PR #6657: [XLA:GPU ] add cuDNN flash attention support in XLA (2nd PR…

… with only MLIR lowering and thunk/runtime)

Imported from GitHub PR openxla/xla#6657

This is the 2nd PR of splitting openxla/xla#5910 with only MLIR lowering and thunk/runtime
1st PR openxla/xla#6293 merged.

* Added MLIR lowering for flash attention.
* Added thunk/runner/runtime support for flash attention.
Copybara import of the project:

--
6f89a7355b4b46cbb974b39ca60e07ae08079f1a by cjkkkk <ske@nvidia.com>:

init mlir lowering and thunk runtime

--
f57b8bee2ba1ad361556c32cb9333c4ac4730016 by cjkkkk <ske@nvidia.com>:

address some comments

Merging this change closes #6657

PiperOrigin-RevId: 580413629

lhlo_gpu/IR/lhlo_gpu_ops.td

@@ -362,7 +362,9 @@ def LHLOGPU_fusedMHAOp : LHLOGPU_Op<"fMHA", [AttrSizedOperandSegments]> {
     FusedMhaDagSignatureAttr:$fused_mha_dag,
     FusedMHAAlgorithmConfigAttr:$algorithm_config,
     OptionalAttr<F64Attr>:$dropout_rate,
-    OptionalAttr<I64Attr>:$seed
+    OptionalAttr<I64Attr>:$seed,
+    BoolAttr:$is_flash_attention,
+    BoolAttr:$is_causal_mask
     );
 }
 
@@ -374,21 +376,30 @@ def LHLOGPU_fusedMHABackwardOp : LHLOGPU_Op<"fMHABackward", [AttrSizedOperandSeg
     Arg<LHLO_Buffer, "", [MemRead]>:$bmm2_grad_gemm1_lhs,
     Arg<LHLO_Buffer, "", [MemRead]>:$d_output,
     Arg<Optional<LHLO_Buffer>, "", [MemRead]>:$mask,
+    Arg<Optional<LHLO_Buffer>, "", [MemRead]>:$bias,
+    Arg<Optional<LHLO_Buffer>, "", [MemRead]>:$fwd_output,
     Arg<LHLO_Buffer, "", [MemWrite]>:$d_bmm1_lhs,
     Arg<LHLO_Buffer, "", [MemWrite]>:$d_bmm1_rhs,
     Arg<LHLO_Buffer, "", [MemWrite]>:$d_bmm2_rhs,
-    Arg<LHLO_Buffer, "", [MemWrite]>:$d_S,
+    Arg<Optional<LHLO_Buffer>, "", [MemWrite]>:$d_S,
+    Arg<Optional<LHLO_Buffer>, "", [MemWrite]>:$softmax_sum,
+    Arg<Optional<LHLO_Buffer>, "", [MemWrite]>:$d_Q_accum,
     Arg<LHLO_Buffer, "", [MemWrite]>:$scratch,
     Arg<Optional<LHLO_Buffer>, "", [MemWrite]>:$d_bias,
     MHLO_DotDimensionNumbers:$bmm1_grad_gemm1_dot_dimension_numbers,
     MHLO_DotDimensionNumbers:$bmm1_grad_gemm2_dot_dimension_numbers,
     MHLO_DotDimensionNumbers:$bmm2_grad_gemm1_dot_dimension_numbers,
     MHLO_DotDimensionNumbers:$bmm2_grad_gemm2_dot_dimension_numbers,
+    I64ArrayAttr:$intermediate_tensor_dimensions,
+    I64ArrayAttr:$intermediate_tensor_layout,
     F64Attr:$fmha_scale,
     FusedMhaBackwardDagSignatureAttr:$fused_mha_dag,
     FusedMHAAlgorithmConfigAttr:$algorithm_config,
     OptionalAttr<F64Attr>:$dropout_rate,
-    OptionalAttr<I64Attr>:$seed);
+    OptionalAttr<I64Attr>:$seed,
+    BoolAttr:$is_flash_attention,
+    BoolAttr:$is_causal_mask
+    );
 }
 
 def LHLOGPU_RadixSortOp: LHLOGPU_Op<"radix_sort", [SameVariadicOperandSize]> {

lhlo_gpu/IR/lhlo_gpu_ops_enums.td

@@ -153,6 +153,8 @@ def FusedMhaBackwardDagScaleBiasSoftmaxDropout : I32EnumAttrCase<"BackwardScaleB
 def FusedMhaBackwardDagScaleBiasSoftmax : I32EnumAttrCase<"BackwardScaleBiasSoftmax", 1>;
 def FusedMhaBackwardDagScaleBiasMaskSoftmax : I32EnumAttrCase<"BackwardScaleBiasMaskSoftmax", 2>;
 def FusedMhaBackwardDagScaleBiasMaskSoftmaxDropout : I32EnumAttrCase<"BackwardScaleBiasMaskSoftmaxDropout", 3>;
+def FusedMhaBackwardDagSoftmax : I32EnumAttrCase<"BackwardSoftmax", 4>;
+def FusedMhaBackwardDagSoftmaxDropout : I32EnumAttrCase<"BackwardSoftmaxDropout", 5>;
 
 def FusedMhaDagSignature: I32EnumAttr<"FusedMhaDagSignature",
     "DAG configuration for Fused Multi-Headed Attention",
@@ -175,11 +177,13 @@ def FusedMhaBackwardDagSignature: I32EnumAttr<"FusedMhaBackwardDagSignature",
     FusedMhaBackwardDagScaleBiasSoftmaxDropout,
     FusedMhaBackwardDagScaleBiasSoftmax,
     FusedMhaBackwardDagScaleBiasMaskSoftmax,
-    FusedMhaBackwardDagScaleBiasMaskSoftmaxDropout]> {
+    FusedMhaBackwardDagScaleBiasMaskSoftmaxDropout,
+    FusedMhaBackwardDagSoftmax,
+    FusedMhaBackwardDagSoftmaxDropout]> {
   let genSpecializedAttr = 0;
   let cppNamespace = "::mlir::lmhlo_gpu";
 }
 
 def FusedMhaDagSignatureAttr : EnumAttr<LmhloGpuDialect, FusedMhaDagSignature, "fused_mha_dag">;
 def FusedMhaBackwardDagSignatureAttr : EnumAttr<LmhloGpuDialect, FusedMhaBackwardDagSignature, "fused_mha_backward_dag">;
-#endif // LHLO_GPU_OPS_ENUMS
+#endif // LHLO_GPU_OPS_ENUMS