Mesa (master): tgsi/scan: use wrap-around shift behavior explicitly for file_mask

[Roland Scheidegger]

Module: Mesa
Branch: master
Commit: 06e724c7b4ade29868531edb20900859f566a077
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=06e724c7b4ade29868531edb20900859f566a077

Author: Roland Scheidegger <sroland at vmware.com>
Date:   Fri Mar  2 03:00:41 2018 +0100

tgsi/scan: use wrap-around shift behavior explicitly for file_mask

The comment said it will only represent the lowest 32 regs. This was
not entirely true in practice, since at least on x86 you'll get
masked shifts (unless the compiler could recognize it already and toss
it out). It turns out this actually works out alright (presumably
noone uses it for temp regs) when increasing max sampler views, so
make that behavior explicit.
Albeit it feels a bit hacky (but in any case, explicit behavior there
is better than undefined behavior).

Reviewed-by: Jose Fonseca <jfonseca at vmware.com>
Reviewed-by: Brian Paul <brianp at vmware.com>

---

 src/gallium/auxiliary/tgsi/tgsi_scan.c     | 7 +++++--
 src/gallium/drivers/llvmpipe/lp_state_fs.c | 7 ++++++-
 src/gallium/drivers/swr/swr_shader.cpp     | 2 +-
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/gallium/auxiliary/tgsi/tgsi_scan.c b/src/gallium/auxiliary/tgsi/tgsi_scan.c
index c35eff25ba..4a2b354063 100644
--- a/src/gallium/auxiliary/tgsi/tgsi_scan.c
+++ b/src/gallium/auxiliary/tgsi/tgsi_scan.c
@@ -585,8 +585,11 @@ scan_declaration(struct tgsi_shader_info *info,
       int buffer;
       unsigned index, target, type;
 
-      /* only first 32 regs will appear in this bitfield */
-      info->file_mask[file] |= (1 << reg);
+      /*
+       * only first 32 regs will appear in this bitfield, if larger
+       * bits will wrap around.
+       */
+      info->file_mask[file] |= (1u << (reg & 31));
       info->file_count[file]++;
       info->file_max[file] = MAX2(info->file_max[file], (int)reg);
 
diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c b/src/gallium/drivers/llvmpipe/lp_state_fs.c
index 603fd84f6b..66645b07ac 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
@@ -3323,7 +3323,12 @@ make_variant_key(struct llvmpipe_context *lp,
    if (shader->info.base.file_max[TGSI_FILE_SAMPLER_VIEW] != -1) {
       key->nr_sampler_views = shader->info.base.file_max[TGSI_FILE_SAMPLER_VIEW] + 1;
       for(i = 0; i < key->nr_sampler_views; ++i) {
-         if(shader->info.base.file_mask[TGSI_FILE_SAMPLER_VIEW] & (1 << i)) {
+         /*
+          * Note sview may exceed what's representable by file_mask.
+          * This will still work, the only downside is that not actually
+          * used views may be included in the shader key.
+          */
+         if(shader->info.base.file_mask[TGSI_FILE_SAMPLER_VIEW] & (1u << (i & 31))) {
             lp_sampler_static_texture_state(&key->state[i].texture_state,
                                             lp->sampler_views[PIPE_SHADER_FRAGMENT][i]);
          }
diff --git a/src/gallium/drivers/swr/swr_shader.cpp b/src/gallium/drivers/swr/swr_shader.cpp
index e5fb679f8b..477fa7f2db 100644
--- a/src/gallium/drivers/swr/swr_shader.cpp
+++ b/src/gallium/drivers/swr/swr_shader.cpp
@@ -98,7 +98,7 @@ swr_generate_sampler_key(const struct lp_tgsi_info &info,
       key.nr_sampler_views =
          info.base.file_max[TGSI_FILE_SAMPLER_VIEW] + 1;
       for (unsigned i = 0; i < key.nr_sampler_views; i++) {
-         if (info.base.file_mask[TGSI_FILE_SAMPLER_VIEW] & (1 << i)) {
+         if (info.base.file_mask[TGSI_FILE_SAMPLER_VIEW] & (1u << (i & 31))) {
             const struct pipe_sampler_view *view =
                ctx->sampler_views[shader_type][i];
             lp_sampler_static_texture_state(