[PATCH][AArch64] Increase static buffer size in aarch64_rewrite_selected_cpu

[Kyrill Tkachov]

Hi all,

When trying to compile a testcase with -mcpu=cortex-a57+crypto+nocrc I got the 
weird assembler error:
Assembler messages:
Error: missing architectural extension
Error: unrecognized option -mcpu=cortex-a57+crypto+no

The problem is the aarch64_rewrite_selected_cpu that is used to rewrite -mcpu 
for big.LITTLE options
has a limit of 20 characters in what it handles, which we can exhaust quickly 
if we specify
architectural extensions in a fine-grained manner.

This patch increases that character limit to 128 and adds an assert to confirm 
that no bad things
happen.


It also fixes another problem: If we pass a big.LITTLE combination with feature 
modifiers like:
-mcpu=cortex-a57.cortex-a53+nosimd

the code will truncate everything after '.', thus destroying the extensions 
that we want to pass.
The patch adds code to stitch the extensions back on after the LITTLE cpu is 
removed.

Tested aarch64-none-elf and made sure the given mcpu option works fine with the 
assembler.

Ok for trunk?

Thanks,
Kyrill

2015-04-20  Kyrylo Tkachov  <kyrylo.tkac...@arm.com>

    * common/config/aarch64/aarch64-common.c (AARCH64_CPU_NAME_LENGTH):
    Increase to 128.
    (aarch64_rewrite_selected_cpu): Do not chop off extensions starting
    at '.'.  Assert that there's enough space for everything.

commit 9623c859d5f4d0da1a364184bf0ce0dbbc7907b4
Author: Kyrylo Tkachov <kyrylo.tkac...@arm.com>
Date:   Thu Feb 19 17:05:48 2015 +0000

    [AArch64] Increase static buffer size in aarch64_rewrite_selected_cpu

diff --git a/gcc/common/config/aarch64/aarch64-common.c b/gcc/common/config/aarch64/aarch64-common.c
index 308f19c..b3fd9dc 100644
--- a/gcc/common/config/aarch64/aarch64-common.c
+++ b/gcc/common/config/aarch64/aarch64-common.c
@@ -27,6 +27,7 @@
 #include "common/common-target-def.h"
 #include "opts.h"
 #include "flags.h"
+#include "errors.h"
 
 #ifdef  TARGET_BIG_ENDIAN_DEFAULT
 #undef  TARGET_DEFAULT_TARGET_FLAGS
@@ -89,23 +90,34 @@ aarch64_handle_option (struct gcc_options *opts,
 
 struct gcc_targetm_common targetm_common = TARGETM_COMMON_INITIALIZER;
 
-#define AARCH64_CPU_NAME_LENGTH 20
+#define AARCH64_CPU_NAME_LENGTH 128
 
-/* Truncate NAME at the first '.' character seen, or return
-   NAME unmodified.  */
+/* Truncate NAME at the first '.' character seen up to the first '+'
+   or return NAME unmodified.  */
 
 const char *
 aarch64_rewrite_selected_cpu (const char *name)
 {
   static char output_buf[AARCH64_CPU_NAME_LENGTH + 1] = {0};
-  char *arg_pos;
+  const char *bL_sep;
+  const char *feats;
+  size_t pref_size;
+  size_t feat_size;
 
-  strncpy (output_buf, name, AARCH64_CPU_NAME_LENGTH);
-  arg_pos = strchr (output_buf, '.');
+  bL_sep = strchr (name, '.');
+  if (!bL_sep)
+    return name;
 
-  /* If we found a '.' truncate the entry at that point.  */
-  if (arg_pos)
-    *arg_pos = '\0';
+  feats = strchr (name, '+');
+  feat_size = feats ? strnlen (feats, AARCH64_CPU_NAME_LENGTH) : 0;
+  pref_size = bL_sep - name;
+
+  if ((feat_size + pref_size) > AARCH64_CPU_NAME_LENGTH)
+    internal_error ("-mcpu string too large");
+
+  strncpy (output_buf, name, pref_size);
+  if (feats)
+    strncpy (output_buf + pref_size, feats, feat_size);
 
   return output_buf;
 }