Mesa (master): v3d: Add a note for a potential performance win on multop/umul24.

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Module: Mesa
Branch: master
Commit: f9bdce99668b62da6ae34e584cfea6f47b402687
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=f9bdce99668b62da6ae34e584cfea6f47b402687

Author: Eric Anholt <eric at anholt.net>
Date:   Wed Dec 26 12:54:58 2018 -0800

v3d: Add a note for a potential performance win on multop/umul24.

Noticed while debugging a testcase.

---

 src/broadcom/compiler/vir_to_qpu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/broadcom/compiler/vir_to_qpu.c b/src/broadcom/compiler/vir_to_qpu.c
index 60d39063d5..c66bb84b3f 100644
--- a/src/broadcom/compiler/vir_to_qpu.c
+++ b/src/broadcom/compiler/vir_to_qpu.c
@@ -241,6 +241,10 @@ v3d_generate_code_block(struct v3d_compile *c,
                                 src[i] = temp_registers[index];
                                 break;
                         case QFILE_UNIF:
+                                /* XXX perf: If the last ldunif we emitted was
+                                 * the same uniform value, skip it.  Common
+                                 * for multop/umul24 sequences.
+                                 */
                                 if (!emitted_ldunif) {
                                         new_ldunif_instr(qinst, i);
                                         c->num_uniforms++;