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

[Matt Turner]

Module: Mesa
Branch: master
Commit: c15a407eb49d3b26bdbf039816636adb184c276a
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=c15a407eb49d3b26bdbf039816636adb184c276a

Author: Matt Turner <mattst88 at gmail.com>
Date:   Mon Nov  2 10:29:45 2015 -0800

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

This partially reverts commit bbf8239f92ecd79431dfa41402e1c85318e7267f.

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 at collabora.co.uk>
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

---

 src/mesa/drivers/dri/i965/brw_clip_util.c |    5 +++-
 src/mesa/drivers/dri/i965/brw_reg.h       |   38 ++++++-----------------------
 2 files changed, 11 insertions(+), 32 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_clip_util.c b/src/mesa/drivers/dri/i965/brw_clip_util.c
index 40ad144..73ba85e 100644
--- a/src/mesa/drivers/dri/i965/brw_clip_util.c
+++ b/src/mesa/drivers/dri/i965/brw_clip_util.c
@@ -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. */
diff --git a/src/mesa/drivers/dri/i965/brw_reg.h b/src/mesa/drivers/dri/i965/brw_reg.h
index 3da83b4..e34e7ea 100644
--- a/src/mesa/drivers/dri/i965/brw_reg.h
+++ b/src/mesa/drivers/dri/i965/brw_reg.h
@@ -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;
 }