From ad5fbc440767ee020ebf761bd7f3aaba0895c92d Mon Sep 17 00:00:00 2001
From: Georg Lehmann <dadschoorse@gmail.com>
Date: Thu, 8 Feb 2024 14:51:25 +0100
Subject: [PATCH] aco: use fmamk/ak instead of fma with inline constant for
 more VOPD
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Foz-DB navi31, forced wave32:
Totals from 24438 (31.29% of 78112) affected shaders:
Instrs: 21632788 -> 21551766 (-0.37%); split: -0.38%, +0.01%
CodeSize: 126181860 -> 126083848 (-0.08%); split: -0.10%, +0.02%
Latency: 162491062 -> 162516234 (+0.02%); split: -0.05%, +0.07%
InvThroughput: 31121194 -> 31002125 (-0.38%); split: -0.40%, +0.02%
VClause: 420176 -> 420169 (-0.00%); split: -0.00%, +0.00%
SClause: 791844 -> 791762 (-0.01%); split: -0.01%, +0.00%

Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27523>
---
 src/amd/compiler/aco_optimizer_postRA.cpp | 35 +++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/src/amd/compiler/aco_optimizer_postRA.cpp b/src/amd/compiler/aco_optimizer_postRA.cpp
index cee1fd0cb57..25be6300ee3 100644
--- a/src/amd/compiler/aco_optimizer_postRA.cpp
+++ b/src/amd/compiler/aco_optimizer_postRA.cpp
@@ -708,6 +708,39 @@ try_reassign_split_vector(pr_opt_ctx& ctx, aco_ptr<Instruction>& instr)
    }
 }
 
+void
+try_convert_fma_to_vop2(pr_opt_ctx& ctx, aco_ptr<Instruction>& instr)
+{
+   /* We convert v_fma_f32 with inline constant to fmamk/fmaak.
+    * This is only benefical if it allows more VOPD.
+    */
+   if (ctx.program->gfx_level < GFX11 || ctx.program->wave_size != 32 ||
+       instr->opcode != aco_opcode::v_fma_f32 || instr->usesModifiers())
+      return;
+
+   int constant_idx = -1;
+   int vgpr_idx = -1;
+   for (int i = 0; i < 3; i++) {
+      const Operand& op = instr->operands[i];
+      if (op.isConstant() && !op.isLiteral())
+         constant_idx = i;
+      else if (op.isOfType(RegType::vgpr))
+         vgpr_idx = i;
+      else
+         return;
+   }
+
+   if (constant_idx < 0 || vgpr_idx < 0)
+      return;
+
+   std::swap(instr->operands[constant_idx], instr->operands[2]);
+   if (constant_idx == 0 || vgpr_idx == 0)
+      std::swap(instr->operands[0], instr->operands[1]);
+   instr->operands[2] = Operand::literal32(instr->operands[2].constantValue());
+   instr->opcode = constant_idx == 2 ? aco_opcode::v_fmaak_f32 : aco_opcode::v_fmamk_f32;
+   instr->format = Format::VOP2;
+}
+
 void
 process_instruction(pr_opt_ctx& ctx, aco_ptr<Instruction>& instr)
 {
@@ -726,6 +759,8 @@ process_instruction(pr_opt_ctx& ctx, aco_ptr<Instruction>& instr)
 
    try_reassign_split_vector(ctx, instr);
 
+   try_convert_fma_to_vop2(ctx, instr);
+
    if (instr)
       save_reg_writes(ctx, instr);