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Analyze shared memory alias (#81)

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The purpose of this PR is analyzing shared memory aliases so that we can
fix memory allocation bugs and save memory allocations in triton code
involving complex control flows.

Changes to memory bar and allocation are on the way.

Co-authored-by: Philippe Tillet <phil@openai.com>
This commit is contained in:
Keren Zhou
2022-08-29 10:43:20 -07:00
committed by GitHub
parent 83287d7193
commit 02ebf24d35
15 changed files with 761 additions and 61 deletions
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33
test/Analysis/test-membar.mlir
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@@ -176,3 +176,36 @@ func @multi_blocks_nested_scf(%i1 : i1, %i2 : i1) {
%a_ = triton_gpu.convert_layout %cst0 : (tensor<16x16xf16, #A>) -> tensor<16x16xf16, #AL>
return
}
// CHECK-LABEL: for
func @for(%lb : index, %ub : index, %step : index, %A : !tt.ptr<f16>, %B : !tt.ptr<f16>) {
%a_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16, #A>
%b_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16, #A>
%c_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16, #A>
%a_shared, %b_shared, %c_shared = scf.for %iv = %lb to %ub step %step iter_args(%a_shared = %a_shared_init, %b_shared = %b_shared_init, %c_shared = %c_shared_init) -> (tensor<128x32xf16, #A>, tensor<128x32xf16, #A>, tensor<128x32xf16, #A>) {
// CHECK-NEXT: Membar 3
%cst0 = tt.cat %a_shared, %b_shared {axis = 0} : (tensor<128x32xf16, #A>, tensor<128x32xf16, #A>) -> tensor<256x32xf16, #A>
scf.yield %b_shared, %a_shared, %a_shared : tensor<128x32xf16, #A>, tensor<128x32xf16, #A>, tensor<128x32xf16, #A>
}
return
}
// Although a_shared and b_shared are synced before entering the loop,
// they are reassociated with aliases (c_shared) and thus require a barrier.
// CHECK-LABEL: for_alias
func @for_alias(%lb : index, %ub : index, %step : index, %A : !tt.ptr<f16>, %B : !tt.ptr<f16>) {
%a_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16, #A>
%b_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16, #A>
// CHECK-NEXT: Membar 2
%cst0 = tt.cat %a_shared_init, %b_shared_init {axis = 0} : (tensor<128x32xf16, #A>, tensor<128x32xf16, #A>) -> tensor<256x32xf16, #A>
%c_shared_init = arith.constant dense<0.00e+00> : tensor<128x32xf16, #A>
%a_shared, %b_shared, %c_shared = scf.for %iv = %lb to %ub step %step iter_args(%a_shared = %a_shared_init, %b_shared = %b_shared_init, %c_shared = %c_shared_init) -> (tensor<128x32xf16, #A>, tensor<128x32xf16, #A>, tensor<128x32xf16, #A>) {
%cst1 = tt.cat %a_shared_init, %b_shared_init {axis = 0} : (tensor<128x32xf16, #A>, tensor<128x32xf16, #A>) -> tensor<256x32xf16, #A>
// CHECK-NEXT: Membar 6
%cst2 = tt.cat %a_shared, %b_shared {axis = 0} : (tensor<128x32xf16, #A>, tensor<128x32xf16, #A>) -> tensor<256x32xf16, #A>
scf.yield %c_shared, %a_shared, %b_shared : tensor<128x32xf16, #A>, tensor<128x32xf16, #A>, tensor<128x32xf16, #A>
}
// CHECK-NEXT: Membar 9
%cst3 = tt.cat %cst0, %cst0 {axis = 0} : (tensor<256x32xf16, #A>, tensor<256x32xf16, #A>) -> tensor<512x32xf16, #A>
return
}