[PATCH 1/1] vkd3d-shader/hlsl: Document some possibly obscure HLSL opcodes.

[Giovanni Mascellani]

From: Giovanni Mascellani

---
 libs/vkd3d-shader/hlsl.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/libs/vkd3d-shader/hlsl.h b/libs/vkd3d-shader/hlsl.h
index 04e681a9..1b5ae172 100644
--- a/libs/vkd3d-shader/hlsl.h
+++ b/libs/vkd3d-shader/hlsl.h
@@ -550,9 +550,16 @@ enum hlsl_ir_expr_op
     HLSL_OP2_NEQUAL,
     HLSL_OP2_RSHIFT,

+    /* DP2ADD(a, b, c) computes the scalar product of a.xy and b.xy,
+     * then adds c. */
     HLSL_OP3_DP2ADD,
+    /*  LERP(a, b, c) computes a * (1-z) + b * z or, equivalently,
+     *  a + z * (b - c). */
     HLSL_OP3_LERP,
-    /* TERNARY is used specifically for ternary operator, and later lowered according to profile to e.g. MOVC. */
+    /* MOVC(a, b, c) returns c is a is bitwise zero and b
+     * otherwise. TERNARY(a, b, c) returns c if a == 0 and y
+     * otherwise. They differ for floating point numbers, because
+     * -0.0 == 0.0, but it is not bitwise zero. */
     HLSL_OP3_MOVC,
     HLSL_OP3_TERNARY,
 };