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We need to control exponential behavior of loop-unswitch so we do not get run-away compilation. Suggested solution is to introduce a multiplier for an unswitch cost that makes cost prohibitive as soon as there are too many candidates and too many sibling loops (meaning we have already started duplicating loops by unswitching). It does solve the currently known problem with compile-time degradation (PR 39544). Tests are built on top of a recently implemented CHECK-COUNT-<num> FileCheck directives. Reviewed By: chandlerc, mkazantsev Differential Revision: https://reviews.llvm.org/D54223 llvm-svn: 347097
150 lines
5.6 KiB
LLVM
150 lines
5.6 KiB
LLVM
;
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; Here all the branches we unswitch are exiting from the inner loop.
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; That means we should not be getting exponential behavior on inner-loop
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; unswitch. In fact there should be just a single version of inner-loop,
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; with possibly some outer loop copies.
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;
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; There should be just a single copy of each loop when strictest mutiplier
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; candidates formula (unscaled candidates == 0) is enforced:
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; RUN: opt < %s -enable-nontrivial-unswitch -enable-unswitch-cost-multiplier=true \
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; RUN: -unswitch-num-initial-unscaled-candidates=0 -unswitch-siblings-toplevel-div=1 \
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; RUN: -passes='loop(unswitch),print<loops>' -disable-output 2>&1 | FileCheck %s --check-prefixes=LOOP1
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;
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; RUN: opt < %s -enable-nontrivial-unswitch -enable-unswitch-cost-multiplier=true \
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; RUN: -unswitch-num-initial-unscaled-candidates=0 -unswitch-siblings-toplevel-div=16 \
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; RUN: -passes='loop(unswitch),print<loops>' -disable-output 2>&1 | FileCheck %s --check-prefixes=LOOP1
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;
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;
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; When we relax the candidates part of a multiplier formula
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; (unscaled candidates == 2) we start getting some unswitches in outer loops,
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; which leads to siblings multiplier kicking in.
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;
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; RUN: opt < %s -enable-nontrivial-unswitch -enable-unswitch-cost-multiplier=true \
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; RUN: -unswitch-num-initial-unscaled-candidates=3 -unswitch-siblings-toplevel-div=1 \
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; RUN: -passes='loop(unswitch),print<loops>' -disable-output 2>&1 | \
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; RUN: sort -b | FileCheck %s --check-prefixes=LOOP-UNSCALE3-DIV1
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;
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; NB: sort -b is essential here and below, otherwise blanks might lead to different
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; order depending on locale.
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;
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; RUN: opt < %s -enable-nontrivial-unswitch -enable-unswitch-cost-multiplier=true \
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; RUN: -unswitch-num-initial-unscaled-candidates=3 -unswitch-siblings-toplevel-div=2 \
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; RUN: -passes='loop(unswitch),print<loops>' -disable-output 2>&1 | \
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; RUN: sort -b | FileCheck %s --check-prefixes=LOOP-UNSCALE3-DIV2
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;
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; With disabled cost-multiplier we get maximal possible amount of unswitches.
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;
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; RUN: opt < %s -enable-nontrivial-unswitch -enable-unswitch-cost-multiplier=false \
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; RUN: -passes='loop(unswitch),print<loops>' -disable-output 2>&1 | \
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; RUN: sort -b | FileCheck %s --check-prefixes=LOOP-MAX
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;
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; Single loop nest, not unswitched
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; LOOP1: Loop at depth 1 containing:
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; LOOP1-NOT: Loop at depth 1 containing:
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; LOOP1: Loop at depth 2 containing:
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; LOOP1-NOT: Loop at depth 2 containing:
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; LOOP1: Loop at depth 3 containing:
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; LOOP1-NOT: Loop at depth 3 containing:
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;
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; Half unswitched loop nests, with unscaled3 and div1 it gets less depth1 loops unswitched
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; since they have more cost.
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; LOOP-UNSCALE3-DIV1-COUNT-4: Loop at depth 1 containing:
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; LOOP-UNSCALE3-DIV1-NOT: Loop at depth 1 containing:
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; LOOP-UNSCALE3-DIV1-COUNT-1: Loop at depth 2 containing:
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; LOOP-UNSCALE3-DIV1-NOT: Loop at depth 2 containing:
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; LOOP-UNSCALE3-DIV1-COUNT-1: Loop at depth 3 containing:
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; LOOP-UNSCALE3-DIV1-NOT: Loop at depth 3 containing:
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;
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; Half unswitched loop nests, with unscaled3 and div2 it gets more depth1 loops unswitched
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; as div2 kicks in.
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; LOOP-UNSCALE3-DIV2-COUNT-6: Loop at depth 1 containing:
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; LOOP-UNSCALE3-DIV2-NOT: Loop at depth 1 containing:
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; LOOP-UNSCALE3-DIV2-COUNT-1: Loop at depth 2 containing:
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; LOOP-UNSCALE3-DIV2-NOT: Loop at depth 2 containing:
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; LOOP-UNSCALE3-DIV2-COUNT-1: Loop at depth 3 containing:
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; LOOP-UNSCALE3-DIV2-NOT: Loop at depth 3 containing:
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;
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; Maximally unswitched (copy of the outer loop per each condition)
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; LOOP-MAX-COUNT-6: Loop at depth 1 containing:
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; LOOP-MAX-NOT: Loop at depth 1 containing:
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; LOOP-MAX-COUNT-1: Loop at depth 2 containing:
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; LOOP-MAX-NOT: Loop at depth 2 containing:
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; LOOP-MAX-COUNT-1: Loop at depth 3 containing:
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; LOOP-MAX-NOT: Loop at depth 3 containing:
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declare void @bar()
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define void @loop_nested3_conds5(i32* %addr, i1 %c1, i1 %c2, i1 %c3, i1 %c4, i1 %c5) {
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entry:
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%addr1 = getelementptr i32, i32* %addr, i64 0
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%addr2 = getelementptr i32, i32* %addr, i64 1
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%addr3 = getelementptr i32, i32* %addr, i64 2
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br label %outer
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outer:
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%iv1 = phi i32 [0, %entry], [%iv1.next, %outer_latch]
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%iv1.next = add i32 %iv1, 1
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;; skip nontrivial unswitch
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call void @bar()
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br label %middle
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middle:
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%iv2 = phi i32 [0, %outer], [%iv2.next, %middle_latch]
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%iv2.next = add i32 %iv2, 1
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;; skip nontrivial unswitch
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call void @bar()
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br label %loop
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loop:
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%iv3 = phi i32 [0, %middle], [%iv3.next, %loop_latch]
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%iv3.next = add i32 %iv3, 1
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;; skip nontrivial unswitch
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call void @bar()
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br i1 %c1, label %loop_next1_left, label %outer_latch
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loop_next1_left:
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br label %loop_next1
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loop_next1_right:
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br label %loop_next1
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loop_next1:
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br i1 %c2, label %loop_next2_left, label %outer_latch
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loop_next2_left:
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br label %loop_next2
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loop_next2_right:
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br label %loop_next2
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loop_next2:
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br i1 %c3, label %loop_next3_left, label %outer_latch
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loop_next3_left:
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br label %loop_next3
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loop_next3_right:
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br label %loop_next3
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loop_next3:
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br i1 %c4, label %loop_next4_left, label %outer_latch
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loop_next4_left:
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br label %loop_next4
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loop_next4_right:
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br label %loop_next4
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loop_next4:
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br i1 %c5, label %loop_latch_left, label %outer_latch
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loop_latch_left:
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br label %loop_latch
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loop_latch_right:
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br label %loop_latch
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loop_latch:
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store volatile i32 0, i32* %addr1
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%test_loop = icmp slt i32 %iv3, 50
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br i1 %test_loop, label %loop, label %middle_latch
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middle_latch:
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store volatile i32 0, i32* %addr2
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%test_middle = icmp slt i32 %iv2, 50
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br i1 %test_middle, label %middle, label %outer_latch
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outer_latch:
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store volatile i32 0, i32* %addr3
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%test_outer = icmp slt i32 %iv1, 50
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br i1 %test_outer, label %outer, label %exit
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exit:
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ret void
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}
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