2017-02-21 08:12:38 +08:00
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; RUN: llc < %s | FileCheck %s
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;
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; The test code is generated from the following source code:
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;
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; 1 extern int bar(int x);
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; 2
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; 3 int foo(int *begin, int *end) {
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; 4 int *i;
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; 5 int ret = 0;
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; 6 for (
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; 7 i = begin ;
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; 8 i != end ;
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; 9 i++)
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; 10 {
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; 11 ret += bar(*i);
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; 12 }
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; 13 return ret;
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; 14 }
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;
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; CHECK: # %entry
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; CHECK-NOT: # %for.body
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; CHECK: .loc 1 6 3
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; CHECK-NEXT: je [[BB:.LBB[^ ]+]]
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[CodeGen] Add a new pass for PostRA sink
Summary:
This pass sinks COPY instructions into a successor block, if the COPY is not
used in the current block and the COPY is live-in to a single successor
(i.e., doesn't require the COPY to be duplicated). This avoids executing the
the copy on paths where their results aren't needed. This also exposes
additional opportunites for dead copy elimination and shrink wrapping.
These copies were either not handled by or are inserted after the MachineSink
pass. As an example of the former case, the MachineSink pass cannot sink
COPY instructions with allocatable source registers; for AArch64 these type
of copy instructions are frequently used to move function parameters (PhyReg)
into virtual registers in the entry block..
For the machine IR below, this pass will sink %w19 in the entry into its
successor (%bb.1) because %w19 is only live-in in %bb.1.
```
%bb.0:
%wzr = SUBSWri %w1, 1
%w19 = COPY %w0
Bcc 11, %bb.2
%bb.1:
Live Ins: %w19
BL @fun
%w0 = ADDWrr %w0, %w19
RET %w0
%bb.2:
%w0 = COPY %wzr
RET %w0
```
As we sink %w19 (CSR in AArch64) into %bb.1, the shrink-wrapping pass will be
able to see %bb.0 as a candidate.
With this change I observed 12% more shrink-wrapping candidate and 13% more dead copies deleted in spec2000/2006/2017 on AArch64.
Reviewers: qcolombet, MatzeB, thegameg, mcrosier, gberry, hfinkel, john.brawn, twoh, RKSimon, sebpop, kparzysz
Reviewed By: sebpop
Subscribers: evandro, sebpop, sfertile, aemerson, mgorny, javed.absar, kristof.beyls, llvm-commits
Differential Revision: https://reviews.llvm.org/D41463
llvm-svn: 328237
2018-03-23 04:06:47 +08:00
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; CHECK: [[BB]]:
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; CHECK: xorl %ebp, %ebp
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; CHECK-NEXT: .LBB{{.*}} # %for.end
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2017-02-21 08:12:38 +08:00
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target triple = "x86_64-unknown-linux-gnu"
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define i32 @foo(i32* readonly %begin, i32* readnone %end) !dbg !4 {
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entry:
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%cmp6 = icmp eq i32* %begin, %end, !dbg !9
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br i1 %cmp6, label %for.end, label %for.body.preheader, !dbg !12
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for.body.preheader: ; preds = %entry
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br label %for.body, !dbg !13
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for.body: ; preds = %for.body.preheader, %for.body
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%ret.08 = phi i32 [ %add, %for.body ], [ 0, %for.body.preheader ]
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%i.07 = phi i32* [ %incdec.ptr, %for.body ], [ %begin, %for.body.preheader ]
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%0 = load i32, i32* %i.07, align 4, !dbg !13, !tbaa !15
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%call = tail call i32 @bar(i32 %0), !dbg !19
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%add = add nsw i32 %call, %ret.08, !dbg !20
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%incdec.ptr = getelementptr inbounds i32, i32* %i.07, i64 1, !dbg !21
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%cmp = icmp eq i32* %incdec.ptr, %end, !dbg !9
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br i1 %cmp, label %for.end.loopexit, label %for.body, !dbg !12, !llvm.loop !22
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for.end.loopexit: ; preds = %for.body
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br label %for.end, !dbg !24
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for.end: ; preds = %for.end.loopexit, %entry
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%ret.0.lcssa = phi i32 [ 0, %entry ], [ %add, %for.end.loopexit ]
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ret i32 %ret.0.lcssa, !dbg !24
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}
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declare i32 @bar(i32)
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!llvm.dbg.cu = !{!0}
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!llvm.module.flags = !{!2, !3}
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!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, emissionKind: FullDebug)
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!1 = !DIFile(filename: "foo.c", directory: "b/")
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!2 = !{i32 2, !"Dwarf Version", i32 4}
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!3 = !{i32 2, !"Debug Info Version", i32 3}
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!4 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 3, type: !5, isLocal: false, isDefinition: true, scopeLine: 3, flags: DIFlagPrototyped, isOptimized: true, unit: !0)
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!5 = !DISubroutineType(types: !6)
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!6 = !{!7, !8, !8}
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!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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!8 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !7, size: 64)
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!9 = !DILocation(line: 8, column: 9, scope: !10)
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!10 = distinct !DILexicalBlock(scope: !11, file: !1, line: 6, column: 3)
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!11 = distinct !DILexicalBlock(scope: !4, file: !1, line: 6, column: 3)
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!12 = !DILocation(line: 6, column: 3, scope: !11)
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!13 = !DILocation(line: 11, column: 18, scope: !14)
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!14 = distinct !DILexicalBlock(scope: !10, file: !1, line: 10, column: 3)
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!15 = !{!16, !16, i64 0}
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!16 = !{!"int", !17, i64 0}
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!17 = !{!"omnipotent char", !18, i64 0}
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|
!18 = !{!"Simple C/C++ TBAA"}
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!19 = !DILocation(line: 11, column: 14, scope: !14)
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!20 = !DILocation(line: 11, column: 11, scope: !14)
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!21 = !DILocation(line: 9, column: 8, scope: !10)
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!22 = distinct !{!22, !12, !23}
|
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!23 = !DILocation(line: 12, column: 3, scope: !11)
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!24 = !DILocation(line: 13, column: 3, scope: !4)
|