llvmpipe: switch to using dynamic stack allocation instead of registers

with mutable vars we don't need to follow the phi nodes. meaning that
control flow becomes trivial as we don't have scan the rest of the tgsi
to figure out the variable usage anymore. futhermore the memory2register
pass promotes alloca/store/load to registers while inserting the right phi
nodes. so we get simplicity and performance.

1 files changed, 6 insertions, 5 deletions

diff --git a/src/gallium/drivers/llvmpipe/lp_state_fs.c b/src/gallium/drivers/llvmpipe/lp_state_fs.c
index 320e2b72e4..2001a95661 100644
--- a/src/gallium/drivers/llvmpipe/lp_state_fs.c
+++ b/src/gallium/drivers/llvmpipe/lp_state_fs.c
@@ -468,20 +468,21 @@ generate_fs(struct llvmpipe_context *lp,
    for (attrib = 0; attrib < shader->info.num_outputs; ++attrib) {
       for(chan = 0; chan < NUM_CHANNELS; ++chan) {
          if(outputs[attrib][chan]) {
-            lp_build_name(outputs[attrib][chan], "output%u.%u.%c", i, attrib, "xyzw"[chan]);
+            LLVMValueRef out = LLVMBuildLoad(builder, outputs[attrib][chan], "");
+            lp_build_name(out, "output%u.%u.%c", i, attrib, "xyzw"[chan]);
 
             switch (shader->info.output_semantic_name[attrib]) {
             case TGSI_SEMANTIC_COLOR:
                {
                   unsigned cbuf = shader->info.output_semantic_index[attrib];
 
-                  lp_build_name(outputs[attrib][chan], "color%u.%u.%c", i, attrib, "rgba"[chan]);
+                  lp_build_name(out, "color%u.%u.%c", i, attrib, "rgba"[chan]);
 
                   /* Alpha test */
                   /* XXX: should the alpha reference value be passed separately? */
 		  /* XXX: should only test the final assignment to alpha */
                   if(cbuf == 0 && chan == 3) {
-                     LLVMValueRef alpha = outputs[attrib][chan];
+                     LLVMValueRef alpha = out;
                      LLVMValueRef alpha_ref_value;
                      alpha_ref_value = lp_jit_context_alpha_ref_value(builder, context_ptr);
                      alpha_ref_value = lp_build_broadcast(builder, vec_type, alpha_ref_value);
@@ -489,13 +490,13 @@ generate_fs(struct llvmpipe_context *lp,
                                          &mask, alpha, alpha_ref_value);
                   }
 
-		  color[cbuf][chan] = outputs[attrib][chan];
+		  color[cbuf][chan] = out;
                   break;
                }
 
             case TGSI_SEMANTIC_POSITION:
                if(chan == 2)
-                  z = outputs[attrib][chan];
+                  z = out;
                break;
             }
          }