[PATCH 3/5] d3dcompiler: Add a dead code elimination pass.

[Zebediah Figura]

Signed-off-by: Zebediah Figura <zfigura at codeweavers.com>
---
 dlls/d3dcompiler_43/hlsl.y | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/dlls/d3dcompiler_43/hlsl.y b/dlls/d3dcompiler_43/hlsl.y
index 15bd0d007b9..932a75bb6dd 100644
--- a/dlls/d3dcompiler_43/hlsl.y
+++ b/dlls/d3dcompiler_43/hlsl.y
@@ -2937,6 +2937,32 @@ static BOOL fold_constants(struct hlsl_ir_node *instr)
     return TRUE;
 }
 
+static BOOL dce(struct hlsl_ir_node *instr)
+{
+    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);
+                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)
@@ -3109,6 +3135,7 @@ HRESULT parse_hlsl(enum shader_type type, DWORD major, DWORD minor,
     list_move_head(entry_func->body, &hlsl_ctx.static_initializers);
 
     while (transform_ir(fold_constants, entry_func->body));
+    while (transform_ir(dce, entry_func->body));
 
     /* Index 0 means unused; index 1 means function entry, so start at 2. */
     index_instructions(entry_func->body, 2);
-- 
2.27.0