[Mesa-dev] [PATCH 4/6] panfrost/midgard: Add shifting int modifiers

[Alyssa Rosenzweig]

As a source modifier, shift allows shifting a value left by the bit
size, useful in conjunction with a greater register mode, for instance
to implement `upsample`. As a concrete example, the following OpenCL:

   ushort hr0 = /* ... */, uint r1 = /* ... */;
   uint r2 = (convert_uint(hr0) << 16) ^ b;

compiles to the following Midgard assembly:

   ixor r, (hr0) << 16, b

In reverse, the ".hi" output modifier shifts the value right by the bit
size, leaving just the carry/overflow at the bottom. To implement *_hi
functions in OpenCL (for <64-bit), we do arithmetic in the 2x higher
mode with the .hi modifier. (For 64-bit, things are hairier, since there
is not an 128-bit int mode).

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
---
 .../drivers/panfrost/midgard/disassemble.c    | 28 ++++++++-----------
 .../drivers/panfrost/midgard/midgard.h        |  4 +--
 2 files changed, 14 insertions(+), 18 deletions(-)

diff --git a/src/gallium/drivers/panfrost/midgard/disassemble.c b/src/gallium/drivers/panfrost/midgard/disassemble.c
index 1a25d0565f4..a92fbf174cc 100644
--- a/src/gallium/drivers/panfrost/midgard/disassemble.c
+++ b/src/gallium/drivers/panfrost/midgard/disassemble.c
@@ -118,7 +118,14 @@ static char *outmod_names_int[4] = {
         ".isat",
         ".usat",
         "",
-        ".unk3"
+        ".hi"
+};
+
+static char *srcmod_names_int[4] = {
+        "sext(",
+        "zext(",
+        "",
+        "("
 };
 
 static void
@@ -151,20 +158,7 @@ print_vector_src(unsigned src_binary, bool out_high,
         midgard_int_mod int_mod = src->mod;
 
         if (is_int) {
-                switch (int_mod) {
-                        case midgard_int_sign_extend:
-                                printf("sext(");
-                                break;
-                        case midgard_int_zero_extend:
-                                printf("zext(");
-                                break;
-                        case midgard_int_reserved:
-                                printf("unk(");
-                                break;
-                        case midgard_int_normal:
-                                /* Implicit */
-                                break;
-                }
+                printf("%s", srcmod_names_int[int_mod]);
         } else {
                 if (src->mod & MIDGARD_FLOAT_MOD_NEG)
                         printf("-");
@@ -259,7 +253,9 @@ print_vector_src(unsigned src_binary, bool out_high,
 
         /* Since we wrapped with a function-looking thing */
 
-        if ((is_int && (int_mod != midgard_int_normal))
+        if (is_int && int_mod == midgard_int_shift)
+                printf(") << %d", bits);
+        else if ((is_int && (int_mod != midgard_int_normal))
                         || (!is_int && src->mod & MIDGARD_FLOAT_MOD_ABS))
                 printf(")");
 }
diff --git a/src/gallium/drivers/panfrost/midgard/midgard.h b/src/gallium/drivers/panfrost/midgard/midgard.h
index b4eb788f813..9038644c684 100644
--- a/src/gallium/drivers/panfrost/midgard/midgard.h
+++ b/src/gallium/drivers/panfrost/midgard/midgard.h
@@ -195,7 +195,7 @@ typedef enum {
         midgard_outmod_int_saturate = 0,
         midgard_outmod_uint_saturate = 1,
         midgard_outmod_int_wrap = 2,
-        /* 0x3 unknown */
+        midgard_outmod_int_high = 3, /* Overflowed portion */
 } midgard_outmod_int;
 
 typedef enum {
@@ -215,7 +215,7 @@ typedef enum {
         midgard_int_sign_extend = 0,
         midgard_int_zero_extend = 1,
         midgard_int_normal = 2,
-        midgard_int_reserved = 3
+        midgard_int_shift = 3
 } midgard_int_mod;
 
 #define MIDGARD_FLOAT_MOD_ABS (1 << 0)
-- 
2.20.1