nir: Conditionalize the POW reconstruction on shader compiler options.

Mesa has a shader compiler struct flagging whether GLSL IR's opt_algebraic
and other passes should try and generate certain types of opcodes or
patterns.  Extend that to NIR by defining our own struct, which is
automatically generated from the Mesa struct in glsl_to_nir and provided
directly by the driver in TGSI-to-NIR.

v2: Split out the previous two prep patches.
v3: Rebase to master (no TGSI->NIR present)

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org> (v2)

3 files changed, 6 insertions, 2 deletions

diff --git a/src/glsl/nir/glsl_to_nir.cpp b/src/glsl/nir/glsl_to_nir.cpp
index bc43a7563dc..544d0d93282 100644
--- a/src/glsl/nir/glsl_to_nir.cpp
+++ b/src/glsl/nir/glsl_to_nir.cpp
@@ -142,6 +142,9 @@ glsl_to_nir(exec_list *ir, _mesa_glsl_parse_state *state,
          nir_shader_compiler_options *new_options =
             rzalloc(ctx, nir_shader_compiler_options);
          options = gl_options->NirOptions = new_options;
+
+         if (gl_options->EmitNoPow)
+            new_options->lower_fpow = true;
       } else {
          options = gl_options->NirOptions;
       }
diff --git a/src/glsl/nir/nir.h b/src/glsl/nir/nir.h
index d5253c42c19..bcc51e88ac8 100644
--- a/src/glsl/nir/nir.h
+++ b/src/glsl/nir/nir.h
@@ -1327,6 +1327,7 @@ typedef struct nir_function {
                   exec_list_get_head(&(func)->overload_list), node)
 
 typedef struct nir_shader_compiler_options {
+   bool lower_fpow;
 } nir_shader_compiler_options;
 
 typedef struct nir_shader {
diff --git a/src/glsl/nir/nir_opt_algebraic.py b/src/glsl/nir/nir_opt_algebraic.py
index 83223f768cd..76917f53a46 100644
--- a/src/glsl/nir/nir_opt_algebraic.py
+++ b/src/glsl/nir/nir_opt_algebraic.py
@@ -118,8 +118,8 @@ optimizations = [
    (('fexp',  ('flog',  a)), a), # e^ln(a)  = a
    (('flog2', ('fexp2', a)), a), # lg2(2^a) = a
    (('flog',  ('fexp',  a)), a), # ln(e^a)  = a
-   (('fexp2', ('fmul', ('flog2', a), b)), ('fpow', a, b)), # 2^(lg2(a)*b) = a^b
-   (('fexp',  ('fmul', ('flog', a), b)),  ('fpow', a, b)), # e^(ln(a)*b) = a^b
+   (('fexp2', ('fmul', ('flog2', a), b)), ('fpow', a, b), '!options->lower_fpow'), # 2^(lg2(a)*b) = a^b
+   (('fexp',  ('fmul', ('flog', a), b)),  ('fpow', a, b), '!options->lower_fpow'), # e^(ln(a)*b) = a^b
    (('fpow', a, 1.0), a),
    (('fpow', a, 2.0), ('fmul', a, a)),
    (('fpow', 2.0, a), ('fexp2', a)),