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
76 lines
3.8 KiB
LLVM
76 lines
3.8 KiB
LLVM
; RUN: opt < %s -S -loop-unroll -unroll-runtime -unroll-count=2 -unroll-runtime-epilog=true | FileCheck %s -check-prefix=EPILOG
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; RUN: opt < %s -S -loop-unroll -unroll-runtime -unroll-count=2 -unroll-runtime-epilog=false | FileCheck %s -check-prefix=PROLOG
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; RUN: opt < %s -S -passes='require<opt-remark-emit>,loop-unroll' -unroll-runtime -unroll-count=2 -unroll-runtime-epilog=true | FileCheck %s -check-prefix=EPILOG
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; RUN: opt < %s -S -passes='require<opt-remark-emit>,loop-unroll' -unroll-runtime -unroll-count=2 -unroll-runtime-epilog=false | FileCheck %s -check-prefix=PROLOG
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; This tests that setting the unroll count works
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; EPILOG: for.body.preheader:
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; EPILOG: br i1 %1, label %for.end.loopexit.unr-lcssa, label %for.body.preheader.new, !dbg [[PH_LOC:![0-9]+]]
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; EPILOG: for.body:
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; EPILOG: br i1 %niter.ncmp.1, label %for.end.loopexit.unr-lcssa.loopexit, label %for.body, !dbg [[PH_LOC]]
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; EPILOG-NOT: br i1 %niter.ncmp.2, label %for.end.loopexit{{.*}}, label %for.body
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; EPILOG: for.body.epil.preheader:
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; EPILOG: br label %for.body.epil, !dbg [[PH_LOC]]
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; EPILOG: for.body.epil:
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; EPILOG: br label %for.end.loopexit, !dbg [[EXIT_LOC:![0-9]+]]
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; EPILOG: for.end.loopexit:
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; EPILOG: br label %for.end, !dbg [[EXIT_LOC]]
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; EPILOG-DAG: [[PH_LOC]] = !DILocation(line: 102, column: 1, scope: !{{.*}})
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; EPILOG-DAG: [[EXIT_LOC]] = !DILocation(line: 103, column: 1, scope: !{{.*}})
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; PROLOG: for.body.preheader:
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; PROLOG: br {{.*}} label %for.body.prol.preheader, label %for.body.prol.loopexit, !dbg [[PH_LOC:![0-9]+]]
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; PROLOG: for.body.prol:
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; PROLOG: br label %for.body.prol.loopexit, !dbg [[PH_LOC:![0-9]+]]
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; PROLOG: for.body.prol.loopexit:
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; PROLOG: br {{.*}} label %for.end.loopexit, label %for.body.preheader.new, !dbg [[PH_LOC]]
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; PROLOG: for.body:
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; PROLOG: br i1 %exitcond.1, label %for.end.loopexit.unr-lcssa, label %for.body, !dbg [[PH_LOC]]
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; PROLOG-NOT: br i1 %exitcond.4, label %for.end.loopexit{{.*}}, label %for.body
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; PROLOG-DAG: [[PH_LOC]] = !DILocation(line: 102, column: 1, scope: !{{.*}})
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define i32 @test(i32* nocapture %a, i32 %n) nounwind uwtable readonly !dbg !6 {
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entry:
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%cmp1 = icmp eq i32 %n, 0, !dbg !7
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br i1 %cmp1, label %for.end, label %for.body, !dbg !7
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for.body: ; preds = %for.body, %entry
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%indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
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%sum.02 = phi i32 [ %add, %for.body ], [ 0, %entry ]
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%arrayidx = getelementptr inbounds i32, i32* %a, i64 %indvars.iv, !dbg !8
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%0 = load i32, i32* %arrayidx, align 4, !dbg !8
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%add = add nsw i32 %0, %sum.02, !dbg !8
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%indvars.iv.next = add i64 %indvars.iv, 1, !dbg !9
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%lftr.wideiv = trunc i64 %indvars.iv.next to i32, !dbg !9
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%exitcond = icmp eq i32 %lftr.wideiv, %n, !dbg !9
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br i1 %exitcond, label %for.end, label %for.body, !dbg !9
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for.end: ; preds = %for.body, %entry
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%sum.0.lcssa = phi i32 [ 0, %entry ], [ %add, %for.body ]
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ret i32 %sum.0.lcssa, !dbg !10
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}
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!llvm.module.flags = !{!0, !1, !2}
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!llvm.dbg.cu = !{!11}
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!0 = !{i32 2, !"Dwarf Version", i32 4}
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!1 = !{i32 2, !"Debug Info Version", i32 3}
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!2 = !{i32 1, !"PIC Level", i32 2}
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!3 = !{}
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!4 = !DISubroutineType(types: !3)
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!5 = !DIFile(filename: "test.cpp", directory: "/tmp")
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!6 = distinct !DISubprogram(name: "test", scope: !5, file: !5, line: 99, type: !4, isLocal: false, isDefinition: true, scopeLine: 100, flags: DIFlagPrototyped, isOptimized: false, unit: !11, retainedNodes: !3)
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!7 = !DILocation(line: 100, column: 1, scope: !6)
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!8 = !DILocation(line: 101, column: 1, scope: !6)
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!9 = !DILocation(line: 102, column: 1, scope: !6)
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!10 = !DILocation(line: 103, column: 1, scope: !6)
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!11 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang",
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file: !5,
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isOptimized: true, flags: "-O2",
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splitDebugFilename: "abc.debug", emissionKind: 2)
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