From e362310f3d72a45dea7fc6855e5cff3b675b47a1 Mon Sep 17 00:00:00 2001
From: Matthew Poremba <matthew.poremba@amd.com>
Date: Fri, 27 Oct 2023 13:20:56 -0500
Subject: [PATCH] gpu-compute: Update GPR allocation counts

GPR allocation is using fields in the AMD kernel code structure which
are not backwards compatible and are not populated in more recent
compiler versions. Use the granulated fields instead which is enfored to
be backwards compatible.

Change-Id: I718716226f5dbeb08369d5365d5e85b029027932
---
 src/gpu-compute/hsa_queue_entry.hh | 58 ++++++++++++++----------------
 1 file changed, 26 insertions(+), 32 deletions(-)

diff --git a/src/gpu-compute/hsa_queue_entry.hh b/src/gpu-compute/hsa_queue_entry.hh
index 4083c1c85a..84ae139127 100644
--- a/src/gpu-compute/hsa_queue_entry.hh
+++ b/src/gpu-compute/hsa_queue_entry.hh
@@ -70,8 +70,6 @@ class HSAQueueEntry
           _gridSize{{(int)((_hsa_dispatch_packet_t*)disp_pkt)->grid_size_x,
                     (int)((_hsa_dispatch_packet_t*)disp_pkt)->grid_size_y,
                     (int)((_hsa_dispatch_packet_t*)disp_pkt)->grid_size_z}},
-          numVgprs(akc->workitem_vgpr_count),
-          numSgprs(akc->wavefront_sgpr_count),
           _queueId(queue_id), _dispatchId(dispatch_id), dispPkt(disp_pkt),
           _hostDispPktAddr(host_pkt_addr),
           _completionSignal(((_hsa_dispatch_packet_t*)disp_pkt)
@@ -88,40 +86,36 @@ class HSAQueueEntry
           _globalWgId(0), dispatchComplete(false)
 
     {
-        // Precompiled BLIT kernels actually violate the spec a bit
-        // and don't set many of the required akc fields.  For these kernels,
-        // we need to rip register usage from the resource registers.
-        //
-        // We can't get an exact number of registers from the resource
-        // registers because they round, but we can get an upper bound on it.
-        // We determine the number of registers by solving for "vgprs_used"
-        // in the LLVM docs: https://www.llvm.org/docs/AMDGPUUsage.html
+        // Use the resource descriptors to determine number of GPRs. This will
+        // round up in some cases, however the exact number field in the AMD
+        // kernel code struct is not backwards compatible and that field is
+        // not populated in newer compiles. The resource descriptor dword must
+        // be backwards compatible, so use that always.
+        // LLVM docs: https://www.llvm.org/docs/AMDGPUUsage.html
         //     #code-object-v3-kernel-descriptor
+        //
         // Currently, the only supported gfx version in gem5 that computes
-        // this differently is gfx90a.
-        if (!numVgprs) {
-            if (gfx_version == GfxVersion::gfx90a) {
-                numVgprs = (akc->granulated_workitem_vgpr_count + 1) * 8;
-            } else {
-                numVgprs = (akc->granulated_workitem_vgpr_count + 1) * 4;
-            }
+        // VGPR count differently is gfx90a.
+        if (gfx_version == GfxVersion::gfx90a) {
+            numVgprs = (akc->granulated_workitem_vgpr_count + 1) * 8;
+        } else {
+            numVgprs = (akc->granulated_workitem_vgpr_count + 1) * 4;
         }
 
-        if (!numSgprs || numSgprs ==
-            std::numeric_limits<decltype(akc->wavefront_sgpr_count)>::max()) {
-            // Supported major generation numbers: 0 (BLIT kernels), 8, and 9
-            uint16_t version = akc->amd_machine_version_major;
-            assert((version == 0) || (version == 8) || (version == 9));
-            // SGPR allocation granularies:
-            // - GFX8: 8
-            // - GFX9: 16
-            // Source: https://llvm.org/docs/AMDGPUUsage.html
-            if ((version == 0) || (version == 8)) {
-                // We assume that BLIT kernels use the same granularity as GFX8
-                numSgprs = (akc->granulated_wavefront_sgpr_count + 1) * 8;
-            } else if (version == 9) {
-                numSgprs = ((akc->granulated_wavefront_sgpr_count + 1) * 16)/2;
-            }
+        // SGPR allocation granularies:
+        // - GFX8: 8
+        // - GFX9: 16
+        // Source: https://llvm.org/docs/.html
+        if (gfx_version == GfxVersion::gfx801 ||
+                gfx_version == GfxVersion::gfx803) {
+            numSgprs = (akc->granulated_wavefront_sgpr_count + 1) * 8;
+        } else if (gfx_version == GfxVersion::gfx900 ||
+                gfx_version == GfxVersion::gfx902 ||
+                gfx_version == GfxVersion::gfx908 ||
+                gfx_version == GfxVersion::gfx90a) {
+            numSgprs = ((akc->granulated_wavefront_sgpr_count + 1) * 16)/2;
+        } else {
+            panic("Saw unknown gfx version setting up GPR counts\n");
         }
 
         initialVgprState.reset();