Zebediah Figura : vkd3d-shader: Add a dead code elimination pass.

[Alexandre Julliard]

Module: vkd3d
Branch: master
Commit: 7c2083d37414ba0200d0ecca736b16fdd8c0491d
URL:    https://source.winehq.org/git/vkd3d.git/?a=commit;h=7c2083d37414ba0200d0ecca...

Author: Zebediah Figura 
Date:   Tue Mar 16 16:31:54 2021 -0500

vkd3d-shader: Add a dead code elimination pass.

Signed-off-by: Zebediah Figura 
Signed-off-by: Matteo Bruni 
Signed-off-by: Henri Verbeet 
Signed-off-by: Alexandre Julliard

---

libs/vkd3d-shader/hlsl_codegen.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/libs/vkd3d-shader/hlsl_codegen.c b/libs/vkd3d-shader/hlsl_codegen.c
index c8d8d17..22ad3ed 100644
--- a/libs/vkd3d-shader/hlsl_codegen.c
+++ b/libs/vkd3d-shader/hlsl_codegen.c
@@ -120,6 +120,32 @@ static bool fold_constants(struct hlsl_ctx *ctx, struct hlsl_ir_node *instr, voi
     return true;
 }

+static bool dce(struct hlsl_ctx *ctx, struct hlsl_ir_node *instr, void *context)
+{
+    switch (instr->type)
+    {
+        case HLSL_IR_CONSTANT:
+        case HLSL_IR_EXPR:
+        case HLSL_IR_LOAD:
+        case HLSL_IR_SWIZZLE:
+            if (list_empty(&instr->uses))
+            {
+                list_remove(&instr->entry);
+                hlsl_free_instr(instr);
+                return true;
+            }
+            break;
+
+        case HLSL_IR_ASSIGNMENT:
+        case HLSL_IR_IF:
+        case HLSL_IR_JUMP:
+        case HLSL_IR_LOOP:
+            break;
+    }
+
+    return false;
+}
+
 /* Allocate a unique, ordered index to each instruction, which will be used for
  * computing liveness ranges. */
 static unsigned int index_instructions(struct list *instrs, unsigned int index)
@@ -264,6 +290,7 @@ int hlsl_emit_dxbc(struct hlsl_ctx *ctx, struct hlsl_ir_function_decl *entry_fun
     list_move_head(entry_func->body, &ctx->static_initializers);

while (transform_ir(ctx, fold_constants, entry_func->body, NULL));
+    while (transform_ir(ctx, dce, entry_func->body, NULL));

/* Index 0 means unused; index 1 means function entry, so start at 2. */
     index_instructions(entry_func->body, 2);