diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/glsl/ir_if_return.cpp | 62 |
1 files changed, 61 insertions, 1 deletions
diff --git a/src/glsl/ir_if_return.cpp b/src/glsl/ir_if_return.cpp index 4d59e707869..293f7aa628d 100644 --- a/src/glsl/ir_if_return.cpp +++ b/src/glsl/ir_if_return.cpp @@ -24,13 +24,16 @@ /** * \file ir_if_return.cpp * - * This pass tries to normalize functions to always return from one place. + * This pass tries to normalize functions to always return from one + * place by moving around blocks of code in if statements. * * This helps on hardware with no branching support, and may even be a * useful transform on hardware supporting control flow by turning * masked returns into normal returns. */ +#include <string.h> +#include "glsl_types.h" #include "ir.h" class ir_if_return_visitor : public ir_hierarchical_visitor { @@ -40,6 +43,7 @@ public: this->progress = false; } + ir_visitor_status visit_enter(ir_function_signature *); ir_visitor_status visit_enter(ir_if *); void move_outer_block_inside(ir_instruction *ir, @@ -138,6 +142,62 @@ ir_if_return_visitor::move_outer_block_inside(ir_instruction *ir, } } +/* Normalize a function to always have a return statement at the end. + * + * This avoids the ir_if handler needing to know whether it is at the + * top level of the function to know if there's an implicit return at + * the end of the outer block. + */ +ir_visitor_status +ir_if_return_visitor::visit_enter(ir_function_signature *ir) +{ + ir_return *ret; + + if (!ir->is_defined) + return visit_continue_with_parent; + if (strcmp(ir->function_name(), "main") == 0) + return visit_continue_with_parent; + + ret = find_return_in_block(&ir->body); + + if (ret) { + truncate_after_instruction(ret); + } else { + if (ir->return_type->is_void()) { + ir->body.push_tail(new(ir) ir_return(NULL)); + } else { + /* Probably, if we've got a function with a return value + * hitting this point, it's something like: + * + * float reduce_below_half(float val) + * { + * while () { + * if (val >= 0.5) + * val /= 2.0; + * else + * return val; + * } + * } + * + * So we gain a junk return statement of an undefined value + * at the end that never gets executed. However, a backend + * using this pass is probably desperate to get rid of + * function calls, so go ahead and do it for their sake in + * case it fixes apps. + */ + ir_variable *undef = new(ir) ir_variable(ir->return_type, + "if_return_undef", + ir_var_temporary); + ir->body.push_tail(undef); + + ir_dereference_variable *deref = new(ir) ir_dereference_variable(undef); + ir->body.push_tail(new(ir) ir_return(deref)); + } + } + + return visit_continue; +} + ir_visitor_status ir_if_return_visitor::visit_enter(ir_if *ir) { |