Mesa (main): aco/ra: only use VCC if program->needs_vcc == true

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Module: Mesa
Branch: main
Commit: 44fb9ba84ac1048bd045b147546a2731962ea458
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=44fb9ba84ac1048bd045b147546a2731962ea458

Author: Daniel Schürmann <daniel at schuermann.dev>
Date:   Wed Mar 16 10:59:52 2022 +0100

aco/ra: only use VCC if program->needs_vcc == true

A future commit will make VCC register assignment independent
from register hints. Up to GFX9, VCC can alternatively be used
as regular SGPR, so prevent overlap.

Reviewed-by: Rhys Perry <pendingchaos02 at gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15408>

---

 src/amd/compiler/aco_live_var_analysis.cpp   | 2 +-
 src/amd/compiler/aco_register_allocation.cpp | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/amd/compiler/aco_live_var_analysis.cpp b/src/amd/compiler/aco_live_var_analysis.cpp
index 48456fc0df8..abe839642af 100644
--- a/src/amd/compiler/aco_live_var_analysis.cpp
+++ b/src/amd/compiler/aco_live_var_analysis.cpp
@@ -421,7 +421,7 @@ live_var_analysis(Program* program)
    std::vector<PhiInfo> phi_info(program->blocks.size());
    RegisterDemand new_demand;
 
-   program->needs_vcc = false;
+   program->needs_vcc = program->chip_class >= GFX10;
 
    /* this implementation assumes that the block idx corresponds to the block's position in
     * program->blocks vector */
diff --git a/src/amd/compiler/aco_register_allocation.cpp b/src/amd/compiler/aco_register_allocation.cpp
index 41c36603608..0204f934bb3 100644
--- a/src/amd/compiler/aco_register_allocation.cpp
+++ b/src/amd/compiler/aco_register_allocation.cpp
@@ -1398,7 +1398,7 @@ get_reg_specified(ra_ctx& ctx, RegisterFile& reg_file, RegClass rc, aco_ptr<Inst
    PhysRegInterval bounds = get_reg_bounds(ctx.program, rc.type());
    PhysRegInterval vcc_win = {vcc, 2};
    /* VCC is outside the bounds */
-   bool is_vcc = rc.type() == RegType::sgpr && vcc_win.contains(reg_win);
+   bool is_vcc = rc.type() == RegType::sgpr && vcc_win.contains(reg_win) && ctx.program->needs_vcc;
    bool is_m0 = rc == s1 && reg == m0;
    if (!bounds.contains(reg_win) && !is_vcc && !is_m0)
       return false;