From 4f1f5aa02d24357c160b04ab4a0b72cdb015daff Mon Sep 17 00:00:00 2001
From: Gert Wollny <gert.wollny@collabora.com>
Date: Wed, 3 Sep 2025 16:05:35 +0200
Subject: [PATCH] r600/sfn: Add handling of channels for dest-less ALU ops

This will be used to get rid of some dummy register handling.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37205>
---
 .../drivers/r600/sfn/sfn_instr_alu.cpp        | 40 +++++++++++++++++++
 src/gallium/drivers/r600/sfn/sfn_instr_alu.h  |  5 +++
 2 files changed, 45 insertions(+)

diff --git a/src/gallium/drivers/r600/sfn/sfn_instr_alu.cpp b/src/gallium/drivers/r600/sfn/sfn_instr_alu.cpp
index a8715c0d0b9..55f5f44404c 100644
--- a/src/gallium/drivers/r600/sfn/sfn_instr_alu.cpp
+++ b/src/gallium/drivers/r600/sfn/sfn_instr_alu.cpp
@@ -47,6 +47,34 @@ get_dest_mask(EAluOp opcode, int slots, bool is_cayman_trans)
    UNREACHABLE("dest_mask_from_opcode_and_slots: Some opscodes not handeld");
 }
 
+AluInstr::AluInstr(EAluOp opcode,
+                   int chan,
+                   SrcValues src,
+                   const std::set<AluModifiers>& flags):
+    m_opcode(opcode),
+    m_bank_swizzle(alu_vec_unknown),
+    m_cf_type(cf_alu),
+    m_alu_slots(1),
+    m_fallback_chan(chan)
+{
+   m_src.swap(src);
+
+   if (m_src.size() == 3)
+      m_alu_flags.set(alu_op3);
+
+   for (auto f : flags)
+      m_alu_flags.set(f);
+
+   ASSERT_OR_THROW(m_src.size() ==
+                      static_cast<size_t>(alu_ops.at(opcode).nsrc * m_alu_slots),
+                   "Unexpected number of source values");
+
+   update_uses();
+
+   m_allowed_dest_mask = BITSET_BIT(m_fallback_chan);
+}
+
+
 AluInstr::AluInstr(EAluOp opcode,
                    PRegister dest,
                    SrcValues src,
@@ -1021,6 +1049,18 @@ AluInstr::propagate_death()
    return true;
 }
 
+void AluInstr::set_allowed_dest_chan_mask(uint8_t mask)
+{
+   assert(!m_dest && "We override the fallback channel only");
+   m_allowed_dest_mask = mask;
+
+
+   if (!(BITSET_BIT(m_fallback_chan) & m_allowed_dest_mask)) {
+      unsigned m = mask;
+      m_fallback_chan = u_bit_scan(&m);
+   }
+}
+
 bool
 AluInstr::has_lds_access() const
 {
diff --git a/src/gallium/drivers/r600/sfn/sfn_instr_alu.h b/src/gallium/drivers/r600/sfn/sfn_instr_alu.h
index 13bba1154ef..243a4916fde 100644
--- a/src/gallium/drivers/r600/sfn/sfn_instr_alu.h
+++ b/src/gallium/drivers/r600/sfn/sfn_instr_alu.h
@@ -45,6 +45,10 @@ public:
 
    AluInstr(EAluOp opcode);
    AluInstr(EAluOp opcode, int chan);
+   AluInstr(EAluOp opcode,
+            int chan,
+            SrcValues src,
+            const std::set<AluModifiers>& flags);
    AluInstr(EAluOp opcode,
             PRegister dest,
             SrcValues src0,
@@ -176,6 +180,7 @@ public:
 
    uint8_t allowed_src_chan_mask() const override;
    uint8_t allowed_dest_chan_mask() const {return m_allowed_dest_mask;}
+   void set_allowed_dest_chan_mask(uint8_t mask);
 
    void inc_ar_uses() { ++m_num_ar_uses;}
    auto num_ar_uses() const {return m_num_ar_uses;}