fdo-mirrors/mesa
1
0
Fork 0
mirror of https://gitlab.freedesktop.org/mesa/mesa.git synced 2026-01-19 06:40:32 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions 1

Check for constant-valued while/do loop conditions.

Browse source 
Allows us to:
1. avoid generating constant-valued BRK test for while(1)..
2. discard entire loop for while(0).
3. detection infinite loops at compile-time.
This commit is contained in:
Brian 2007-02-08 17:40:29 -07:00
parent c0a9f554be
commit bd9615bbc5
1 changed files with 58 additions and 8 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

66
src/mesa/shader/slang/slang_codegen.c
View file

@ -1408,19 +1408,48 @@ _slang_gen_function_call_name(slang_assemble_ctx *A, const char *name,
}
static GLboolean
_slang_is_constant_cond(const slang_operation *oper, GLboolean *value)
{
if (oper->type == slang_oper_literal_float ||
oper->type == slang_oper_literal_int ||
oper->type == slang_oper_literal_bool) {
if (oper->literal[0])
*value = GL_TRUE;
else
*value = GL_FALSE;
return GL_TRUE;
}
else if (oper->type == slang_oper_expression &&
oper->num_children == 1) {
return _slang_is_constant_cond(&oper->children[0], value);
}
return GL_FALSE;
}
/**
* Generate loop code using high-level IR_LOOP instruction
*/
static slang_ir_node *
_slang_gen_while(slang_assemble_ctx * A, const slang_operation *oper)
{
slang_ir_node *prevLoop;
/*
* LOOP:
* BREAK if !expr (child[0])
* body code (child[1])
*/
slang_ir_node *loop, *cond, *breakIf, *body;
slang_ir_node *prevLoop, *loop, *cond, *breakIf, *body;
GLboolean isConst, constTrue;
/* Check if loop condition is a constant */
isConst = _slang_is_constant_cond(&oper->children[0], &constTrue);
if (isConst && !constTrue) {
/* loop is never executed! */
return new_node0(IR_NOP);
}
loop = new_loop(NULL);
@ -1429,10 +1458,23 @@ _slang_gen_while(slang_assemble_ctx * A, const slang_operation *oper)
A->CurLoop = loop;
cond = new_cond(_slang_gen_operation(A, &oper->children[0]));
breakIf = new_break_if(A->CurLoop, cond, GL_FALSE);
if (isConst && constTrue) {
/* while(nonzero constant), no conditional break */
breakIf = NULL;
}
else {
breakIf = new_break_if(A->CurLoop, cond, GL_FALSE);
}
body = _slang_gen_operation(A, &oper->children[1]);
loop->Children[0] = new_seq(breakIf, body);
/* Do infinite loop detection */
if (loop->BranchNode == 0 && isConst && constTrue) {
/* infinite loop detected */
A->CurLoop = prevLoop; /* clean-up */
RETURN_ERROR("Infinite loop detected!", 0);
}
/* pop loop, restore prev */
A->CurLoop = prevLoop;
@ -1446,13 +1488,16 @@ _slang_gen_while(slang_assemble_ctx * A, const slang_operation *oper)
static slang_ir_node *
_slang_gen_do(slang_assemble_ctx * A, const slang_operation *oper)
{
slang_ir_node *prevLoop;
/*
* LOOP:
* body code (child[0])
* BREAK if !expr (child[1])
*/
slang_ir_node *loop, *cond, *breakIf, *body;
slang_ir_node *prevLoop, *loop, *cond, *breakIf, *body;
GLboolean isConst, constTrue;
/* Check if loop condition is a constant */
isConst = _slang_is_constant_cond(&oper->children[0], &constTrue);
loop = new_loop(NULL);
@ -1462,7 +1507,13 @@ _slang_gen_do(slang_assemble_ctx * A, const slang_operation *oper)
body = _slang_gen_operation(A, &oper->children[0]);
cond = new_cond(_slang_gen_operation(A, &oper->children[1]));
breakIf = new_break_if(A->CurLoop, cond, GL_FALSE);
if (isConst && constTrue) {
/* while(nonzero constant), no conditional break */
breakIf = NULL;
}
else {
breakIf = new_break_if(A->CurLoop, cond, GL_FALSE);
}
loop->Children[0] = new_seq(body, breakIf);
/* pop loop, restore prev */
@ -1478,7 +1529,6 @@ _slang_gen_do(slang_assemble_ctx * A, const slang_operation *oper)
static slang_ir_node *
_slang_gen_for(slang_assemble_ctx * A, const slang_operation *oper)
{
slang_ir_node *prevLoop;
/*
* init (child[0])
* LOOP:
@ -1486,7 +1536,7 @@ _slang_gen_for(slang_assemble_ctx * A, const slang_operation *oper)
* body code (child[3])
* incr code (child[2]) // XXX continue here
*/
slang_ir_node *loop, *cond, *breakIf, *body, *init, *incr;
slang_ir_node *prevLoop, *loop, *cond, *breakIf, *body, *init, *incr;
init = _slang_gen_operation(A, &oper->children[0]);
loop = new_loop(NULL);