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nv50,nvc0: handle SQRT lowering inside the driver

Browse source 
First off, st/mesa lowers DSQRT incorrectly (it uses CMP to attempt to
find out whether the input is less than 0). Secondly the current
approach (x * rsq(x)) behaves poorly for x = inf - a NaN is produced
instead of inf.

Instead we switch to the less accurate rcp(rsq(x)) method - this behaves
nicely for all valid inputs. We still don't do this for DSQRT since the
RSQ/RCP ops are *really* inaccurate, and don't even have Newton-Raphson
steps right now. Eventually we should have a separate library function
for DSQRT that does it more precisely (and perhaps move this lowering to
the post-opt phase).

This fixes a number of dEQP precision tests that were expecting better
behavior for infinite inputs.

Signed-off-by: Ilia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Tested-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
This commit is contained in:
Ilia Mirkin 2016-03-12 21:26:21 -05:00
parent b3e7fb5234
commit c1e4a6bfbf
6 changed files with 27 additions and 23 deletions
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6
src/gallium/drivers/nouveau/codegen/nv50_ir_build_util.cpp
View file

@ -585,6 +585,7 @@ BuildUtil::split64BitOpPostRA(Function *fn, Instruction *i,
return NULL;
srcNr = 2;
break;
case OP_SELP: srcNr = 3; break;
default:
// TODO when needed
return NULL;
@ -601,7 +602,10 @@ BuildUtil::split64BitOpPostRA(Function *fn, Instruction *i,
for (int s = 0; s < srcNr; ++s) {
if (lo->getSrc(s)->reg.size < 8) {
hi->setSrc(s, zero);
if (s == 2)
hi->setSrc(s, lo->getSrc(s));
else
hi->setSrc(s, zero);
} else {
if (lo->getSrc(s)->refCount() > 1)
lo->setSrc(s, cloneShallow(fn, lo->getSrc(s)));

2
src/gallium/drivers/nouveau/codegen/nv50_ir_from_tgsi.cpp
View file

@ -616,6 +616,7 @@ static nv50_ir::operation translateOpcode(uint opcode)
NV50_IR_OPCODE_CASE(RCP, RCP);
NV50_IR_OPCODE_CASE(RSQ, RSQ);
NV50_IR_OPCODE_CASE(SQRT, SQRT);
NV50_IR_OPCODE_CASE(MUL, MUL);
NV50_IR_OPCODE_CASE(ADD, ADD);
@ -2689,6 +2690,7 @@ Converter::handleInstruction(const struct tgsi_full_instruction *insn)
case TGSI_OPCODE_FLR:
case TGSI_OPCODE_TRUNC:
case TGSI_OPCODE_RCP:
case TGSI_OPCODE_SQRT:
case TGSI_OPCODE_IABS:
case TGSI_OPCODE_INEG:
case TGSI_OPCODE_NOT:

7
src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nv50.cpp
View file

@ -1203,10 +1203,9 @@ NV50LoweringPreSSA::handleDIV(Instruction *i)
bool
NV50LoweringPreSSA::handleSQRT(Instruction *i)
{
Instruction *rsq = bld.mkOp1(OP_RSQ, TYPE_F32,
bld.getSSA(), i->getSrc(0));
i->op = OP_MUL;
i->setSrc(1, rsq->getDef(0));
bld.setPosition(i, true);
i->op = OP_RSQ;
bld.mkOp1(OP_RCP, i->dType, i->getDef(0), i->getDef(0));
return true;
}

31
src/gallium/drivers/nouveau/codegen/nv50_ir_lowering_nvc0.cpp
View file

@ -1778,22 +1778,21 @@ NVC0LoweringPass::handleMOD(Instruction *i)
bool
NVC0LoweringPass::handleSQRT(Instruction *i)
{
Value *pred = bld.getSSA(1, FILE_PREDICATE);
Value *zero = bld.getSSA();
Instruction *rsq;
bld.mkOp1(OP_MOV, TYPE_U32, zero, bld.mkImm(0));
if (i->dType == TYPE_F64)
zero = bld.mkOp2v(OP_MERGE, TYPE_U64, bld.getSSA(8), zero, zero);
bld.mkCmp(OP_SET, CC_LE, i->dType, pred, i->dType, i->getSrc(0), zero);
bld.mkOp1(OP_MOV, i->dType, i->getDef(0), zero)->setPredicate(CC_P, pred);
rsq = bld.mkOp1(OP_RSQ, i->dType,
bld.getSSA(typeSizeof(i->dType)), i->getSrc(0));
rsq->setPredicate(CC_NOT_P, pred);
i->op = OP_MUL;
i->setSrc(1, rsq->getDef(0));
i->setPredicate(CC_NOT_P, pred);
if (i->dType == TYPE_F64) {
Value *pred = bld.getSSA(1, FILE_PREDICATE);
Value *zero = bld.loadImm(NULL, 0.0d);
Value *dst = bld.getSSA(8);
bld.mkOp1(OP_RSQ, i->dType, dst, i->getSrc(0));
bld.mkCmp(OP_SET, CC_LE, i->dType, pred, i->dType, i->getSrc(0), zero);
bld.mkOp3(OP_SELP, TYPE_U64, dst, zero, dst, pred);
i->op = OP_MUL;
i->setSrc(1, dst);
// TODO: Handle this properly with a library function
} else {
bld.setPosition(i, true);
i->op = OP_RSQ;
bld.mkOp1(OP_RCP, i->dType, i->getDef(0), i->getDef(0));
}
return true;
}

2
src/gallium/drivers/nouveau/nv50/nv50_screen.c
View file

@ -305,7 +305,7 @@ nv50_screen_get_shader_param(struct pipe_screen *pscreen, unsigned shader,
case PIPE_SHADER_CAP_TGSI_CONT_SUPPORTED:
return 1;
case PIPE_SHADER_CAP_TGSI_SQRT_SUPPORTED:
return 0;
return 1;
case PIPE_SHADER_CAP_SUBROUTINES:
return 0; /* please inline, or provide function declarations */
case PIPE_SHADER_CAP_INTEGERS:

2
src/gallium/drivers/nouveau/nvc0/nvc0_screen.c
View file

@ -328,7 +328,7 @@ nvc0_screen_get_shader_param(struct pipe_screen *pscreen, unsigned shader,
case PIPE_SHADER_CAP_TGSI_CONT_SUPPORTED:
return 1;
case PIPE_SHADER_CAP_TGSI_SQRT_SUPPORTED:
return 0;
return 1;
case PIPE_SHADER_CAP_SUBROUTINES:
return 1;
case PIPE_SHADER_CAP_INTEGERS: