mesa: Replace the EmitNoIfs compiler flag with a MaxIfDepth flag.

This is a better, more fine-grained way of lowering if statements.  Fixes the
game And Yet It Moves on nv50.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

src/mesa/drivers/dri/i915/i915_context.c

@@ -189,7 +189,7 @@ i915CreateContext(int api,
 
    struct gl_shader_compiler_options *const fs_options =
       & ctx->ShaderCompilerOptions[MESA_SHADER_FRAGMENT];
-   fs_options->EmitNoIfs = GL_TRUE;
+   fs_options->MaxIfDepth = 0;
    fs_options->EmitNoNoise = GL_TRUE;
    fs_options->EmitNoPow = GL_TRUE;
    fs_options->EmitNoMainReturn = GL_TRUE;

src/mesa/main/mtypes.h

@@ -2266,11 +2266,6 @@ struct gl_shader_compiler_options
    /** Driver-selectable options: */
    GLboolean EmitCondCodes;             /**< Use condition codes? */
    GLboolean EmitNVTempInitialization;  /**< 0-fill NV temp registers */
-   /**
-    * Attempts to flatten all ir_if (OPCODE_IF) for GPUs that can't
-    * support control flow.
-    */
-   GLboolean EmitNoIfs;
    GLboolean EmitNoLoops;
    GLboolean EmitNoFunctions;
    GLboolean EmitNoCont;                  /**< Emit CONT opcode? */
@@ -2288,6 +2283,7 @@ struct gl_shader_compiler_options
    GLboolean EmitNoIndirectUniform; /**< No indirect addressing of constants */
    /*@}*/
 
+   GLuint MaxIfDepth;               /**< Maximum nested IF blocks */
    GLuint MaxUnrollIterations;
 
    struct gl_sl_pragmas DefaultPragmas; /**< Default #pragma settings */

src/mesa/program/ir_to_mesa.cpp

@@ -3119,7 +3119,7 @@ get_mesa_program(struct gl_context *ctx,
 
       switch (mesa_inst->Opcode) {
       case OPCODE_IF:
-	 if (options->EmitNoIfs) {
+	 if (options->MaxIfDepth == 0) {
 	    linker_warning(shader_program,
 			   "Couldn't flatten if-statement.  "
 			   "This will likely result in software "
@@ -3241,10 +3241,10 @@ _mesa_ir_link_shader(struct gl_context *ctx, struct gl_shader_program *prog)
 
 	 progress = lower_quadop_vector(ir, true) || progress;
 
-	 if (options->EmitNoIfs) {
+	 if (options->MaxIfDepth == 0)
 	    progress = lower_discard(ir) || progress;
-	    progress = lower_if_to_cond_assign(ir) || progress;
-	 }
+
+	 progress = lower_if_to_cond_assign(ir, options->MaxIfDepth) || progress;
 
 	 if (options->EmitNoNoise)
 	    progress = lower_noise(ir) || progress;

src/mesa/state_tracker/st_extensions.c

@@ -173,7 +173,7 @@ void st_init_limits(struct st_context *st)
       options->EmitNoNoise = TRUE;
 
       /* TODO: make these more fine-grained if anyone needs it */
-      options->EmitNoIfs = !screen->get_shader_param(screen, sh, PIPE_SHADER_CAP_MAX_CONTROL_FLOW_DEPTH);
+      options->MaxIfDepth = screen->get_shader_param(screen, sh, PIPE_SHADER_CAP_MAX_CONTROL_FLOW_DEPTH);
       options->EmitNoLoops = !screen->get_shader_param(screen, sh, PIPE_SHADER_CAP_MAX_CONTROL_FLOW_DEPTH);
       options->EmitNoFunctions = !screen->get_shader_param(screen, sh, PIPE_SHADER_CAP_SUBROUTINES);
       options->EmitNoMainReturn = !screen->get_shader_param(screen, sh, PIPE_SHADER_CAP_SUBROUTINES);

src/mesa/state_tracker/st_glsl_to_tgsi.cpp

@@ -4991,10 +4991,10 @@ st_link_shader(struct gl_context *ctx, struct gl_shader_program *prog)
 
          progress = lower_quadop_vector(ir, false) || progress;
 
-         if (options->EmitNoIfs) {
+         if (options->MaxIfDepth == 0)
             progress = lower_discard(ir) || progress;
-            progress = lower_if_to_cond_assign(ir) || progress;
-         }
+
+         progress = lower_if_to_cond_assign(ir, options->MaxIfDepth) || progress;
 
          if (options->EmitNoNoise)
             progress = lower_noise(ir) || progress;