Remove dynamic indexing of matrices and vectors in HLSL

Re-landing after fixing D3D9 specific issues.

HLSL doesn't support dynamic indexing of matrices and vectors, so replace
that with helper functions that unroll dynamic indexing into switch/case
and static indexing.

Both the indexed vector/matrix expression and the index may have side
effects, and these will be evaluated correctly. If necessary, index
expressions that have side effects will be written to a temporary
variable that will replace the index.

Besides dEQP tests, this change is tested by a WebGL 2 conformance test.

In the case that a dynamic index is out-of-range, the base ESSL 3.00 spec
allows undefined behavior. KHR_robust_buffer_access_behavior adds the
requirement that program termination should not occur and that
out-of-range reads must return either a value from the active program's
memory or zero, and out-of-range writes should only affect the active
program's memory or do nothing. This patch clamps out-of-range indices so
that either the first or last item of the matrix/vector is accessed.

The code is not transformed in case the it fits within the limited subset
of ESSL 1.00 given in Appendix A of the spec. If the code isn't within
the restricted subset, even ESSL 1.00 shaders may require this
workaround.

BUG=angleproject:1116
TEST=dEQP-GLES3.functional.shaders.indexing.* (all pass after change)
     WebGL 2 conformance tests (glsl3/vector-dynamic-indexing.html)

Change-Id: I66a5e5a8d7f4267da0045f1cc2ba6b0dc7eb3f5d
Reviewed-on: https://chromium-review.googlesource.com/296671
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tryjob-Request: Jamie Madill <jmadill@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
diff --git a/src/compiler/translator/IntermTraverse.cpp b/src/compiler/translator/IntermTraverse.cpp
index f07a3e0..269a19b 100644
--- a/src/compiler/translator/IntermTraverse.cpp
+++ b/src/compiler/translator/IntermTraverse.cpp
@@ -81,8 +81,16 @@
 
 void TIntermTraverser::insertStatementsInParentBlock(const TIntermSequence &insertions)
 {
+    TIntermSequence emptyInsertionsAfter;
+    insertStatementsInParentBlock(insertions, emptyInsertionsAfter);
+}
+
+void TIntermTraverser::insertStatementsInParentBlock(const TIntermSequence &insertionsBefore,
+                                                     const TIntermSequence &insertionsAfter)
+{
     ASSERT(!mParentBlockStack.empty());
-    NodeInsertMultipleEntry insert(mParentBlockStack.back().node, mParentBlockStack.back().pos, insertions);
+    NodeInsertMultipleEntry insert(mParentBlockStack.back().node, mParentBlockStack.back().pos,
+                                   insertionsBefore, insertionsAfter);
     mInsertions.push_back(insert);
 }