Commit ee1c69fa authored by Ian Romanick's avatar Ian Romanick

glsl: Don't increase the iteration count when there are no terminators

Incrementing the iteration count was intended to fix an off-by-one error
when the first terminator was superseded by a later terminator.  If
there is no first terminator or later terminator, there is no off-by-one
error.  Incrementing the loop count creates one.  This can be seen in
loops like:

    do {
        if (something) {
            // No breaks or continues here.
    } while (false);
Reviewed-by: Timothy Arceri's avatarTimothy Arceri <>
Tested-by: Abel Briggs's avatarAbel Briggs <>
Fixes: 646621c6 ("glsl: make loop unrolling more like the nir unrolling path")
parent 5c4289dd
......@@ -180,6 +180,11 @@ loop_unroll_visitor::simple_unroll(ir_loop *ir, int iterations)
void *const mem_ctx = ralloc_parent(ir);
loop_variable_state *const ls = this->state->get(ir);
/* If there are no terminators, then the loop iteration count must be 1.
* This is the 'do { } while (false);' case.
assert(!ls->terminators.is_empty() || iterations == 1);
ir_instruction *first_ir =
(ir_instruction *) ir->body_instructions.get_head();
......@@ -221,7 +226,8 @@ loop_unroll_visitor::simple_unroll(ir_loop *ir, int iterations)
* the loop, or it the exit branch contains instructions. This ensures we
* execute any instructions before the terminator or in its exit branch.
if (limit_if != first_ir->as_if() || exit_branch_has_instructions)
if (!ls->terminators.is_empty() &&
(limit_if != first_ir->as_if() || exit_branch_has_instructions))
for (int i = 0; i < iterations; i++) {
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