11 files changed, 34 insertions, 1 deletions
diff --git a/src/compiler/glsl/ast_to_hir.cpp b/src/compiler/glsl/ast_to_hir.cpp
index 0cfce6893ee..8ddc084cab7 100644
--- a/src/compiler/glsl/ast_to_hir.cpp
+++ b/src/compiler/glsl/ast_to_hir.cpp
@@ -4697,6 +4697,14 @@ ast_declarator_list::hir(exec_list *instructions,
       apply_layout_qualifier_to_variable(&this->type->qualifier, var, state,
                                          &loc);
 
+      if ((var->data.mode == ir_var_auto || var->data.mode == ir_var_temporary)
+          && (var->type->is_numeric() || var->type->is_boolean())
+          && state->zero_init) {
+         const ir_constant_data data = {0};
+         var->data.has_initializer = true;
+         var->constant_initializer = new(var) ir_constant(var->type, &data);
+      }
+
       if (this->type->qualifier.flags.q.invariant) {
          if (!is_varying_var(var, state->stage)) {
             _mesa_glsl_error(&loc, state,
diff --git a/src/compiler/glsl/glsl_parser_extras.cpp b/src/compiler/glsl/glsl_parser_extras.cpp
index fab64bbb87b..96014247e5d 100644
--- a/src/compiler/glsl/glsl_parser_extras.cpp
+++ b/src/compiler/glsl/glsl_parser_extras.cpp
@@ -74,6 +74,7 @@ _mesa_glsl_parse_state::_mesa_glsl_parse_state(struct gl_context *_ctx,
    /* Set default language version and extensions */
    this->language_version = 110;
    this->forced_language_version = ctx->Const.ForceGLSLVersion;
+   this->zero_init = ctx->Const.GLSLZeroInit;
    this->es_shader = false;
    this->ARB_texture_rectangle_enable = true;
 
diff --git a/src/compiler/glsl/glsl_parser_extras.h b/src/compiler/glsl/glsl_parser_extras.h
index 8c43292d8aa..669b3d1b201 100644
--- a/src/compiler/glsl/glsl_parser_extras.h
+++ b/src/compiler/glsl/glsl_parser_extras.h
@@ -306,6 +306,7 @@ struct _mesa_glsl_parse_state {
    bool es_shader;
    unsigned language_version;
    unsigned forced_language_version;
+   bool zero_init;
    gl_shader_stage stage;
 
    /**
diff --git a/src/gallium/include/state_tracker/st_api.h b/src/gallium/include/state_tracker/st_api.h
index 41daa47986c..21d5177aa2f 100644
--- a/src/gallium/include/state_tracker/st_api.h
+++ b/src/gallium/include/state_tracker/st_api.h
@@ -242,6 +242,7 @@ struct st_config_options
    unsigned force_glsl_version;
    boolean force_s3tc_enable;
    boolean allow_glsl_extension_directive_midshader;
+   boolean glsl_zero_init;
 };
 
 /**
diff --git a/src/gallium/state_trackers/dri/dri_screen.c b/src/gallium/state_trackers/dri/dri_screen.c
index 2ac55c88926..b16585a38cc 100644
--- a/src/gallium/state_trackers/dri/dri_screen.c
+++ b/src/gallium/state_trackers/dri/dri_screen.c
@@ -74,6 +74,7 @@ const __DRIconfigOptionsExtension gallium_config_options = {
 
       DRI_CONF_SECTION_MISCELLANEOUS
          DRI_CONF_ALWAYS_HAVE_DEPTH_BUFFER("false")
+         DRI_CONF_GLSL_ZERO_INIT("false")
       DRI_CONF_SECTION_END
    DRI_CONF_END
 };
@@ -98,6 +99,7 @@ dri_fill_st_options(struct st_config_options *options,
       driQueryOptionb(optionCache, "force_s3tc_enable");
    options->allow_glsl_extension_directive_midshader =
       driQueryOptionb(optionCache, "allow_glsl_extension_directive_midshader");
+   options->glsl_zero_init = driQueryOptionb(optionCache, "glsl_zero_init");
 }
 
 static const __DRIconfig **
diff --git a/src/mesa/drivers/dri/common/drirc b/src/mesa/drivers/dri/common/drirc
index 3912d8b8c7e..af84ee82e8a 100644
--- a/src/mesa/drivers/dri/common/drirc
+++ b/src/mesa/drivers/dri/common/drirc
@@ -96,5 +96,9 @@ TODO: document the other workarounds.
         <application name="Warsow (64-bit)" executable="warsow.x86_64">
             <option name="allow_glsl_extension_directive_midshader" value="true" />
         </application>
+
+        <application name="Rust" executable="rust">
+            <option name="glsl_zero_init" value="true"/>
+        </application>
     </device>
 </driconf>
diff --git a/src/mesa/drivers/dri/common/xmlpool/t_options.h b/src/mesa/drivers/dri/common/xmlpool/t_options.h
index 4b298a46112..341c3763dee 100644
--- a/src/mesa/drivers/dri/common/xmlpool/t_options.h
+++ b/src/mesa/drivers/dri/common/xmlpool/t_options.h
@@ -337,7 +337,10 @@ DRI_CONF_OPT_BEGIN_B(always_have_depth_buffer, def) \
         DRI_CONF_DESC(en,gettext("Create all visuals with a depth buffer")) \
 DRI_CONF_OPT_END
 
-
+#define DRI_CONF_GLSL_ZERO_INIT(def) \
+DRI_CONF_OPT_BEGIN_B(glsl_zero_init, def) \
+        DRI_CONF_DESC(en,gettext("Force uninitialized variables to default to zero")) \
+DRI_CONF_OPT_END
 
 /**
  * \brief Initialization configuration options
diff --git a/src/mesa/drivers/dri/i965/brw_context.c b/src/mesa/drivers/dri/i965/brw_context.c
index 5e3c9d169b3..3f0c2e3b483 100644
--- a/src/mesa/drivers/dri/i965/brw_context.c
+++ b/src/mesa/drivers/dri/i965/brw_context.c
@@ -827,6 +827,8 @@ brw_process_driconf_options(struct brw_context *brw)
    ctx->Const.AllowGLSLExtensionDirectiveMidShader =
       driQueryOptionb(options, "allow_glsl_extension_directive_midshader");
 
+   ctx->Const.GLSLZeroInit = driQueryOptionb(options, "glsl_zero_init");
+
    brw->dual_color_blend_by_location =
       driQueryOptionb(options, "dual_color_blend_by_location");
 }
diff --git a/src/mesa/drivers/dri/i965/intel_screen.c b/src/mesa/drivers/dri/i965/intel_screen.c
index 1c71e09e7ad..432ab7bdb63 100644
--- a/src/mesa/drivers/dri/i965/intel_screen.c
+++ b/src/mesa/drivers/dri/i965/intel_screen.c
@@ -88,6 +88,10 @@ DRI_CONF_BEGIN
 	 DRI_CONF_DESC(en, "Perform code generation at shader link time.")
       DRI_CONF_OPT_END
    DRI_CONF_SECTION_END
+
+   DRI_CONF_SECTION_MISCELLANEOUS
+      DRI_CONF_GLSL_ZERO_INIT("false")
+   DRI_CONF_SECTION_END
 DRI_CONF_END
 };
 
diff --git a/src/mesa/main/mtypes.h b/src/mesa/main/mtypes.h
index cab315df23d..29e47debfc2 100644
--- a/src/mesa/main/mtypes.h
+++ b/src/mesa/main/mtypes.h
@@ -3536,6 +3536,11 @@ struct gl_constants
    GLboolean AllowGLSLExtensionDirectiveMidShader;
 
    /**
+    * Force uninitialized variables to default to zero.
+    */
+   GLboolean GLSLZeroInit;
+
+   /**
     * Does the driver support real 32-bit integers?  (Otherwise, integers are
     * simulated via floats.)
     */
diff --git a/src/mesa/state_tracker/st_extensions.c b/src/mesa/state_tracker/st_extensions.c
index c5ecd5a2dd7..3d27ca3a905 100644
--- a/src/mesa/state_tracker/st_extensions.c
+++ b/src/mesa/state_tracker/st_extensions.c
@@ -925,6 +925,8 @@ void st_init_extensions(struct pipe_screen *screen,
       extensions->EXT_texture_integer = GL_FALSE;
    }
 
+   consts->GLSLZeroInit = options->glsl_zero_init;
+
    consts->UniformBooleanTrue = consts->NativeIntegers ? ~0U : fui(1.0f);
 
    /* Below are the cases which cannot be moved into tables easily. */