i965: Add a NIR analysis pass for determining when a boolean resolve is needed

v2: Fix the spelling of analyze and re-arrange code for better readability
    as per Connor's comments.
v3: Make the naming of things more consistent and add a pile of comments
v4: Stop trying to avoid vectors

Reviewed-by: Matt Turner <[email protected]>
Reviewed-by: Connor Abbott <[email protected]>

1 files changed, 78 insertions, 0 deletions

diff --git a/src/mesa/drivers/dri/i965/brw_nir.h b/src/mesa/drivers/dri/i965/brw_nir.h
new file mode 100644
index 00000000000..27782a3c807
--- /dev/null
+++ b/src/mesa/drivers/dri/i965/brw_nir.h
@@ -0,0 +1,78 @@
+/*
+ * Copyright © 2015 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.
+ */
+
+#pragma once
+
+#include "glsl/nir/nir.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Flags set in the instr->pass_flags field by i965 analysis passes */
+enum {
+   BRW_NIR_NON_BOOLEAN           = 0x0,
+
+   /* Indicates that the given instruction's destination is a boolean
+    * value but that it needs to be resolved before it can be used.
+    * On Gen <= 5, CMP instructions return a 32-bit value where the bottom
+    * bit represents the actual true/false value of the compare and the top
+    * 31 bits are undefined.  In order to use this value, we have to do a
+    * "resolve" operation by replacing the value of the CMP with -(x & 1)
+    * to sign-extend the bottom bit to 0/~0.
+    */
+   BRW_NIR_BOOLEAN_NEEDS_RESOLVE = 0x1,
+
+   /* Indicates that the given instruction's destination is a boolean
+    * value that has intentionally been left unresolved.  Not all boolean
+    * values need to be resolved immediately.  For instance, if we have
+    *
+    *    CMP r1 r2 r3
+    *    CMP r4 r5 r6
+    *    AND r7 r1 r4
+    *
+    * We don't have to resolve the result of the two CMP instructions
+    * immediately because the AND still does an AND of the bottom bits.
+    * Instead, we can save ourselves instructions by delaying the resolve
+    * until after the AND.  The result of the two CMP instructions is left
+    * as BRW_NIR_BOOLEAN_UNRESOLVED.
+    */
+   BRW_NIR_BOOLEAN_UNRESOLVED    = 0x2,
+
+   /* Indicates a that the given instruction's destination is a boolean
+    * value that does not need a resolve.  For instance, if you AND two
+    * values that are BRW_NIR_BOOLEAN_NEEDS_RESOLVE then we know that both
+    * values will be 0/~0 before we get them and the result of the AND is
+    * also guaranteed to be 0/~0 and does not need a resolve.
+    */
+   BRW_NIR_BOOLEAN_NO_RESOLVE    = 0x3,
+
+   /* A mask to mask the boolean status values off of instr->pass_flags */
+   BRW_NIR_BOOLEAN_MASK          = 0x3,
+};
+
+void brw_nir_analyze_boolean_resolves(nir_shader *nir);
+
+#ifdef __cplusplus
+}
+#endif