Commit Graph

15 Commits

Author SHA1 Message Date
Richard Sandiford f722a8e30e [SystemZ] Improve handling of SETCC
We previously used the default expansion to SELECT_CC, which in turn would
expand to "LHI; BRC; LHI".  In most cases it's better to use an IPM-based
sequence instead.

llvm-svn: 192784
2013-10-16 11:10:55 +00:00
Richard Sandiford 4943bc393a [SystemZ] Use XC for a memset of 0
llvm-svn: 190130
2013-09-06 10:25:07 +00:00
Richard Sandiford be133a8757 [SystemZ] Extend memcmp support to all constant lengths
This uses the infrastructure added for memcpy and memmove in r189331.

llvm-svn: 189458
2013-08-28 09:01:51 +00:00
Richard Sandiford 5e318f0bfe [SystemZ] Extend memcpy and memset support to all constant lengths
Lengths up to a certain threshold (currently 6 * 256) use a series of MVCs.
Lengths above that threshold use a loop to handle X*256 bytes followed
by a single MVC to handle the excess (if any).  This loop will also be
needed in future when support for variable lengths is added.

Because the same tablegen classes are used to define MVC and CLC,
the patch also has the side-effect of defining a pseudo loop instruction
for CLC.  That instruction isn't used yet (and wouldn't be handled correctly
if it were).  I'm planning to use it soon though.

llvm-svn: 189331
2013-08-27 09:54:29 +00:00
Richard Sandiford 6f6d55161b [SystemZ] Use SRST to optimize memchr
SystemZTargetLowering::emitStringWrapper() previously loaded the character
into R0 before the loop and made R0 live on entry.  I'd forgotten that
allocatable registers weren't allowed to be live across blocks at this stage,
and it confused LiveVariables enough to cause a miscompilation of f3 in
memchr-02.ll.

This patch instead loads R0 in the loop and leaves LICM to hoist it
after RA.  This is actually what I'd tried originally, but I went for
the manual optimisation after noticing that R0 often wasn't being hoisted.
This bug forced me to go back and look at why, now fixed as r188774.

We should also try to optimize null checks so that they test the CC result
of the SRST directly.  The select between null and the SRST GPR result could
then usually be deleted as dead.

llvm-svn: 188779
2013-08-20 09:38:48 +00:00
Richard Sandiford 0dec06a28c [SystemZ] Use SRST to implement strlen and strnlen
It would also make sense to use it for memchr; I'm working on that now.

llvm-svn: 188547
2013-08-16 11:41:43 +00:00
Richard Sandiford bb83a50f57 [SystemZ] Use MVST to implement strcpy and stpcpy
llvm-svn: 188546
2013-08-16 11:29:37 +00:00
Richard Sandiford ca23271010 [SystemZ] Use CLST to implement strcmp
llvm-svn: 188544
2013-08-16 11:21:54 +00:00
Richard Sandiford a59012577c [SystemZ] Fix sign of integer memcmp result
r188163 used CLC to implement memcmp.  Code that compares the result
directly against zero can test the CC value produced by CLC, but code
that needs an integer result must use IPM.  The sequence I'd used was:

   ipm <reg>
   sll <reg>, 2
   sra <reg>, 30

but I'd forgotten that this inverts the order, so that CC==1 ("less")
becomes an integer greater than zero, and CC==2 ("greater") becomes
an integer less than zero.  This sequence should only be used if the
CLC arguments are reversed to compensate.  The problem then is that
the branch condition must also be reversed when testing the CLC
result directly.

Rather than do that, I went for a different sequence that works with
the natural CLC order:

   ipm <reg>
   srl <reg>, 28
   rll <reg>, <reg>, 31

One advantage of this is that it doesn't clobber CC.  A disadvantage
is that any sign extension to 64 bits must be done separately,
rather than being folded into the shifts.

llvm-svn: 188538
2013-08-16 10:22:54 +00:00
Richard Sandiford 564681c88d [SystemZ] Use CLC and IPM to implement memcmp
For now this is restricted to fixed-length comparisons with a length
in the range [1, 256], as for memcpy() and MVC.

llvm-svn: 188163
2013-08-12 10:28:10 +00:00
Richard Sandiford 47660c148c [SystemZ] Use "STC;MVC" for memset
Use "STC;MVC" for memsets that are too big for two STCs or MV...Is yet
small enough for a single MVC.  As with memcpy, I'm leaving longer cases
till later.

The number of tests might seem excessive, but f33 & f34 from memset-04.ll
failed the first cut because I'd not added the "?:" on the calculation
of Size1.

llvm-svn: 185918
2013-07-09 09:32:42 +00:00
Richard Sandiford d131ff8cf8 [SystemZ] Use MVC for memcpy
Use MVC for memcpy in cases where a single MVC is enough.  Using MVC is
a win for longer copies too, but I'll leave that for later.

llvm-svn: 185802
2013-07-08 09:35:23 +00:00
Dan Gohman dfc96aea90 Remove the SystemZ backend.
llvm-svn: 142878
2011-10-24 23:48:32 +00:00
Dan Gohman bb919dfb6b Implement a bunch more TargetSelectionDAGInfo infrastructure.
Move EmitTargetCodeForMemcpy, EmitTargetCodeForMemset, and
EmitTargetCodeForMemmove out of TargetLowering and into
SelectionDAGInfo to exercise this.

llvm-svn: 103481
2010-05-11 17:31:57 +00:00
Dan Gohman 9becdddc49 Add skeleton target-specific SelectionDAGInfo files.
llvm-svn: 101564
2010-04-16 23:04:22 +00:00