From b28eb9d4a0b28f4a28afa08a64063be492532041 Mon Sep 17 00:00:00 2001 From: Connor Abbott Date: Tue, 2 Sep 2014 20:14:56 -0400 Subject: [PATCH] r300g: set register classes before interferences In commit 567e2769b81863b6dffdac3826a6b729ce6ea37c ("ra: make the p, q test more efficient") I unknowingly introduced a new requirement to the register allocator API: the user must set the register class of all nodes before setting up their interferences, because ra_add_conflict_list() now uses the classes of the two interfering nodes. i965 already did this, but r300g was setting up register classes interleaved with setting up the interference graph. This led to us calculating the wrong q total, and in certain cases e78a01d5e6f77e075fe667a0f0ccb10d89c0dd58 (" ra: optimistically color only one node at a time") made it so that this bug caused a segfault. In particular, the error occurred if the q total was decremented to 1 below 0 for the last node to be pushed onto the stack. Since q_total is an unsigned integer, it overflowed to 0xffffffff, which is what lowest_q_total happens to be initialzed to. This means that we would fail the "new_q_total < lowest_q_total" check on line 476 of register_allocate.c, and so the node would never be pushed onto the stack, which led to segfaults in ra_select() when we failed to ever give it a register. Signed-off-by: Connor Abbott --- I think we could get rid of the node_classes array if we call ra_alloc_interference_graph() earlier, but I don't know much about this code so I just did the minimum amount to fix it. src/gallium/drivers/r300/compiler/radeon_pair_regalloc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/src/gallium/drivers/r300/compiler/radeon_pair_regalloc.c b/src/gallium/drivers/r300/compiler/radeon_pair_regalloc.c index 936c88d..b854a2f 100644 --- a/src/gallium/drivers/r300/compiler/radeon_pair_regalloc.c +++ b/src/gallium/drivers/r300/compiler/radeon_pair_regalloc.c @@ -572,14 +572,16 @@ static void do_advanced_regalloc(struct regalloc_state * s) graph = ra_alloc_interference_graph(ra_state->regs, node_count + s->NumInputs); + for (node_index = 0; node_index < node_count; node_index++) { + ra_set_node_class(graph, node_index, node_classes[node_index]); + } + /* Build the interference graph */ for (var_ptr = variables, node_index = 0; var_ptr; var_ptr = var_ptr->Next,node_index++) { struct rc_list * a, * b; unsigned int b_index; - ra_set_node_class(graph, node_index, node_classes[node_index]); - for (a = var_ptr, b = var_ptr->Next, b_index = node_index + 1; b; b = b->Next, b_index++) { struct rc_variable * var_a = a->Item; -- 1.8.5.2 (Apple Git-48)