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Summary: This extends the PeelingModuloScheduleExpander to generate prolog and epilog code, and correctly stitch uses through the prolog, kernel, epilog DAG. The key concept in this patch is to ensure that all transforms are *local*; only a function of a block and its immediate predecessor and successor. By defining the problem in this way we can inductively rewrite the entire DAG using only local knowledge that is easy to reason about. For example, we assume that all prologs and epilogs are near-perfect clones of the steady-state kernel. This means that if a block has an instruction that is predicated out, we can redirect all users of that instruction to that equivalent instruction in our immediate predecessor. As all blocks are clones, every instruction must have an equivalent in every other block. Similarly we can make the assumption by construction that if a value defined in a block is used outside that block, the only possible user is its immediate successors. We maintain this even for values that are used outside the loop by creating a limited form of LCSSA. This code isn't small, but it isn't complex. Enabled a bunch of testing from Hexagon. There are a couple of tests not enabled yet; I'm about 80% sure there isn't buggy codegen but the tests are checking for patterns that we don't produce. Those still need a bit more investigation. In the meantime we (Google) are happy with the code produced by this on our downstream SMS implementation, and believe it generates correct code. Subscribers: mgorny, hiraditya, jsji, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D68205 llvm-svn: 373462
71 lines
2.2 KiB
LLVM
71 lines
2.2 KiB
LLVM
; RUN: llc -march=hexagon -enable-pipeliner -enable-pipeliner-opt-size \
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; RUN: -verify-machineinstrs -hexagon-initial-cfg-cleanup=0 \
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; RUN: -enable-aa-sched-mi=false -hexagon-expand-condsets=0 \
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; RUN: < %s -pipeliner-experimental-cg=true | FileCheck %s
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; Disable expand-condsets because it will assert on undefined registers.
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; Test that we change the CFG correctly for pipelined loops where the trip
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; count is a compile-time constant, and the trip count is the same as the
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; number of prolog blocks (i.e., stages).
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; CHECK: memb(r{{[0-9]+}}+#0) =
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; CHECK: memb(r{{[0-9]+}}+#0) =
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; Function Attrs: nounwind optsize
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define void @f0(i1 %x) #0 {
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b0:
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br label %b1
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b1: ; preds = %b5, %b0
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%v0 = load i16, i16* undef, align 2, !tbaa !0
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%v1 = sext i16 %v0 to i32
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%v2 = load i16, i16* undef, align 2, !tbaa !0
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%v3 = sext i16 %v2 to i32
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%v4 = and i32 %v1, 7
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%v5 = and i32 %v3, 7
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br label %b2
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b2: ; preds = %b4, %b1
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br label %b3
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b3: ; preds = %b3, %b2
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%v6 = phi i32 [ 0, %b2 ], [ %v22, %b3 ]
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%v7 = add i32 %v6, undef
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%v8 = icmp slt i32 undef, %v7
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%v9 = add nsw i32 %v7, 1
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%v10 = select i1 %x, i32 1, i32 %v9
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%v11 = add i32 %v10, 0
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%v12 = getelementptr inbounds i8, i8* null, i32 %v11
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%v13 = load i8, i8* %v12, align 1, !tbaa !4
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%v14 = zext i8 %v13 to i32
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%v15 = mul i32 %v14, %v4
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%v16 = add i32 %v15, 0
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%v17 = mul i32 %v16, %v5
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%v18 = add i32 %v17, 32
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%v19 = add i32 %v18, 0
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%v20 = lshr i32 %v19, 6
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%v21 = trunc i32 %v20 to i8
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store i8 %v21, i8* undef, align 1, !tbaa !4
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%v22 = add i32 %v6, 1
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%v23 = icmp eq i32 %v22, 2
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br i1 %v23, label %b4, label %b3
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b4: ; preds = %b3
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br i1 undef, label %b5, label %b2
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b5: ; preds = %b4
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br i1 undef, label %b1, label %b6
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b6: ; preds = %b5
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ret void
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}
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attributes #0 = { nounwind optsize "target-cpu"="hexagonv55" }
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!0 = !{!1, !1, i64 0}
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!1 = !{!"short", !2}
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!2 = !{!"omnipotent char", !3}
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!3 = !{!"Simple C/C++ TBAA"}
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!4 = !{!2, !2, i64 0}
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