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gallivm: Maximum loop iterations 

Limits maximum loop iterations in a TGSI shader to prevent infinite
loops from occurring, any iteration in any loop counts towards this
limit

Signed-off-by: José Fonseca <jfonseca@vmware.com>
This commit is contained in:
James Benton 2012-04-02 16:29:34 +01:00 committed by José Fonseca
parent d312b224b6
commit 5db9d76a6a
3 changed files with 45 additions and 3 deletions
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5
src/gallium/auxiliary/gallivm/lp_bld_limits.h
View File

@ -51,5 +51,10 @@
*/
#define LP_MAX_TGSI_NESTING 32
/**
* Maximum iterations before loop termination
* Shared between every loop in a TGSI shader
*/
#define LP_MAX_TGSI_LOOP_ITERATIONS 65535
#endif /* LP_BLD_LIMITS_H_ */

1
src/gallium/auxiliary/gallivm/lp_bld_tgsi.h
View File

@ -251,6 +251,7 @@ struct lp_exec_mask {
int call_stack_size;
LLVMValueRef exec_mask;
LLVMValueRef loop_limiter;
};
struct lp_build_tgsi_inst_list

42
src/gallium/auxiliary/gallivm/lp_bld_tgsi_soa.c
View File

@ -66,6 +66,9 @@
static void lp_exec_mask_init(struct lp_exec_mask *mask, struct lp_build_context *bld)
{
LLVMTypeRef int_type = LLVMInt32TypeInContext(bld->gallivm->context);
LLVMBuilderRef builder = bld->gallivm->builder;
mask->bld = bld;
mask->has_mask = FALSE;
mask->cond_stack_size = 0;
@ -75,6 +78,16 @@ static void lp_exec_mask_init(struct lp_exec_mask *mask, struct lp_build_context
mask->int_vec_type = lp_build_int_vec_type(bld->gallivm, mask->bld->type);
mask->exec_mask = mask->ret_mask = mask->break_mask = mask->cont_mask = mask->cond_mask =
LLVMConstAllOnes(mask->int_vec_type);
mask->loop_limiter = LLVMBuildAlloca(
builder,
int_type,
"looplimiter");
LLVMBuildStore(
builder,
LLVMConstInt(int_type, LP_MAX_TGSI_LOOP_ITERATIONS, false),
mask->loop_limiter);
}
static void lp_exec_mask_update(struct lp_exec_mask *mask)
@ -176,6 +189,7 @@ static void lp_exec_bgnloop(struct lp_exec_mask *mask)
LLVMBuildStore(builder, mask->break_mask, mask->break_var);
mask->loop_block = lp_build_insert_new_block(mask->bld->gallivm, "bgnloop");
LLVMBuildBr(builder, mask->loop_block);
LLVMPositionBuilderAtEnd(builder, mask->loop_block);
@ -218,10 +232,11 @@ static void lp_exec_endloop(struct gallivm_state *gallivm,
{
LLVMBuilderRef builder = mask->bld->gallivm->builder;
LLVMBasicBlockRef endloop;
LLVMTypeRef int_type = LLVMInt32TypeInContext(mask->bld->gallivm->context);
LLVMTypeRef reg_type = LLVMIntTypeInContext(gallivm->context,
mask->bld->type.width *
mask->bld->type.length);
LLVMValueRef i1cond;
LLVMValueRef i1cond, i2cond, icond, limiter;
assert(mask->break_mask);
@ -238,17 +253,38 @@ static void lp_exec_endloop(struct gallivm_state *gallivm,
*/
LLVMBuildStore(builder, mask->break_mask, mask->break_var);
/* i1cond = (mask == 0) */
/* Decrement the loop limiter */
limiter = LLVMBuildLoad(builder, mask->loop_limiter, "");
limiter = LLVMBuildSub(
builder,
limiter,
LLVMConstInt(int_type, 1, false),
"");
LLVMBuildStore(builder, limiter, mask->loop_limiter);
/* i1cond = (mask != 0) */
i1cond = LLVMBuildICmp(
builder,
LLVMIntNE,
LLVMBuildBitCast(builder, mask->exec_mask, reg_type, ""),
LLVMConstNull(reg_type), "");
/* i2cond = (looplimiter > 0) */
i2cond = LLVMBuildICmp(
builder,
LLVMIntSGT,
limiter,
LLVMConstNull(int_type), "");
/* if( i1cond && i2cond ) */
icond = LLVMBuildAnd(builder, i1cond, i2cond, "");
endloop = lp_build_insert_new_block(mask->bld->gallivm, "endloop");
LLVMBuildCondBr(builder,
i1cond, mask->loop_block, endloop);
icond, mask->loop_block, endloop);
LLVMPositionBuilderAtEnd(builder, endloop);