Mesa (main): pan/bi: Use padding bytes for checking whether to stop disassembly

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Module: Mesa
Branch: main
Commit: 1acc3394c434891233cb67fd587f6cbbf2677514
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=1acc3394c434891233cb67fd587f6cbbf2677514

Author: Icecream95 <ixn at disroot.org>
Date:   Sat Jul 31 12:27:43 2021 +1200

pan/bi: Use padding bytes for checking whether to stop disassembly

Both Panfrost and the DDK add padding zero bytes to the end of
shaders, so we can use this instead of the end-of-shader clause for
checking whether to stop disassembling.

Shaders can have end-of-shader clauses partway through; these shaders
will now be completely disassembled instead of cut off at the first
end-of-shader clause.

A tag byte of zero is an invalid encoding, so unlike the previous
version of this test only check the first word.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12153>

---

 src/panfrost/bifrost/disassemble.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/panfrost/bifrost/disassemble.c b/src/panfrost/bifrost/disassemble.c
index 392974e7567..3fb9c8286da 100644
--- a/src/panfrost/bifrost/disassemble.c
+++ b/src/panfrost/bifrost/disassemble.c
@@ -439,7 +439,7 @@ decode_M(enum bi_constmod *mod, unsigned M1, unsigned M2, bool single)
         }
 }
 
-static bool dump_clause(FILE *fp, uint32_t *words, unsigned *size, unsigned offset, bool verbose)
+static void dump_clause(FILE *fp, uint32_t *words, unsigned *size, unsigned offset, bool verbose)
 {
         // State for a decoded clause
         struct bifrost_alu_inst instrs[8] = {};
@@ -447,7 +447,6 @@ static bool dump_clause(FILE *fp, uint32_t *words, unsigned *size, unsigned offs
         unsigned num_instrs = 0;
         unsigned num_consts = 0;
         uint64_t header_bits = 0;
-        bool stopbit = false;
 
         unsigned i;
         for (i = 0; ; i++, words += 4) {
@@ -648,8 +647,6 @@ static bool dump_clause(FILE *fp, uint32_t *words, unsigned *size, unsigned offs
         struct bifrost_header header;
         memcpy((char *) &header, (char *) &header_bits, sizeof(struct bifrost_header));
         dump_header(fp, header, verbose);
-        if (header.flow_control == BIFROST_FLOW_END)
-                stopbit = true;
 
         fprintf(fp, "{\n");
         for (i = 0; i < num_instrs; i++) {
@@ -687,7 +684,7 @@ static bool dump_clause(FILE *fp, uint32_t *words, unsigned *size, unsigned offs
         }
 
         fprintf(fp, "\n");
-        return stopbit;
+        return;
 }
 
 void disassemble_bifrost(FILE *fp, uint8_t *code, size_t size, bool verbose)
@@ -697,11 +694,15 @@ void disassemble_bifrost(FILE *fp, uint8_t *code, size_t size, bool verbose)
         // used for displaying branch targets
         unsigned offset = 0;
         while (words != words_end) {
+                /* Shaders have zero bytes at the end for padding; stop
+                 * disassembling when we hit them. */
+                if (*words == 0)
+                        break;
+
                 fprintf(fp, "clause_%d:\n", offset);
-                unsigned size;
 
-                if (dump_clause(fp, words, &size, offset, verbose))
-                        break;
+                unsigned size;
+                dump_clause(fp, words, &size, offset, verbose);
 
                 words += size * 4;
                 offset += size;