[AArch64][TLSLE][1/3] Add the option "-mtls-size" for AArch64

[Jiong Wang <jiong dot wang at arm dot com>]

Marcus Shawcroft writes:

> On 21 May 2015 at 17:44, Jiong Wang <jiong.wang@arm.com> wrote:
>>
>> This patch add -mtls-size option for AArch64. This option let user to do
>> finer control on code generation for various TLS model on AArch64.
>>
>> For example, for TLS LE, user can specify smaller tls-size, for example
>> 4K which is quite usual, to let AArch64 backend generate more efficient
>> instruction sequences.
>>
>> Currently, -mtls-size accept all integer, then will translate it into
>> 12(4K), 24(16M), 32(4G), 48(256TB) based on the value.
>>
>> no functional change.
>>
>> ok for trunk?
>>
>> 2015-05-20  Jiong Wang  <jiong.wang@arm.com>
>>
>> gcc/
>>   * config/aarch64/aarch64.opt (mtls-size): New entry.
>>   * config/aarch64/aarch64.c (initialize_aarch64_tls_size): New function.
>>   * doc/invoke.texi (AArch64 Options): Document -mtls-size.
>
> +mtls-size=
> +Target RejectNegative Joined UInteger Var(aarch64_tls_size) Init(24)
> +Specifies size of the TLS data area, default size is 16M. Accept any
> integer, but the value
> +will be transformed into 12(4K), 24(16M), 32(4G), 48(256TB)
> +
>
> Can we follow the mechanism used by rs6000 and limit the accepted
> values here using an Enum to just the valid values: 12, 24, 32, 48?

Done.

>
> +@item -mtls-size=@var{size}
> +@opindex mtls-size
> +Specify the size of TLS area. You can specify smaller value to get better code
> +generation for TLS variable access. Currently, we accept any integer, but will
> +turn them into 12(4K), 24(16M), 32(4G), 48(256TB) according to the integer
> +value.
> +
>
> How about:
> "Specify bit size of immediate TLS offsets.  Valid values are 12, 24,
> 32, 48."

Done.

Patch updated, please review, thanks.

2015-08-19  Jiong Wang  <jiong.wang@arm.com>

gcc/
  * config/aarch64/aarch64.opt (mtls-size): New entry.
  * config/aarch64/aarch64.c (initialize_aarch64_tls_size): New function.
  (aarch64_override_options_internal): Call initialize_aarch64_tls_size.
  * doc/invoke.texi (AArch64 Options): Document -mtls-size.

-- 
Regards,
Jiong

From 4a244a1d4b32b1e10e5ba07c0c568f135648912e Mon Sep 17 00:00:00 2001
From: Jiong Wang <jiong.wang@arm.com>
Date: Wed, 19 Aug 2015 14:10:37 +0100
Subject: [PATCH 1/3] 1

---
 gcc/config/aarch64/aarch64.c   | 31 +++++++++++++++++++++++++++++++
 gcc/config/aarch64/aarch64.opt | 19 +++++++++++++++++++
 gcc/doc/invoke.texi            |  5 +++++
 3 files changed, 55 insertions(+)

diff --git a/gcc/config/aarch64/aarch64.c b/gcc/config/aarch64/aarch64.c
index 0f3be3c..f55cc38 100644
--- a/gcc/config/aarch64/aarch64.c
+++ b/gcc/config/aarch64/aarch64.c
@@ -7506,6 +7506,36 @@ aarch64_parse_one_override_token (const char* token,
   return;
 }
 
+/* A checking mechanism for the implementation of the tls size.  */
+
+static void
+initialize_aarch64_tls_size (struct gcc_options *opts)
+{
+  switch (opts->x_aarch64_cmodel_var)
+    {
+    case AARCH64_CMODEL_TINY:
+      /* The maximum TLS size allowed under tiny is 1M.  */
+      if (aarch64_tls_size > 20)
+	aarch64_tls_size = 20;
+      break;
+    case AARCH64_CMODEL_SMALL:
+      /* The maximum TLS size allowed under small is 4G.  */
+      if (aarch64_tls_size > 32)
+	aarch64_tls_size = 32;
+      break;
+    case AARCH64_CMODEL_LARGE:
+      /* The maximum TLS size allowed under large is 16E.
+	 FIXME: 16E should be 64bit, we only support 48bit offset now.  */
+      if (aarch64_tls_size > 48)
+	aarch64_tls_size = 48;
+      break;
+    default:
+      gcc_unreachable ();
+    }
+
+  return;
+}
+
 /* Parse STRING looking for options in the format:
      string	:: option:string
      option	:: name=substring
@@ -7598,6 +7628,7 @@ aarch64_override_options_internal (struct gcc_options *opts)
     }
 
   initialize_aarch64_code_model (opts);
+  initialize_aarch64_tls_size (opts);
 
   aarch64_override_options_after_change_1 (opts);
 }
diff --git a/gcc/config/aarch64/aarch64.opt b/gcc/config/aarch64/aarch64.opt
index 37c2c50..8642bdb 100644
--- a/gcc/config/aarch64/aarch64.opt
+++ b/gcc/config/aarch64/aarch64.opt
@@ -96,6 +96,25 @@ mtls-dialect=
 Target RejectNegative Joined Enum(tls_type) Var(aarch64_tls_dialect) Init(TLS_DESCRIPTORS) Save
 Specify TLS dialect
 
+mtls-size=
+Target RejectNegative Joined Var(aarch64_tls_size) Enum(aarch64_tls_size)
+Specifies bit size of immediate TLS offsets.  Valid values are 12, 24, 32, 48.
+
+Enum
+Name(aarch64_tls_size) Type(int)
+
+EnumValue
+Enum(aarch64_tls_size) String(12) Value(12)
+
+EnumValue
+Enum(aarch64_tls_size) String(24) Value(24)
+
+EnumValue
+Enum(aarch64_tls_size) String(32) Value(32)
+
+EnumValue
+Enum(aarch64_tls_size) String(48) Value(48)
+
 march=
 Target RejectNegative ToLower Joined Var(aarch64_arch_string)
 -march=ARCH	Use features of architecture ARCH
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 27be317..c9f332c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -514,6 +514,7 @@ Objective-C and Objective-C++ Dialects}.
 -mstrict-align @gol
 -momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer @gol
 -mtls-dialect=desc  -mtls-dialect=traditional @gol
+-mtls-size=@var{size} @gol
 -mfix-cortex-a53-835769  -mno-fix-cortex-a53-835769 @gol
 -mfix-cortex-a53-843419  -mno-fix-cortex-a53-843419 @gol
 -march=@var{name}  -mcpu=@var{name}  -mtune=@var{name}}
@@ -12409,6 +12410,10 @@ of TLS variables.  This is the default.
 Use traditional TLS as the thread-local storage mechanism for dynamic accesses
 of TLS variables.
 
+@item -mtls-size=@var{size}
+@opindex mtls-size
+Specify bit size of immediate TLS offsets.  Valid values are 12, 24, 32, 48.
+
 @item -mfix-cortex-a53-835769
 @itemx -mno-fix-cortex-a53-835769
 @opindex mfix-cortex-a53-835769
-- 
1.9.1