Re: [Mesa-dev] [PATCH 1/4] r600: use min_dx10/max_dx10 instead of min/max

[Nicolai Hähnle]

On 09.11.2017 18:26, Roland Scheidegger wrote:
Am 09.11.2017 um 18:19 schrieb Jan Vesely:
On Thu, 2017-11-09 at 03:58 +0100, srol...@vmware.com wrote:
From: Roland Scheidegger <srol...@vmware.com>
I believe this is the safe thing to do, especially ever since the driver
actually generates NaNs for muls too.
Albeit since the radeon ISA docs are inaccurate/wrong there, I'm not
entirely sure what the non-dx10 versions do,

non-dx10 version return nan if one of the operands is nan (tested on
Turks).

Yes, I've modified a piglit test and came to the same conclusion. (I
will put that up for review shortly.)
I don't know why you'd ever want that, though (ieee fmin/fmax also
should return non-nan).

My guess is that DX9-level hardware had that behavior by virtue of just 
not caring about NaN at all, and the hardware folks were just being 
conservative in adding a new opcode rather than changing the behavior of 
the old one. I don't think GCN has the old-style min/max.

Cheers,
Nicolai


Roland



Jan

  but (as required by dx10)
the dx10 versions should pick a non-nan source over a nan source.
Other drivers presumably do the same (radeonsi, llvmpipe).
This was shown to make some difference for bug 103544, albeit it is not
required to fix it.
---
  src/gallium/drivers/r600/r600_shader.c  | 12 ++++++------
  src/gallium/drivers/r600/sb/sb_expr.cpp |  2 ++
  2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/src/gallium/drivers/r600/r600_shader.c 
b/src/gallium/drivers/r600/r600_shader.c
index 188fbc9d47..6a755bb3fd 100644
--- a/src/gallium/drivers/r600/r600_shader.c
+++ b/src/gallium/drivers/r600/r600_shader.c
@@ -8844,8 +8844,8 @@ static const struct r600_shader_tgsi_instruction 
r600_shader_tgsi_instruction[]
        [TGSI_OPCODE_DP3]       = { ALU_OP2_DOT4_IEEE, tgsi_dp},
        [TGSI_OPCODE_DP4]       = { ALU_OP2_DOT4_IEEE, tgsi_dp},
        [TGSI_OPCODE_DST]       = { ALU_OP0_NOP, tgsi_opdst},
-       [TGSI_OPCODE_MIN]       = { ALU_OP2_MIN, tgsi_op2},
-       [TGSI_OPCODE_MAX]       = { ALU_OP2_MAX, tgsi_op2},
+       [TGSI_OPCODE_MIN]       = { ALU_OP2_MIN_DX10, tgsi_op2},
+       [TGSI_OPCODE_MAX]       = { ALU_OP2_MAX_DX10, tgsi_op2},
        [TGSI_OPCODE_SLT]       = { ALU_OP2_SETGT, tgsi_op2_swap},
        [TGSI_OPCODE_SGE]       = { ALU_OP2_SETGE, tgsi_op2},
        [TGSI_OPCODE_MAD]       = { ALU_OP3_MULADD_IEEE, tgsi_op3},
@@ -9042,8 +9042,8 @@ static const struct r600_shader_tgsi_instruction 
eg_shader_tgsi_instruction[] =
        [TGSI_OPCODE_DP3]       = { ALU_OP2_DOT4_IEEE, tgsi_dp},
        [TGSI_OPCODE_DP4]       = { ALU_OP2_DOT4_IEEE, tgsi_dp},
        [TGSI_OPCODE_DST]       = { ALU_OP0_NOP, tgsi_opdst},
-       [TGSI_OPCODE_MIN]       = { ALU_OP2_MIN, tgsi_op2},
-       [TGSI_OPCODE_MAX]       = { ALU_OP2_MAX, tgsi_op2},
+       [TGSI_OPCODE_MIN]       = { ALU_OP2_MIN_DX10, tgsi_op2},
+       [TGSI_OPCODE_MAX]       = { ALU_OP2_MAX_DX10, tgsi_op2},
        [TGSI_OPCODE_SLT]       = { ALU_OP2_SETGT, tgsi_op2_swap},
        [TGSI_OPCODE_SGE]       = { ALU_OP2_SETGE, tgsi_op2},
        [TGSI_OPCODE_MAD]       = { ALU_OP3_MULADD_IEEE, tgsi_op3},
@@ -9265,8 +9265,8 @@ static const struct r600_shader_tgsi_instruction 
cm_shader_tgsi_instruction[] =
        [TGSI_OPCODE_DP3]       = { ALU_OP2_DOT4_IEEE, tgsi_dp},
        [TGSI_OPCODE_DP4]       = { ALU_OP2_DOT4_IEEE, tgsi_dp},
        [TGSI_OPCODE_DST]       = { ALU_OP0_NOP, tgsi_opdst},
-       [TGSI_OPCODE_MIN]       = { ALU_OP2_MIN, tgsi_op2},
-       [TGSI_OPCODE_MAX]       = { ALU_OP2_MAX, tgsi_op2},
+       [TGSI_OPCODE_MIN]       = { ALU_OP2_MIN_DX10, tgsi_op2},
+       [TGSI_OPCODE_MAX]       = { ALU_OP2_MAX_DX10, tgsi_op2},
        [TGSI_OPCODE_SLT]       = { ALU_OP2_SETGT, tgsi_op2_swap},
        [TGSI_OPCODE_SGE]       = { ALU_OP2_SETGE, tgsi_op2},
        [TGSI_OPCODE_MAD]       = { ALU_OP3_MULADD_IEEE, tgsi_op3},
diff --git a/src/gallium/drivers/r600/sb/sb_expr.cpp 
b/src/gallium/drivers/r600/sb/sb_expr.cpp
index 3dd3a4815b..7a5d62c8e8 100644
--- a/src/gallium/drivers/r600/sb/sb_expr.cpp
+++ b/src/gallium/drivers/r600/sb/sb_expr.cpp
@@ -753,7 +753,9 @@ bool expr_handler::fold_alu_op2(alu_node& n) {
                                n.bc.src[0].abs == n.bc.src[1].abs) {
                        switch (n.bc.op) {
                        case ALU_OP2_MIN: // (MIN x, x) => (MOV x)
+                       case ALU_OP2_MIN_DX10:
                        case ALU_OP2_MAX:
+                       case ALU_OP2_MAX_DX10:
                                convert_to_mov(n, v0, n.bc.src[0].neg, 
n.bc.src[0].abs);
                                return fold_alu_op1(n);
                        case ALU_OP2_ADD:  // (ADD x, x) => (MUL x, 2)

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