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https://github.com/RPCS3/llvm-mirror.git
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6428f13232
Summary: Lower control flow did not correctly handle the case that a loop break in if/else was on a condition that was not guaranteed to be masked by exec. The first test kernel shows an example of this going wrong; after exiting the loop, exec is all ones, even if it was not before the loop. The fix is for lowering of if-break and else-break to insert an S_AND_B64 to mask the break condition with exec. This commit also includes the optimization of not inserting that S_AND_B64 if it is obviously not needed because the break condition is the result of a V_CMP in the same basic block. V2: Addressed some review comments. V3: Test fixes. Subscribers: arsenm, kzhuravl, wdng, nhaehnle, yaxunl, dstuttard, t-tye, llvm-commits Differential Revision: https://reviews.llvm.org/D44046 Change-Id: I0fc56a01209a9e99d1d5c9b0ffd16f111caf200c llvm-svn: 333258
94 lines
2.9 KiB
LLVM
94 lines
2.9 KiB
LLVM
; RUN: llc -mtriple=amdgcn--amdpal -mcpu=gfx803 -verify-machineinstrs < %s | FileCheck -check-prefix=GCN %s
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; Where the mask of lanes wanting to exit the loop on this iteration is not
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; obviously already masked by exec (in this case, the xor with -1 inserted by
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; control flow annotation), then lower control flow must insert an S_AND_B64
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; with exec.
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; GCN-LABEL: {{^}}needs_and:
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; GCN: s_xor_b64 [[REG1:[^ ,]*]], {{[^ ,]*, -1$}}
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; GCN: s_and_b64 [[REG2:[^ ,]*]], exec, [[REG1]]
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; GCN: s_or_b64 [[REG3:[^ ,]*]], [[REG2]],
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; GCN: s_andn2_b64 exec, exec, [[REG3]]
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define void @needs_and(i32 %arg) {
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entry:
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br label %loop
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loop:
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%tmp23phi = phi i32 [ %tmp23, %endif ], [ 0, %entry ]
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%tmp23 = add nuw i32 %tmp23phi, 1
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%tmp27 = icmp ult i32 %arg, %tmp23
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br i1 %tmp27, label %then, label %endif
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then: ; preds = %bb
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call void @llvm.amdgcn.buffer.store.f32(float undef, <4 x i32> undef, i32 0, i32 undef, i1 false, i1 false) #1
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br label %endif
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endif: ; preds = %bb28, %bb
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br i1 %tmp27, label %loop, label %loopexit
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loopexit:
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ret void
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}
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; Where the mask of lanes wanting to exit the loop on this iteration is
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; obviously already masked by exec (a V_CMP), then lower control flow can omit
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; the S_AND_B64 to avoid an unnecessary instruction.
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; GCN-LABEL: {{^}}doesnt_need_and:
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; GCN: v_cmp{{[^ ]*}} [[REG1:[^ ,]*]]
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; GCN: s_or_b64 [[REG2:[^ ,]*]], [[REG1]],
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; GCN: s_andn2_b64 exec, exec, [[REG2]]
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define void @doesnt_need_and(i32 %arg) {
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entry:
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br label %loop
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loop:
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%tmp23phi = phi i32 [ %tmp23, %loop ], [ 0, %entry ]
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%tmp23 = add nuw i32 %tmp23phi, 1
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%tmp27 = icmp ult i32 %arg, %tmp23
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call void @llvm.amdgcn.buffer.store.f32(float undef, <4 x i32> undef, i32 0, i32 undef, i1 false, i1 false) #1
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br i1 %tmp27, label %loop, label %loopexit
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loopexit:
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ret void
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}
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; Another case where the mask of lanes wanting to exit the loop is not masked
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; by exec, because it is a function parameter.
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; GCN-LABEL: {{^}}break_cond_is_arg:
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; GCN: s_xor_b64 [[REG1:[^ ,]*]], {{[^ ,]*, -1$}}
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; GCN: s_and_b64 [[REG2:[^ ,]*]], exec, [[REG1]]
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; GCN: s_or_b64 [[REG3:[^ ,]*]], [[REG2]],
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; GCN: s_andn2_b64 exec, exec, [[REG3]]
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define void @break_cond_is_arg(i32 %arg, i1 %breakcond) {
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entry:
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br label %loop
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loop:
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%tmp23phi = phi i32 [ %tmp23, %endif ], [ 0, %entry ]
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%tmp23 = add nuw i32 %tmp23phi, 1
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%tmp27 = icmp ult i32 %arg, %tmp23
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br i1 %tmp27, label %then, label %endif
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then: ; preds = %bb
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call void @llvm.amdgcn.buffer.store.f32(float undef, <4 x i32> undef, i32 0, i32 undef, i1 false, i1 false) #1
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br label %endif
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endif: ; preds = %bb28, %bb
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br i1 %breakcond, label %loop, label %loopexit
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loopexit:
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ret void
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}
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declare void @llvm.amdgcn.buffer.store.f32(float, <4 x i32>, i32, i32, i1, i1) #3
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attributes #3 = { nounwind writeonly }
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