gallium: add FBFETCH opcode to retrieve the current sample value

Signed-off-by: Ilia Mirkin <[email protected]>
Reviewed-by: Nicolai Hähnle <[email protected]>

3 files changed, 15 insertions, 2 deletions

diff --git a/src/gallium/auxiliary/tgsi/tgsi_info.c b/src/gallium/auxiliary/tgsi/tgsi_info.c
index 3bec56119b8..4509b955c17 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_info.c
+++ b/src/gallium/auxiliary/tgsi/tgsi_info.c
@@ -106,7 +106,7 @@ static const struct tgsi_opcode_info opcode_info[TGSI_OPCODE_LAST] =
    { 1, 3, 0, 0, 0, 0, 0, COMP, "CMP", TGSI_OPCODE_CMP },
    { 1, 1, 0, 0, 0, 0, 0, CHAN, "SCS", TGSI_OPCODE_SCS },
    { 1, 2, 1, 0, 0, 0, 0, OTHR, "TXB", TGSI_OPCODE_TXB },
-   { 0, 1, 0, 0, 0, 0, 1, NONE, "", 69 },      /* removed */
+   { 1, 1, 0, 0, 0, 0, 0, OTHR, "FBFETCH", TGSI_OPCODE_FBFETCH },
    { 1, 2, 0, 0, 0, 0, 0, COMP, "DIV", TGSI_OPCODE_DIV },
    { 1, 2, 0, 0, 0, 0, 0, REPL, "DP2", TGSI_OPCODE_DP2 },
    { 1, 2, 1, 0, 0, 0, 0, OTHR, "TXL", TGSI_OPCODE_TXL },
diff --git a/src/gallium/docs/source/tgsi.rst b/src/gallium/docs/source/tgsi.rst
index 3e2d0e9fac2..b981278821c 100644
--- a/src/gallium/docs/source/tgsi.rst
+++ b/src/gallium/docs/source/tgsi.rst
@@ -2570,6 +2570,19 @@ Resource Access Opcodes
   image, while .w will contain the number of samples for multi-sampled
   images.
 
+.. opcode:: FBFETCH - Load data from framebuffer
+
+  Syntax: ``FBFETCH dst, output``
+
+  Example: ``FBFETCH TEMP[0], OUT[0]``
+
+  This is only valid on ``COLOR`` semantic outputs. Returns the color
+  of the current position in the framebuffer from before this fragment
+  shader invocation. May return the same value from multiple calls for
+  a particular output within a single invocation. Note that result may
+  be undefined if a fragment is drawn multiple times without a blend
+  barrier in between.
+
 
 .. _threadsyncopcodes:
 
diff --git a/src/gallium/include/pipe/p_shader_tokens.h b/src/gallium/include/pipe/p_shader_tokens.h
index a867d139144..b2d440a0b91 100644
--- a/src/gallium/include/pipe/p_shader_tokens.h
+++ b/src/gallium/include/pipe/p_shader_tokens.h
@@ -397,7 +397,7 @@ struct tgsi_property_data {
 #define TGSI_OPCODE_CMP                 66
 #define TGSI_OPCODE_SCS                 67
 #define TGSI_OPCODE_TXB                 68
-                                /* gap */
+#define TGSI_OPCODE_FBFETCH             69
 #define TGSI_OPCODE_DIV                 70
 #define TGSI_OPCODE_DP2                 71
 #define TGSI_OPCODE_TXL                 72