[BACKEND][LAYOUT] Use LL for AMDMfma related layout conversions (#5210)

Author: Jokeren

lib/Conversion/TritonGPUToLLVM/ConvertLayoutOpToLLVM.cpp

@@ -374,24 +374,24 @@ struct ConvertLayoutOpUsingLinearLayoutsConversion
     // TODO (Keren): Currently, we handle general mma/blocked/slice/dot(ampere)
     // -> mma/blocked/slice/dot(ampere) conversions. The following tasks must be
     // completed before we can remove the layoutIsOK check:
-    // 1. Support for AMD's MFMA and WMMA
+    // 1. Support for AMD's WMMA
     std::function<bool(Attribute)> layoutIsOK = [&](Attribute layout) {
-      if (auto nvidiaMma = dyn_cast<NvidiaMmaEncodingAttr>(layout)) {
-        if (useLegacyMMAConversion) {
-          return false;
-        }
-        return true;
+      if (isa<NvidiaMmaEncodingAttr, AMDMfmaEncodingAttr>(layout)) {
+        return !useLegacyMMAConversion;
       }
       if (auto dotOperand = dyn_cast<DotOperandEncodingAttr>(layout)) {
-        if (auto nvidiaMma =
-                dyn_cast<NvidiaMmaEncodingAttr>(dotOperand.getParent())) {
-          if (useLegacyMMAConversion) {
-            return false;
-          }
+        auto parent = dotOperand.getParent();
+        if (isa<MmaEncodingTrait>(parent) && useLegacyMMAConversion) {
+          return false;
+        }
+        if (auto nvidiaMma = dyn_cast<NvidiaMmaEncodingAttr>(parent)) {
           if (nvidiaMma.isAmpere()) {
             return true;
           }
         }
+        if (isa<AMDMfmaEncodingAttr>(parent)) {
+          return true;
+        }
         return false;
       }
       if (isa<BlockedEncodingAttr>(layout)) {

test/Conversion/amd/mfma-shortcut.mlir

@@ -7,6 +7,7 @@ module attributes {"triton_gpu.num-ctas" = 1 : i32, "triton_gpu.num-warps" = 4 :
   tt.func public @shortcut_mfma16(%arg0: tensor<16x16xf16, #mfma>) {
     // CHECK-NOT: store
     // CHECK-NOT: load
+    // CHECK: llvm.return
     %0 = triton_gpu.convert_layout %arg0 : tensor<16x16xf16, #mfma> -> tensor<16x16xf16, #dotop>
     tt.return
   }
@@ -21,6 +22,7 @@ module attributes {"triton_gpu.num-ctas" = 1 : i32, "triton_gpu.num-warps" = 4 :
   tt.func public @no_shortcut_mfma16(%arg0: tensor<16x16xf16, #mfma>) {
     // CHECK: store
     // CHECK: load
+    // CHECK: llvm.return
     %0 = triton_gpu.convert_layout %arg0 : tensor<16x16xf16, #mfma> -> tensor<16x16xf16, #dotop>
     tt.return
   }