glsl2: Don't dead-code eliminate a call where the return value is unused.

This showed up since the disabling of inlining at compile time, which
I apparently didn't regenerate piglit summary for.

Fixes:
glsl-deadcode-call.

src/glsl/ir.h

@@ -1389,4 +1389,7 @@ extern void
 import_prototypes(const exec_list *source, exec_list *dest,
 		  class glsl_symbol_table *symbols, void *mem_ctx);
 
+extern bool
+ir_has_call(ir_instruction *ir);
+
 #endif /* IR_H */

src/glsl/ir_basic_block.cpp

@@ -49,6 +49,14 @@ public:
    bool has_call;
 };
 
+bool
+ir_has_call(ir_instruction *ir)
+{
+   ir_has_call_visitor v;
+   ir->accept(&v);
+   return v.has_call;
+}
+
 /**
  * Calls a user function for every basic block in the instruction stream.
  *
@@ -115,8 +123,6 @@ void call_for_basic_blocks(exec_list *instructions,
 	    call_for_basic_blocks(&ir_sig->body, callback, data);
 	 }
       } else if (ir->as_assignment()) {
-	 ir_has_call_visitor v;
-
 	 /* If there's a call in the expression tree being assigned,
 	  * then that ends the BB too.
 	  *
@@ -130,8 +136,7 @@ void call_for_basic_blocks(exec_list *instructions,
 	  * expression flattener may be useful before using the basic
 	  * block finder to get more maximal basic blocks out.
 	  */
-	 ir->accept(&v);
-	 if (v.has_call) {
+	 if (ir_has_call(ir)) {
 	    callback(leader, ir, data);
 	    leader = NULL;
 	 }

src/glsl/ir_dead_code.cpp

@@ -78,7 +78,8 @@ do_dead_code(exec_list *instructions)
 	  * Don't do so if it's a shader output, though.
 	  */
 	 if (entry->var->mode != ir_var_out &&
-	     entry->var->mode != ir_var_inout) {
+	     entry->var->mode != ir_var_inout &&
+	     !ir_has_call(entry->assign)) {
 	    entry->assign->remove();
 	    progress = true;
 

src/glsl/ir_dead_code_local.cpp

@@ -156,7 +156,12 @@ process_assignment(void *ctx, ir_assignment *ir, exec_list *assignments)
       }
    }
 
-   /* Add this instruction to the assignment list. */
+   /* Add this instruction to the assignment list available to be removed.
+    * But not if the assignment has other side effects.
+    */
+   if (ir_has_call(ir))
+      return progress;
+
    assignment_entry *entry = new(ctx) assignment_entry(var, ir);
    assignments->push_tail(entry);