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i965: Make brw_imm_vf4() take 8-bit restricted floats.

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This partially reverts commit bbf8239f92.

I didn't like that commit to begin with -- computing things at compile
time is fine -- but for purposes of verifying that the resulting values
are correct, looking up 0x00 and 0x30 in a table is a lot better than
evaluating a recursive function.

Anyway, by making brw_imm_vf4() take the actual 8-bit restricted floats
directly (instead of only integral values that would be converted to
restricted float), we can use this function as a replacement for the
vector float src_reg/fs_reg constructors.

brw_float_to_vf() is not currently an inline function, so it will not be
evaluated at compile time. I'll address that in a follow-up patch.

Reviewed-by: Emil Velikov <emil.velikov@collabora.co.uk>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
This commit is contained in:
Matt Turner 2015-11-02 10:29:45 -08:00
parent e8c5ef3eca
commit c15a407eb4
2 changed files with 11 additions and 32 deletions
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5
src/mesa/drivers/dri/i965/brw_clip_util.c
View file

@ -224,7 +224,10 @@ void brw_clip_interp_vertex( struct brw_clip_compile *c,
vec1(t_nopersp),
brw_imm_f(0));
brw_IF(p, BRW_EXECUTE_1);
brw_MOV(p, t_nopersp, brw_imm_vf4(1, 0, 0, 0));
brw_MOV(p, t_nopersp, brw_imm_vf4(brw_float_to_vf(1.0),
brw_float_to_vf(0.0),
brw_float_to_vf(0.0),
brw_float_to_vf(0.0)));
brw_ENDIF(p);
/* Now compute t_nopersp = t_nopersp.y/t_nopersp.x and broadcast it. */

38
src/mesa/drivers/dri/i965/brw_reg.h
View file

@ -43,7 +43,6 @@
#define BRW_REG_H
#include <stdbool.h>
#include "main/imports.h"
#include "main/compiler.h"
#include "main/macros.h"
#include "program/prog_instruction.h"
@ -638,38 +637,15 @@ brw_imm_vf(unsigned v)
return imm;
}
/**
* Convert an integer into a "restricted" 8-bit float, used in vector
* immediates. The 8-bit floating point format has a sign bit, an
* excess-3 3-bit exponent, and a 4-bit mantissa. All integer values
* from -31 to 31 can be represented exactly.
*/
static inline uint8_t
int_to_float8(int x)
{
if (x == 0) {
return 0;
} else if (x < 0) {
return 1 << 7 | int_to_float8(-x);
} else {
const unsigned exponent = _mesa_logbase2(x);
const unsigned mantissa = (x - (1 << exponent)) << (4 - exponent);
assert(exponent <= 4);
return (exponent + 3) << 4 | mantissa;
}
}
/**
* Construct a floating-point packed vector immediate from its integer
* values. \sa int_to_float8()
*/
static inline struct brw_reg
brw_imm_vf4(int v0, int v1, int v2, int v3)
brw_imm_vf4(unsigned v0, unsigned v1, unsigned v2, unsigned v3)
{
return brw_imm_vf((int_to_float8(v0) << 0) |
(int_to_float8(v1) << 8) |
(int_to_float8(v2) << 16) |
(int_to_float8(v3) << 24));
struct brw_reg imm = brw_imm_reg(BRW_REGISTER_TYPE_VF);
imm.vstride = BRW_VERTICAL_STRIDE_0;
imm.width = BRW_WIDTH_4;
imm.hstride = BRW_HORIZONTAL_STRIDE_1;
imm.ud = ((v0 << 0) | (v1 << 8) | (v2 << 16) | (v3 << 24));
return imm;
}