /dev/null
+++ b/gas/testsuite/gas/i386/noopt.d
@@ -0,0 +1,4 @@
+#as: -Os -I${srcdir}/$subdir
+#objdump: -drw
+#name: .noopt directive
+#dump: optimize-3.d
--- /dev/null
+++ b/gas/testsuite/gas/i386/noopt.s
@@ -0,0 +1,2 @@
+	.noopt
+	.include "optimize-3.s"
--- a/gas/testsuite/gas/i386/optimize-3.d
+++ b/gas/testsuite/gas/i386/optimize-3.d
@@ -1,4 +1,4 @@
-#as: -Os
+#as: -Os --defsym USE_PREFIX=1
 #objdump: -drw
 #name: optimized encoding 3 with -Os
 
--- a/gas/testsuite/gas/i386/optimize-3.s
+++ b/gas/testsuite/gas/i386/optimize-3.s
@@ -1,24 +1,32 @@
 # Check instructions with optimized encoding
 
+	.macro noopt insn:vararg
+	.ifdef USE_PREFIX
+	{nooptimize} \insn
+	.else
+	\insn
+	.endif
+	.endm
+
 	.text
 _start:
-	{nooptimize} testl $0x7f, %eax
+	noopt testl $0x7f, %eax
 
-	{nooptimize} lock xchg	%ecx, (%edx)
-	{nooptimize} lock xchg	(%ecx), %edx
+	noopt lock xchg	%ecx, (%edx)
+	noopt lock xchg	(%ecx), %edx
 
-	{nooptimize} vmovdqa32	%ymm1, %ymm2
-	{nooptimize} vmovdqa64	%ymm1, %ymm2
-	{nooptimize} vmovdqu8	%xmm1, %xmm2
-	{nooptimize} vmovdqu16	%xmm1, %xmm2
-	{nooptimize} vmovdqu32	%xmm1, %xmm2
-	{nooptimize} vmovdqu64	%xmm1, %xmm2
+	noopt vmovdqa32	%ymm1, %ymm2
+	noopt vmovdqa64	%ymm1, %ymm2
+	noopt vmovdqu8	%xmm1, %xmm2
+	noopt vmovdqu16	%xmm1, %xmm2
+	noopt vmovdqu32	%xmm1, %xmm2
+	noopt vmovdqu64	%xmm1, %xmm2
 
-	{nooptimize} vpandd	%xmm2, %xmm3, %xmm4
-	{nooptimize} vpandq	%ymm2, %ymm3, %ymm4
-	{nooptimize} vpandnd	%ymm2, %ymm3, %ymm4
-	{nooptimize} vpandnq	%xmm2, %xmm3, %xmm4
-	{nooptimize} vpord	%xmm2, %xmm3, %xmm4
-	{nooptimize} vporq	%ymm2, %ymm3, %ymm4
-	{nooptimize} vpxord	%ymm2, %ymm3, %ymm4
-	{nooptimize} vpxorq	%xmm2, %xmm3, %xmm4
+	noopt vpandd	%xmm2, %xmm3, %xmm4
+	noopt vpandq	%ymm2, %ymm3, %ymm4
+	noopt vpandnd	%ymm2, %ymm3, %ymm4
+	noopt vpandnq	%xmm2, %xmm3, %xmm4
+	noopt vpord	%xmm2, %xmm3, %xmm4
+	noopt vporq	%ymm2, %ymm3, %ymm4
+	noopt vpxord	%ymm2, %ymm3, %ymm4
+	noopt vpxorq	%xmm2, %xmm3, %xmm4