Mesa (master): compiler/nir: add lowering for 16-bit ldexp

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Module: Mesa
Branch: master
Commit: 763c8aabed3e03a67b6c7ba1388aa72f5b6044e4
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=763c8aabed3e03a67b6c7ba1388aa72f5b6044e4

Author: Iago Toral Quiroga <itoral at igalia.com>
Date:   Thu May 24 09:54:45 2018 +0200

compiler/nir: add lowering for 16-bit ldexp

v2 (Topi):
 - Make bit-size handling order be 16-bit, 32-bit, 64-bit
 - Clamp lower exponent range at -28 instead of -30.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen at intel.com>
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>

---

 src/compiler/nir/nir_opt_algebraic.py | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/compiler/nir/nir_opt_algebraic.py b/src/compiler/nir/nir_opt_algebraic.py
index 78e273d0e64..5f6ae5eeccc 100644
--- a/src/compiler/nir/nir_opt_algebraic.py
+++ b/src/compiler/nir/nir_opt_algebraic.py
@@ -851,7 +851,9 @@ for x, y in itertools.product(['f', 'u', 'i'], ['f', 'u', 'i']):
 
 def fexp2i(exp, bits):
    # We assume that exp is already in the right range.
-   if bits == 32:
+   if bits == 16:
+      return ('i2i16', ('ishl', ('iadd', exp, 15), 10))
+   elif bits == 32:
       return ('ishl', ('iadd', exp, 127), 23)
    elif bits == 64:
       return ('pack_64_2x32_split', 0, ('ishl', ('iadd', exp, 1023), 20))
@@ -869,7 +871,9 @@ def ldexp(f, exp, bits):
    # handles a range on exp of [-252, 254] which allows you to create any
    # value (including denorms if the hardware supports it) and to adjust the
    # exponent of any normal value to anything you want.
-   if bits == 32:
+   if bits == 16:
+      exp = ('imin', ('imax', exp, -28), 30)
+   elif bits == 32:
       exp = ('imin', ('imax', exp, -252), 254)
    elif bits == 64:
       exp = ('imin', ('imax', exp, -2044), 2046)
@@ -889,6 +893,7 @@ def ldexp(f, exp, bits):
    return ('fmul', ('fmul', f, pow2_1), pow2_2)
 
 optimizations += [
+   (('ldexp at 16', 'x', 'exp'), ldexp('x', 'exp', 16), 'options->lower_ldexp'),
    (('ldexp at 32', 'x', 'exp'), ldexp('x', 'exp', 32), 'options->lower_ldexp'),
    (('ldexp at 64', 'x', 'exp'), ldexp('x', 'exp', 64), 'options->lower_ldexp'),
 ]