KonstantinSeurer
/
mesa
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

vtn: Make tanh implementation even stupider 

The dEQP "precision" test tries to verify that the reference functions

   float sinh(float a) { return ((exp(a) - exp(-a)) / 2); }
   float cosh(float a) { return ((exp(a) + exp(-a)) / 2); }
   float tanh(float a) { return (sinh(a) / cosh(a)); }

produce the same values as the built-ins.  We simplified away the
multiplication by 0.5 in the numerator and denominator, and apparently
this causes them not to match for exactly 1 out of 13,632 values.

So, put it back in, fixing the test, but making our code generation
(and precision?) worse.
This commit is contained in:
Kenneth Graunke 2016-01-27 15:31:53 -08:00
parent 8f0ef9bbeb
commit 32e4c5ae30
1 changed files with 7 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
src/glsl/nir/spirv/vtn_glsl450.c
View File

@ -545,12 +545,14 @@ handle_glsl450_alu(struct vtn_builder *b, enum GLSLstd450 entrypoint,
return;
case GLSLstd450Tanh:
/* (e^x - e^(-x)) / (e^x + e^(-x)) */
/* (0.5 * (e^x - e^(-x))) / (0.5 * (e^x + e^(-x))) */
val->ssa->def =
nir_fdiv(nb, nir_fsub(nb, build_exp(nb, src[0]),
build_exp(nb, nir_fneg(nb, src[0]))),
nir_fadd(nb, build_exp(nb, src[0]),
build_exp(nb, nir_fneg(nb, src[0]))));
nir_fdiv(nb, nir_fmul(nb, nir_imm_float(nb, 0.5f),
nir_fsub(nb, build_exp(nb, src[0]),
build_exp(nb, nir_fneg(nb, src[0])))),
nir_fmul(nb, nir_imm_float(nb, 0.5f),
nir_fadd(nb, build_exp(nb, src[0]),
build_exp(nb, nir_fneg(nb, src[0])))));
return;
case GLSLstd450Asinh: