intel/compiler: Introduce simple IR analysis pass framework

Motivated in detail in the source code.  The only piece missing here
from the analysis pass infrastructure is some sort of mechanism to
broadcast changes in the IR to all existing analysis passes, which
will be addressed by a future commit.  The analysis_dependency_class
enum might seem a bit silly at this point, more interesting dependency
categories will be defined later on.

Reviewed-by: Matt Turner <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4012>

2 files changed, 147 insertions, 0 deletions

diff --git a/src/intel/compiler/brw_ir_analysis.h b/src/intel/compiler/brw_ir_analysis.h
new file mode 100644
index 00000000000..d2a984ab96b
--- /dev/null
+++ b/src/intel/compiler/brw_ir_analysis.h
@@ -0,0 +1,146 @@
+/* -*- c++ -*- */
+/*
+ * Copyright © 2016 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#ifndef BRW_IR_ANALYSIS_H
+#define BRW_IR_ANALYSIS_H
+
+namespace brw {
+   /**
+    * Bitset of state categories that can influence the result of IR analysis
+    * passes.
+    */
+   enum analysis_dependency_class {
+      /**
+       * The analysis doesn't depend on the IR, its result is effectively a
+       * constant during the compilation.
+       */
+      DEPENDENCY_NOTHING = 0,
+      /**
+       * The analysis depends on the program being literally the same (good
+       * luck...), any change in the input invalidates previous analysis
+       * computations.
+       */
+      DEPENDENCY_EVERYTHING = ~0
+   };
+
+   inline analysis_dependency_class
+   operator|(analysis_dependency_class x, analysis_dependency_class y)
+   {
+      return static_cast<analysis_dependency_class>(
+         static_cast<unsigned>(x) | static_cast<unsigned>(y));
+   }
+}
+
+/**
+ * Instantiate a program analysis class \p L which can calculate an object of
+ * type \p T as result.  \p C is a closure that encapsulates whatever
+ * information is required as argument to run the analysis pass.  The purpose
+ * of this class is to make sure that:
+ *
+ *  - The analysis pass is executed lazily whenever it's needed and multiple
+ *    executions are optimized out as long as the cached result remains marked
+ *    up-to-date.
+ *
+ *  - There is no way to access the cached analysis result without first
+ *    calling L::require(), which makes sure that the analysis pass is rerun
+ *    if necessary.
+ *
+ *  - The cached result doesn't become inconsistent with the program for as
+ *    long as it remains marked up-to-date. (This is only enforced in debug
+ *    builds for performance reasons)
+ *
+ * The requirements on \p T are the following:
+ *
+ *  - Constructible with a single argument, as in 'x = T(c)' for \p c of type
+ *    \p C.
+ *
+ *  - 'x.dependency_class()' on const \p x returns a bitset of
+ *    brw::analysis_dependency_class specifying the set of IR objects that are
+ *    required to remain invariant for the cached analysis result to be
+ *    considered valid.
+ *
+ *  - 'x.validate(c)' on const \p x returns a boolean result specifying
+ *    whether the analysis result \p x is consistent with the input IR.  This
+ *    is currently only used for validation in debug builds.
+ */
+#define BRW_ANALYSIS(L, T, C)                                           \
+   class L {                                                            \
+   public:                                                              \
+      /**                                                               \
+       * Construct a program analysis.  \p c is an arbitrary object     \
+       * passed as argument to the constructor of the analysis result   \
+       * object of type \p T.                                           \
+       */                                                               \
+      L(C const &c) : c(c), p(NULL) {}                                  \
+                                                                        \
+      /**                                                               \
+       * Destroy a program analysis.                                    \
+       */                                                               \
+      ~L()                                                              \
+      {                                                                 \
+         delete p;                                                      \
+      }                                                                 \
+                                                                        \
+      /**                                                               \
+       * Obtain the result of a program analysis.  This gives a         \
+       * guaranteed up-to-date result, the analysis pass will be        \
+       * rerun implicitly if it has become stale.                       \
+       */                                                               \
+      T &                                                               \
+      require()                                                         \
+      {                                                                 \
+         if (p)                                                         \
+            assert(p->validate(c));                                     \
+         else                                                           \
+            p = new T(c);                                               \
+                                                                        \
+         return *p;                                                     \
+      }                                                                 \
+                                                                        \
+      const T &                                                         \
+      require() const                                                   \
+      {                                                                 \
+         return const_cast<L *>(this)->require();                       \
+      }                                                                 \
+                                                                        \
+      /**                                                               \
+       * Report that dependencies of the analysis pass may have changed \
+       * since the last calculation and the cached analysis result may  \
+       * have to be discarded.                                          \
+       */                                                               \
+      void                                                              \
+      invalidate(brw::analysis_dependency_class c)                      \
+      {                                                                 \
+         if (p && c & p->dependency_class()) {                          \
+            delete p;                                                   \
+            p = NULL;                                                   \
+         }                                                              \
+      }                                                                 \
+                                                                        \
+   private:                                                             \
+      C c;                                                              \
+      T *p;                                                             \
+   }
+
+#endif
diff --git a/src/intel/compiler/meson.build b/src/intel/compiler/meson.build
index 2c44949c2b7..b110c0efeb3 100644
--- a/src/intel/compiler/meson.build
+++ b/src/intel/compiler/meson.build
@@ -70,6 +70,7 @@ libintel_compiler_files = files(
   'brw_interpolation_map.c',
   'brw_ir.h',
   'brw_ir_allocator.h',
+  'brw_ir_analysis.h',
   'brw_ir_fs.h',
   'brw_ir_vec4.h',
   'brw_nir.h',