Nouveau - May 2014 - [Bug 79462] New: [NVC0/Codegen] Shader compilation falis in spill logic

https://bugs.freedesktop.org/show_bug.cgi?id=79462

          Priority: medium
            Bug ID: 79462
          Assignee: nouveau at lists.freedesktop.org
           Summary: [NVC0/Codegen] Shader compilation falis in spill logic
          Severity: normal
    Classification: Unclassified
                OS: All
          Reporter: imirkin at alum.mit.edu
          Hardware: Other
            Status: NEW
           Version: unspecified
         Component: Drivers/DRI/nouveau
           Product: Mesa

Created attachment 100179
  --> https://bugs.freedesktop.org/attachment.cgi?id=100179&action=edit
failing tgsi shader

The attached shader fails in the RA step, when inserting spill code:

nv50_ir::SpillCodeInserter::run (this=0x7ffffffec0c0, lst=std::list)
    at codegen/nv50_ir_ra.cpp:1561
1561             while (!dval->uses.empty()) {

Easily reproduced with nouveau_compiler -a c0. Apparently this shader is
generated as part of the d3d9 st, with skyrimlauncher, when it's trying to
detect the graphics card.

dval is null, which means that something out there isn't an lvalue. Or, in
this
case, apparently a null value??

(gdb) p *defi
$4 = {_vptr.Instruction = 0x86e570, next = 0x0, prev = 0x0, id = -1, serial 27,
op = nv50_ir::OP_SPLIT,
  dType = nv50_ir::TYPE_B128, sType = nv50_ir::TYPE_B128, cc = nv50_ir::CC_TR,
rnd = nv50_ir::ROUND_N, 
  cache = nv50_ir::CACHE_CA, subOp = 0, encSize = 0, saturate = 0, join = 0,
fixed = 0, terminator = 0, 
  ftz = 0, dnz = 0, ipa = 0, lanes = 15, perPatch = 0, exit = 0, mask = 0,
postFactor = 0 '\000', 
  predSrc = -1 '\377', flagsDef = -1 '\377', flagsSrc = -1
'\377', sched = 0,
bb = 0x0, 
  defs = std::deque with 4 elements = {{value = 0x0, origin = 0x0, insn 0x200},
{value = 0x85ce30,
      origin = 0x7ffff71a0698 <main_arena+88>, insn = 0x9e5e40}, {value =
0x0,
origin = 0x0, 
      insn = 0x9e5e40}, {value = 0x0, origin = 0x0, insn = 0x9e5e40}}, 
  srcs = std::deque with 1 elements = {{mod = {bits = 0 '\000'},
indirect "\377\377",
      swizzle = 0 '\000', usedAsPtr = false, value = 0x0, insn =
0x200}}}

Note that the second def isn't null but the others are? Perhaps this happens
as
part of dead code elimination? Need to investigate more.

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https://bugs.freedesktop.org/show_bug.cgi?id=79462

--- Comment #1 from Ilia Mirkin <imirkin at alum.mit.edu> ---
The below patch helps avoid the crash, but it still still generate incorrect
code. I think there are a few issues here, and I'll have to think a little
harder about how to properly resolve them.


diff --git a/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
b/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
index 5ab6570..89c83cb 100644
--- a/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
+++ b/src/gallium/drivers/nouveau/codegen/nv50_ir_ra.cpp
@@ -1576,7 +1576,8 @@ SpillCodeInserter::run(const
std::list<ValuePair>& lst)

          assert(defi);
          if (defi->isPseudo()) {
-            d = lval->defs.erase(d);
+            while (d != lval->defs.end() && (*d)->getInsn() ==
defi)
+               d = lval->defs.erase(d);
             --d;
             if (slot->reg.file == FILE_MEMORY_LOCAL)
                delete_Instruction(func->getProgram(), defi);

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--- Comment #2 from Ilia Mirkin <imirkin at alum.mit.edu> ---
I've spent a bunch of time looking at this issue.

So *one* of the problems is that we delete the instruction too early. But I
think there's more going on. Still debugging. The issue happens if we want
to
spill a value that is split.

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--- Comment #3 from Ilia Mirkin <imirkin at alum.mit.edu> ---
http://patchwork.freedesktop.org/patch/34098/

Please see if this helps.

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Ilia Mirkin <imirkin at alum.mit.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Ilia Mirkin <imirkin at alum.mit.edu> ---
I've pushed out the fix, makes at least the attached shader compile. It also
fixed UE4 demos which appear to render fine. Should get backported to 10.3 and
probably 10.2 as well.

commit 0147c10c5f00b43696ba660aab604d674a75e83c
Author: Ilia Mirkin <imirkin at alum.mit.edu>
Date:   Wed Sep 24 21:45:07 2014 -0400

    nv50/ir: avoid deleting pseudo instructions too early

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