[Mesa-dev] [PATCH] tgsi/scan: use wrap-around shift behavior explicitly for file_mask

[sroland at vmware.com]

From: Roland Scheidegger <sroland at vmware.com>

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).
---
 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 c35eff2..0d229c9 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] |= (1 << (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 603fd84..48c004c 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] & (1 << (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 e5fb679..fa1c0b8 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] & (1 << (i & 31))) {
             const struct pipe_sampler_view *view =
                ctx->sampler_views[shader_type][i];
             lp_sampler_static_texture_state(
-- 
2.7.4