From 46047cf5ca59ea612f7be54f6c206cc9948aba3b Mon Sep 17 00:00:00 2001
From: Rhys Perry <pendingchaos02@gmail.com>
Date: Thu, 9 Apr 2026 13:56:16 +0100
Subject: [PATCH] aco/ra: fix fill() with certain subdword cases
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If div_ceil(start.byte() + num_bytes, 4) != div_ceil(num_bytes, 4), like
v3b at byte=2.

Also, the non-const operator[] was unused and unsafe.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/41018>
---
 src/amd/compiler/aco_register_allocation.cpp | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/amd/compiler/aco_register_allocation.cpp b/src/amd/compiler/aco_register_allocation.cpp
index e99b53fd560..7cf7e0c5c4d 100644
--- a/src/amd/compiler/aco_register_allocation.cpp
+++ b/src/amd/compiler/aco_register_allocation.cpp
@@ -329,8 +329,6 @@ public:
 
    const uint32_t& operator[](PhysReg index) const { return regs[index]; }
 
-   uint32_t& operator[](PhysReg index) { return regs[index]; }
-
    unsigned count_zero(PhysRegInterval reg_interval) const
    {
       unsigned res = 0;
@@ -457,8 +455,9 @@ private:
 
    void fill_subdword(PhysReg start, unsigned num_bytes, uint32_t val)
    {
-      fill(start, DIV_ROUND_UP(num_bytes, 4), 0xF0000000);
       for (PhysReg i = start; i.reg_b < start.reg_b + num_bytes; i = PhysReg(i + 1)) {
+         regs[i] = 0xF0000000;
+
          /* emplace or get */
          std::array<uint32_t, 4>& sub =
             subdword_regs.emplace(i, std::array<uint32_t, 4>{0, 0, 0, 0}).first->second;