glasm: Catch more register leaks

Add support for null registers. These are used when an instruction has
no usages.

This comes handy when an instruction is only used for its CC value, with
the caveat of having to invalidate all pseudo-instructions before
defining the instruction itself in the register allocator. This commits
changes this.

Workaround a bug on Nvidia's condition codes conditional execution using
branches.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/shader_recompiler/backend/glasm/emit_glasm.cpp b/src/shader_recompiler/backend/glasm/emit_glasm.cpp
index 2ce8390592..4aa3682c25 100644
--- a/src/shader_recompiler/backend/glasm/emit_glasm.cpp
+++ b/src/shader_recompiler/backend/glasm/emit_glasm.cpp
@@ -203,7 +203,13 @@ void Precolor(EmitContext& ctx, const IR::Program& program) {
             for (size_t i = 0; i < num_args; ++i) {
                 IR::Block& phi_block{*phi.PhiBlock(i)};
                 auto it{std::find_if_not(phi_block.rbegin(), phi_block.rend(), IsReference).base()};
-                IR::IREmitter{phi_block, it}.PhiMove(phi, phi.Arg(i));
+                IR::IREmitter ir{phi_block, it};
+                const IR::Value arg{phi.Arg(i)};
+                if (arg.IsImmediate()) {
+                    ir.PhiMove(phi, arg);
+                } else {
+                    ir.PhiMove(phi, IR::Value{&RegAlloc::AliasInst(*arg.Inst())});
+                }
             }
             for (size_t i = 0; i < num_args; ++i) {
                 IR::IREmitter{*phi.PhiBlock(i)}.Reference(IR::Value{&phi});