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Dehao Chen a75059ebaa Encode duplication factor from loop vectorization and loop unrolling to discriminator.
Summary:
This patch starts the implementation as discuss in the following RFC: http://lists.llvm.org/pipermail/llvm-dev/2016-October/106532.html

When optimization duplicates code that will scale down the execution count of a basic block, we will record the duplication factor as part of discriminator so that the offline process tool can find the duplication factor and collect the accurate execution frequency of the corresponding source code. Two important optimization that fall into this category is loop vectorization and loop unroll. This patch records the duplication factor for these 2 optimizations.

The recording will be guarded by a flag encode-duplication-in-discriminators, which is off by default.

Reviewers: probinson, aprantl, davidxl, hfinkel, echristo

Reviewed By: hfinkel

Subscribers: mehdi_amini, anemet, mzolotukhin, llvm-commits

Differential Revision: https://reviews.llvm.org/D26420

llvm-svn: 294782
2017-02-10 21:09:07 +00:00

73 lines
3.1 KiB
LLVM

; RUN: opt < %s -add-discriminators -S | FileCheck %s
; RUN: opt < %s -passes=add-discriminators -S | FileCheck %s
; Discriminator support for multiple CFG paths on the same line.
;
; void foo(int i) {
; int x;
; if (i < 10) x = i; else x = -i;
; }
;
; The two stores inside the if-then-else line must have different discriminator
; values.
define void @foo(i32 %i) #0 !dbg !4 {
entry:
%i.addr = alloca i32, align 4
%x = alloca i32, align 4
store i32 %i, i32* %i.addr, align 4
%0 = load i32, i32* %i.addr, align 4, !dbg !10
%cmp = icmp slt i32 %0, 10, !dbg !10
br i1 %cmp, label %if.then, label %if.else, !dbg !10
if.then: ; preds = %entry
%1 = load i32, i32* %i.addr, align 4, !dbg !10
; CHECK: %1 = load i32, i32* %i.addr, align 4, !dbg ![[THEN:[0-9]+]]
store i32 %1, i32* %x, align 4, !dbg !10
; CHECK: store i32 %1, i32* %x, align 4, !dbg ![[THEN]]
br label %if.end, !dbg !10
; CHECK: br label %if.end, !dbg ![[THEN]]
if.else: ; preds = %entry
%2 = load i32, i32* %i.addr, align 4, !dbg !10
; CHECK: %2 = load i32, i32* %i.addr, align 4, !dbg ![[ELSE:[0-9]+]]
%sub = sub nsw i32 0, %2, !dbg !10
; CHECK: %sub = sub nsw i32 0, %2, !dbg ![[ELSE]]
store i32 %sub, i32* %x, align 4, !dbg !10
; CHECK: store i32 %sub, i32* %x, align 4, !dbg ![[ELSE]]
br label %if.end
if.end: ; preds = %if.else, %if.then
ret void, !dbg !12
}
attributes #0 = { nounwind uwtable "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
!llvm.dbg.cu = !{!0}
!llvm.module.flags = !{!7, !8}
!llvm.ident = !{!9}
!0 = distinct !DICompileUnit(language: DW_LANG_C99, producer: "clang version 3.5 (trunk 199750) (llvm/trunk 199751)", isOptimized: false, emissionKind: NoDebug, file: !1, enums: !2, retainedTypes: !2, globals: !2, imports: !2)
!1 = !DIFile(filename: "multiple.c", directory: ".")
!2 = !{}
!4 = distinct !DISubprogram(name: "foo", line: 1, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, unit: !0, scopeLine: 1, file: !1, scope: !5, type: !6, variables: !2)
!5 = !DIFile(filename: "multiple.c", directory: ".")
!6 = !DISubroutineType(types: !{null, !13})
!13 = !DIBasicType(encoding: DW_ATE_signed, name: "int", size: 32, align: 32)
!7 = !{i32 2, !"Dwarf Version", i32 4}
!8 = !{i32 1, !"Debug Info Version", i32 3}
!9 = !{!"clang version 3.5 (trunk 199750) (llvm/trunk 199751)"}
!10 = !DILocation(line: 3, scope: !11)
!11 = distinct !DILexicalBlock(line: 3, column: 0, file: !1, scope: !4)
!12 = !DILocation(line: 4, scope: !4)
; CHECK: ![[THEN]] = !DILocation(line: 3, scope: ![[THENBLOCK:[0-9]+]])
; CHECK: ![[THENBLOCK]] = !DILexicalBlockFile(scope: ![[SCOPE:[0-9]+]],{{.*}} discriminator: 2)
; CHECK: ![[ELSE]] = !DILocation(line: 3, scope: ![[ELSEBLOCK:[0-9]+]])
; CHECK: ![[ELSEBLOCK]] = !DILexicalBlockFile(scope: ![[SCOPE]],{{.*}} discriminator: 4)