Mesa (master): intel/fs: work around gen12 lower-precision source modifier limitation

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Module: Mesa
Branch: master
Commit: cf52b40fb0bf53816ca4bb90e31ecd146fbcb533
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=cf52b40fb0bf53816ca4bb90e31ecd146fbcb533

Author: Mark Janes <markjanes at swizzler.org>
Date:   Fri Aug  7 13:11:08 2020 -0700

intel/fs: work around gen12 lower-precision source modifier limitation

GEN:BUG:1604601757 prevents source modifiers for multiplication of
lower precision integers.

lower_mul_dword_inst() splits 32x32 multiplication into 32x16, and
needs to eliminate source modifiers in this case.

Closes: #3329
Reviewed-by: Francisco Jerez <currojerez at riseup.net>

---

 src/intel/compiler/brw_fs.cpp | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/intel/compiler/brw_fs.cpp b/src/intel/compiler/brw_fs.cpp
index a89c53ea5a5..dbf7391baef 100644
--- a/src/intel/compiler/brw_fs.cpp
+++ b/src/intel/compiler/brw_fs.cpp
@@ -3930,7 +3930,20 @@ fs_visitor::lower_mul_dword_inst(fs_inst *inst, bblock_t *block)
       high.offset = inst->dst.offset % REG_SIZE;
 
       if (devinfo->gen >= 7) {
-         if (inst->src[1].abs)
+         /* From GEN:BUG:1604601757:
+          *
+          * "When multiplying a DW and any lower precision integer, source modifier
+          *  is not supported."
+          *
+          * An unsupported negate modifier on src[1] would ordinarily be
+          * lowered by the subsequent lower_regioning pass.  In this case that
+          * pass would spawn another dword multiply.  Instead, lower the
+          * modifier first.
+          */
+         const bool source_mods_unsupported = (devinfo->gen >= 12);
+
+         if (inst->src[1].abs || (inst->src[1].negate &&
+                                  source_mods_unsupported))
             lower_src_modifiers(this, block, inst, 1);
 
          if (inst->src[1].file == IMM) {