fix: calculatenormal needs fliphandedness (#1783)

* Have OSL indicate when it needs fliphandedness in shader globals.

* Add testsuite test to check that calculatenormal() triggers a globals_needed flipHandedness value.

---------

Signed-off-by: Stephen Friedman <sfriedma@pixar.com>

src/liboslexec/runtimeoptimize.cpp

@@ -42,6 +42,8 @@ static ustring u_setmessage("setmessage");
 static ustring u_getmessage("getmessage");
 static ustring u_getattribute("getattribute");
 static ustring u_backfacing("backfacing");
+static ustring u_calculatenormal("calculatenormal");
+static ustring u_flipHandedness("flipHandedness");
 static ustring u_N("N");
 static ustring u_I("I");
 
@@ -3352,6 +3354,8 @@ RuntimeOptimizer::run()
             } else if (op.opname() == u_backfacing) {
                 m_globals_needed.insert(u_N);
                 m_globals_needed.insert(u_I);
+            } else if (op.opname() == u_calculatenormal) {
+                m_globals_needed.insert(u_flipHandedness);
             } else if (op.opname() == u_getattribute) {
                 Symbol* sym1 = opargsym(op, 1);
                 OSL_DASSERT(sym1 && sym1->typespec().is_string());

testsuite/globals-needed/printcalculatenormal.osl

@@ -0,0 +1,9 @@
+// Copyright Contributors to the Open Shading Language project.
+// SPDX-License-Identifier: BSD-3-Clause
+// https://github.com/AcademySoftwareFoundation/OpenShadingLanguage
+
+shader printcalculatenormal ()
+{
+    normal n2 = calculatenormal(P+1);
+    printf ("calculatenormal = %f", n2);
+}

testsuite/globals-needed/ref/out.txt

@@ -1 +1,2 @@
 Need 2 globals:  I N
+Need 2 globals:  P flipHandedness

testsuite/globals-needed/run.py

@@ -5,6 +5,7 @@
 # https://github.com/AcademySoftwareFoundation/OpenShadingLanguage
 
 command += testshade("-g 2 2 -debug printbackfacing")
+command += testshade("-g 2 2 -debug printcalculatenormal")
 
 # debug output is very verbose, use regexp to filter down to
 # only the line we're interested in testing