b604fcb7bc
The runtime unroller will try to produce a non-loop if the unroll count is 2 and thus the prolog/epilog loop would only run at most one iteration. The old implementation did this by avoiding loop construction entirely. This patches instead constructs the trivial loop and then explicitly breaks the backedge and simplifies. This does result in some additional code churn when triggered, but a) results in better quality code and b) removes a codepath which didn't work properly for multiple exit epilogs. One oddity that I want to draw to reviewer attention is that this somehow changes revisit order. The new order looks equivalent to me, but I don't understand how creating and erasing an extra loop here creates this effect. Differential Revision: https://reviews.llvm.org/D108521
157 lines
5.2 KiB
LLVM
157 lines
5.2 KiB
LLVM
; This test checks that nested loops are revisited in various scenarios when
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; unrolling. Note that if we ever start doing outer loop peeling a test case
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; for that should be added here that will look essentially like a hybrid of the
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; current two cases.
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;
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; RUN: opt < %s -disable-output -debug-pass-manager 2>&1 \
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; RUN: -passes='require<opt-remark-emit>,loop(loop-unroll-full)' \
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; RUN: | FileCheck %s
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;
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; Also run in a special mode that visits children.
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; RUN: opt < %s -disable-output -debug-pass-manager -unroll-revisit-child-loops 2>&1 \
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; RUN: -passes='require<opt-remark-emit>,loop(loop-unroll-full)' \
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; RUN: | FileCheck %s --check-prefixes=CHECK,CHECK-CHILDREN
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; Basic test is fully unrolled and we revisit the post-unroll new sibling
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; loops, including the ones that used to be child loops.
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define void @full_unroll(i1* %ptr) {
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; CHECK-LABEL: OptimizationRemarkEmitterAnalysis on full_unroll
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; CHECK-NOT: LoopFullUnrollPass
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entry:
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br label %l0
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l0:
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%cond.0 = load volatile i1, i1* %ptr
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br i1 %cond.0, label %l0.0.ph, label %exit
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l0.0.ph:
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br label %l0.0
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l0.0:
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%iv = phi i32 [ %iv.next, %l0.0.latch ], [ 0, %l0.0.ph ]
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%iv.next = add i32 %iv, 1
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br label %l0.0.0.ph
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l0.0.0.ph:
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br label %l0.0.0
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l0.0.0:
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%cond.0.0.0 = load volatile i1, i1* %ptr
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br i1 %cond.0.0.0, label %l0.0.0, label %l0.0.1.ph
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; CHECK: LoopFullUnrollPass on Loop at depth 3 containing: %l0.0.0<header>
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; CHECK-NOT: LoopFullUnrollPass
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l0.0.1.ph:
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br label %l0.0.1
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l0.0.1:
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%cond.0.0.1 = load volatile i1, i1* %ptr
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br i1 %cond.0.0.1, label %l0.0.1, label %l0.0.latch
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; CHECK: LoopFullUnrollPass on Loop at depth 3 containing: %l0.0.1<header>
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; CHECK-NOT: LoopFullUnrollPass
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l0.0.latch:
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%cmp = icmp slt i32 %iv.next, 2
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br i1 %cmp, label %l0.0, label %l0.latch
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; CHECK: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0
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; CHECK-NOT: LoopFullUnrollPass
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;
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; Unrolling occurs, so we visit what were the inner loops twice over. First we
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; visit their clones, and then we visit the original loops re-parented.
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; CHECK: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0.1.1<header>
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; CHECK-NOT: LoopFullUnrollPass
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; CHECK: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0.0.1<header>
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; CHECK-NOT: LoopFullUnrollPass
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; CHECK: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0.1<header>
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; CHECK-NOT: LoopFullUnrollPass
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; CHECK: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0.0<header>
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; CHECK-NOT: LoopFullUnrollPass
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l0.latch:
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br label %l0
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; CHECK: LoopFullUnrollPass on Loop at depth 1 containing: %l0<header>
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; CHECK-NOT: LoopFullUnrollPass
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exit:
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ret void
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}
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; Now we test forced runtime partial unrolling with metadata. Here we end up
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; duplicating child loops without changing their structure and so they aren't by
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; default visited, but will be visited with a special parameter.
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define void @partial_unroll(i32 %count, i1* %ptr) {
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; CHECK-LABEL: OptimizationRemarkEmitterAnalysis on partial_unroll
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; CHECK-NOT: LoopFullUnrollPass
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entry:
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br label %l0
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l0:
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%cond.0 = load volatile i1, i1* %ptr
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br i1 %cond.0, label %l0.0.ph, label %exit
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l0.0.ph:
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br label %l0.0
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l0.0:
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%iv = phi i32 [ %iv.next, %l0.0.latch ], [ 0, %l0.0.ph ]
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%iv.next = add i32 %iv, 1
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br label %l0.0.0.ph
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l0.0.0.ph:
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br label %l0.0.0
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l0.0.0:
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%cond.0.0.0 = load volatile i1, i1* %ptr
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br i1 %cond.0.0.0, label %l0.0.0, label %l0.0.1.ph
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; CHECK: LoopFullUnrollPass on Loop at depth 3 containing: %l0.0.0<header>
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; CHECK-NOT: LoopFullUnrollPass
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l0.0.1.ph:
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br label %l0.0.1
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l0.0.1:
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%cond.0.0.1 = load volatile i1, i1* %ptr
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br i1 %cond.0.0.1, label %l0.0.1, label %l0.0.latch
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; CHECK: LoopFullUnrollPass on Loop at depth 3 containing: %l0.0.1<header>
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; CHECK-NOT: LoopFullUnrollPass
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l0.0.latch:
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%cmp = icmp slt i32 %iv.next, %count
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br i1 %cmp, label %l0.0, label %l0.latch, !llvm.loop !1
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; CHECK: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0
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; CHECK-NOT: LoopFullUnrollPass
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;
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; Partial unrolling occurs which introduces both new child loops and new sibling
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; loops. We only visit the child loops in a special mode, not by default.
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; CHECK-CHILDREN: LoopFullUnrollPass on Loop at depth 3 containing: %l0.0.0<header>
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; CHECK-CHILDREN-NOT: LoopFullUnrollPass
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; CHECK-CHILDREN: LoopFullUnrollPass on Loop at depth 3 containing: %l0.0.1<header>
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; CHECK-CHILDREN-NOT: LoopFullUnrollPass
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; CHECK-CHILDREN: LoopFullUnrollPass on Loop at depth 3 containing: %l0.0.0.1<header>
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; CHECK-CHILDREN-NOT: LoopFullUnrollPass
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; CHECK-CHILDREN: LoopFullUnrollPass on Loop at depth 3 containing: %l0.0.1.1<header>
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; CHECK-CHILDREN-NOT: LoopFullUnrollPass
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;
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; When we revisit children, we also revisit the current loop.
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; CHECK-CHILDREN: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0<header>
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; CHECK-CHILDREN-NOT: LoopFullUnrollPass
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;
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; Revisit the children of the outer loop that are part of the epilogue.
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;
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; CHECK: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0.1.epil<header>
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; CHECK-NOT: LoopFullUnrollPass
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; CHECK: LoopFullUnrollPass on Loop at depth 2 containing: %l0.0.0.epil<header>
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; CHECK-NOT: LoopFullUnrollPass
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l0.latch:
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br label %l0
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; CHECK: LoopFullUnrollPass on Loop at depth 1 containing: %l0<header>
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; CHECK-NOT: LoopFullUnrollPass
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exit:
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ret void
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}
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!1 = !{!1, !2}
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!2 = !{!"llvm.loop.unroll.count", i32 2}
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