From 8e5ec33f1151dd82402bdfdaa4fff7c284e49a1c Mon Sep 17 00:00:00 2001 From: Eric Anholt Date: Wed, 30 Nov 2016 17:27:37 -0800 Subject: [PATCH] vc4: In a loop break/continue, jump if everyone has taken the path. This should be a win for most loops, which tend to have uniform control flow. More importantly, it exposes important information to live variables: that the break/continue here means that our jump target may have access to values that were live on our input. Previously, we were just setting the exec mask and letting control flow fall through, so an intervening def between the break and the end of the loop would appear to live variables as if it screened off the variable, when it didn't actually. Fixes a regression in glsl-vs-loop-redundant-condition.shader_test when a perturbing of register allocation caused a live variable to get stomped. Cc: 13.0 --- src/gallium/drivers/vc4/vc4_program.c | 27 +++++++++++++++++---------- 1 file changed, 17 insertions(+), 10 deletions(-) diff --git a/src/gallium/drivers/vc4/vc4_program.c b/src/gallium/drivers/vc4/vc4_program.c index 66fd902b695..a7c92d577b8 100644 --- a/src/gallium/drivers/vc4/vc4_program.c +++ b/src/gallium/drivers/vc4/vc4_program.c @@ -1957,22 +1957,29 @@ ntq_emit_if(struct vc4_compile *c, nir_if *if_stmt) static void ntq_emit_jump(struct vc4_compile *c, nir_jump_instr *jump) { + struct qblock *jump_block; switch (jump->type) { case nir_jump_break: - qir_SF(c, c->execute); - qir_MOV_cond(c, QPU_COND_ZS, c->execute, - qir_uniform_ui(c, c->loop_break_block->index)); + jump_block = c->loop_break_block; break; - case nir_jump_continue: - qir_SF(c, c->execute); - qir_MOV_cond(c, QPU_COND_ZS, c->execute, - qir_uniform_ui(c, c->loop_cont_block->index)); + jump_block = c->loop_cont_block; break; - - case nir_jump_return: - unreachable("All returns shouold be lowered\n"); + default: + unreachable("Unsupported jump type\n"); } + + qir_SF(c, c->execute); + qir_MOV_cond(c, QPU_COND_ZS, c->execute, + qir_uniform_ui(c, jump_block->index)); + + /* Jump to the destination block if everyone has taken the jump. */ + qir_SF(c, qir_SUB(c, c->execute, qir_uniform_ui(c, jump_block->index))); + qir_BRANCH(c, QPU_COND_BRANCH_ALL_ZS); + struct qblock *new_block = qir_new_block(c); + qir_link_blocks(c->cur_block, jump_block); + qir_link_blocks(c->cur_block, new_block); + qir_set_emit_block(c, new_block); } static void -- 2.30.2