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gallium/tgsi: Treat UCMP sources as floats to match the GLSL-to-TGSI pass expectations. 

Currently the GLSL-to-TGSI translation pass assumes it can use
floating point source modifiers on the UCMP instruction.  See the bug
report linked below for an example where an unrelated change in the
GLSL built-in lowering code for atan2 (e9ffd12827)
caused the generation of floating-point ir_unop_neg instructions
followed by ir_triop_csel, which is translated into UCMP with a negate
modifier on back-ends with native integer support.

Allowing floating-point source modifiers on an integer instruction
seems like rather dubious design for a transport IR, since the same
semantics could be represented as a sequence of MOV+UCMP instructions
instead, but supposedly this matches the expectations of TGSI
back-ends other than tgsi_exec, and the expectations of the DX10 API.
I take no responsibility for future headaches caused by this
inconsistency.

Fixes a regression of piglit glsl-fs-tan-1 on softpipe introduced by
the above-mentioned glsl front-end commit.  Even though the commit
that triggered the regression doesn't seem to have made it to any
stable branches yet, this might be worth back-porting since I don't
see any reason why the bug couldn't have been reproduced before that
point.

Suggested-by: Roland Scheidegger <sroland@vmware.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=99817
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
This commit is contained in:
Francisco Jerez 2017-03-13 17:31:39 -07:00
parent eb5a61f77a
commit e6469ec43b
2 changed files with 46 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
src/gallium/auxiliary/tgsi/tgsi_exec.c
View File

@ -3358,6 +3358,46 @@ exec_up2h(struct tgsi_exec_machine *mach,
}
}
static void
micro_ucmp(union tgsi_exec_channel *dst,
const union tgsi_exec_channel *src0,
const union tgsi_exec_channel *src1,
const union tgsi_exec_channel *src2)
{
dst->f[0] = src0->u[0] ? src1->f[0] : src2->f[0];
dst->f[1] = src0->u[1] ? src1->f[1] : src2->f[1];
dst->f[2] = src0->u[2] ? src1->f[2] : src2->f[2];
dst->f[3] = src0->u[3] ? src1->f[3] : src2->f[3];
}
static void
exec_ucmp(struct tgsi_exec_machine *mach,
const struct tgsi_full_instruction *inst)
{
unsigned int chan;
struct tgsi_exec_vector dst;
for (chan = 0; chan < TGSI_NUM_CHANNELS; chan++) {
if (inst->Dst[0].Register.WriteMask & (1 << chan)) {
union tgsi_exec_channel src[3];
fetch_source(mach, &src[0], &inst->Src[0], chan,
TGSI_EXEC_DATA_UINT);
fetch_source(mach, &src[1], &inst->Src[1], chan,
TGSI_EXEC_DATA_FLOAT);
fetch_source(mach, &src[2], &inst->Src[2], chan,
TGSI_EXEC_DATA_FLOAT);
micro_ucmp(&dst.xyzw[chan], &src[0], &src[1], &src[2]);
}
}
for (chan = 0; chan < TGSI_NUM_CHANNELS; chan++) {
if (inst->Dst[0].Register.WriteMask & (1 << chan)) {
store_dest(mach, &dst.xyzw[chan], &inst->Dst[0], inst, chan,
TGSI_EXEC_DATA_FLOAT);
}
}
}
static void
exec_scs(struct tgsi_exec_machine *mach,
const struct tgsi_full_instruction *inst)
@ -4997,18 +5037,6 @@ micro_uarl(union tgsi_exec_channel *dst,
dst->i[3] = src->u[3];
}
static void
micro_ucmp(union tgsi_exec_channel *dst,
const union tgsi_exec_channel *src0,
const union tgsi_exec_channel *src1,
const union tgsi_exec_channel *src2)
{
dst->u[0] = src0->u[0] ? src1->u[0] : src2->u[0];
dst->u[1] = src0->u[1] ? src1->u[1] : src2->u[1];
dst->u[2] = src0->u[2] ? src1->u[2] : src2->u[2];
dst->u[3] = src0->u[3] ? src1->u[3] : src2->u[3];
}
/**
* Signed bitfield extract (i.e. sign-extend the extracted bits)
*/
@ -5911,7 +5939,7 @@ exec_instruction(
break;
case TGSI_OPCODE_UCMP:
exec_vector_trinary(mach, inst, micro_ucmp, TGSI_EXEC_DATA_UINT, TGSI_EXEC_DATA_UINT);
exec_ucmp(mach, inst);
break;
case TGSI_OPCODE_IABS:

8
src/gallium/docs/source/tgsi.rst
View File

@ -28,9 +28,11 @@ Modifiers
TGSI supports modifiers on inputs (as well as saturate modifier on instructions).
For inputs which have a floating point type, both absolute value and negation
modifiers are supported (with absolute value being applied first).
TGSI_OPCODE_MOV is considered to have float input type for applying modifiers.
For inputs which have a floating point type, both absolute value and
negation modifiers are supported (with absolute value being applied
first). The only source of TGSI_OPCODE_MOV and the second and third
sources of TGSI_OPCODE_UCMP are considered to have float type for
applying modifiers.
For inputs which have signed or unsigned type only the negate modifier is
supported.