diff mbox

[COMMITTED] tilegx: enable wordsize-64 support for ieee745 dbl-64.

Message ID 201412231905.sBNJ5c3C004622@farm-0002.internal.tilera.com
State Committed
Headers

Commit Message

Chris Metcalf Dec. 23, 2014, 7:04 p.m. UTC 
  I missed this during the initial port.  Some testing shows that
enabling this mode does, unsurprisingly, yield some nice speedups
on the math functions in question.
---
 ChangeLog                   | 4 ++++
 sysdeps/tile/tilegx/Implies | 1 +
 2 files changed, 5 insertions(+)
 create mode 100644 sysdeps/tile/tilegx/Implies

Comments

Joseph Myers Dec. 23, 2014, 8:06 p.m. UTC | #1 
On Tue, 23 Dec 2014, Chris Metcalf wrote:

> I missed this during the initial port.  Some testing shows that
> enabling this mode does, unsurprisingly, yield some nice speedups
> on the math functions in question.

I take it that the ABI on tilegx32 allows the lround alias to llround 
(that is, the upper 32 bits of a return value are unspecified, so that 
when an out-of-range value is passed in the return value always acts 
consistently like some value of type long rather than causing undefined 
behavior in the caller as it would if the ABI requires sign extension or 
zero extension but the result isn't properly extended)?  (That alias 
wouldn't be valid on MIPS n32, as all 32-bit values have to be 
sign-extended in registers - it's architecturally undefined how 32-bit 
instructions behave on 64-bit MIPS when given registers that aren't 
properly sign-extended.)
Chris Metcalf Dec. 23, 2014, 8:47 p.m. UTC | #2 
On 12/23/2014 3:06 PM, Joseph Myers wrote:
> I take it that the ABI on tilegx32 allows the lround alias to llround

No, it doesn't - I missed this possibility.  I assume the best fix is to
provide an lround override in sysdeps/tile/tilegx/tilegx32/s_lround.c
that invokes llround() and then sign-extends the result?

But, why doesn't MIPS itself use this approach?

Thanks for catching this!
Joseph Myers Dec. 23, 2014, 10:31 p.m. UTC | #3 
On Tue, 23 Dec 2014, Chris Metcalf wrote:

> But, why doesn't MIPS itself use this approach?

Use of sysdeps/ieee754/dbl-64/wordsize-64 for MIPS (to the extent 
possible) is on the wiki todo list.
diff mbox

Patch

diff --git a/ChangeLog b/ChangeLog
index 9ed06fd0ff4e..f7bfe913720a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@ 
+2014-12-23  Chris Metcalf  <cmetcalf@ezchip.com>
+
+	* sysdeps/tile/tilegx/Implies: New file.
+
 2014-12-23  Richard Earnshaw  <rearnsha@arm.com>
 
 	* string/stpcpy.c (__stpcpy): Rewrite using strlen and memcpy.
diff --git a/sysdeps/tile/tilegx/Implies b/sysdeps/tile/tilegx/Implies
new file mode 100644
index 000000000000..ade71c1957e8
--- /dev/null
+++ b/sysdeps/tile/tilegx/Implies
@@ -0,0 +1 @@ 
+ieee754/dbl-64/wordsize-64