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archived-llvm/test/Transforms/SampleProfile/fnptr.ll
Cong Hou fed6bd8617 Use fixed-point representation for BranchProbability. 
BranchProbability now is represented by its numerator and denominator in uint32_t type. This patch changes this representation into a fixed point that is represented by the numerator in uint32_t type and a constant denominator 1<<31. This is quite similar to the representation of BlockMass in BlockFrequencyInfoImpl.h. There are several pros and cons of this change:

Pros:

1. It uses only a half space of the current one.
2. Some operations are much faster like plus, subtraction, comparison, and scaling by an integer.

Cons:

1. Constructing a probability using arbitrary numerator and denominator needs additional calculations.
2. It is a little less precise than before as we use a fixed denominator. For example, 1 - 1/3 may not be exactly identical to 1 / 3 (this will lead to many BranchProbability unit test failures). This should not matter when we only use it for branch probability. If we use it like a rational value for some precise calculations we may need another construct like ValueRatio.

One important reason for this change is that we propose to store branch probabilities instead of edge weights in MachineBasicBlock. We also want clients to use probability instead of weight when adding successors to a MBB. The current BranchProbability has more space which may be a concern.

Differential revision: http://reviews.llvm.org/D12603



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248633 91177308-0d34-0410-b5e6-96231b3b80d8
2015-09-25 23:09:59 +00:00

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; The two profiles used in this test are the same but encoded in different
; formats. This checks that we produce the same profile annotations regardless
; of the profile format.
;
; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/fnptr.prof | opt -analyze -branch-prob | FileCheck %s
; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/fnptr.binprof | opt -analyze -branch-prob | FileCheck %s
; CHECK: edge for.body3 -> if.then probability is 0x1a4f3959 / 0x80000000 = 20.55%
; CHECK: edge for.body3 -> if.else probability is 0x65b0c6a7 / 0x80000000 = 79.45%
; CHECK: edge for.inc -> for.inc12 probability is 0x33d4a4c1 / 0x80000000 = 40.49%
; CHECK: edge for.inc -> for.body3 probability is 0x4c2b5b3f / 0x80000000 = 59.51%
; CHECK: edge for.inc12 -> for.end14 probability is 0x3f06d04e / 0x80000000 = 49.24%
; CHECK: edge for.inc12 -> for.cond1.preheader probability is 0x40f92fb2 / 0x80000000 = 50.76%
; Original C++ test case.
;
; #include <stdlib.h>
; #include <math.h>
; #include <stdio.h>
;
; #define N 10000
; #define M 6000
;
; double foo(int x) {
; return x * sin((double)x);
; }
;
; double bar(int x) {
; return x - cos((double)x);
; }
;
; int main() {
; double (*fptr)(int);
; double S = 0;
; for (int i = 0; i < N; i++)
; for (int j = 0; j < M; j++) {
; fptr = (rand() % 100 < 30) ? foo : bar;
; if (rand() % 100 < 10)
; S += (*fptr)(i + j * 300);
; else
; S += (*fptr)(i - j / 840);
; }
; printf("S = %lf\n", S);
; return 0;
; }
@.str = private unnamed_addr constant [9 x i8] c"S = %lf\0A\00", align 1
define double @_Z3fooi(i32 %x) #0 {
entry:
%conv = sitofp i32 %x to double, !dbg !2
%call = tail call double @sin(double %conv) #3, !dbg !8
%mul = fmul double %conv, %call, !dbg !8
ret double %mul, !dbg !8
}
declare double @sin(double) #1
define double @_Z3bari(i32 %x) #0 {
entry:
%conv = sitofp i32 %x to double, !dbg !9
%call = tail call double @cos(double %conv) #3, !dbg !11
%sub = fsub double %conv, %call, !dbg !11
ret double %sub, !dbg !11
}
declare double @cos(double) #1
define i32 @main() #2 {
entry:
br label %for.cond1.preheader, !dbg !12
for.cond1.preheader: ; preds = %for.inc12, %entry
%i.025 = phi i32 [ 0, %entry ], [ %inc13, %for.inc12 ]
%S.024 = phi double [ 0.000000e+00, %entry ], [ %S.2.lcssa, %for.inc12 ]
br label %for.body3, !dbg !14
for.body3: ; preds = %for.inc, %for.cond1.preheader
%j.023 = phi i32 [ 0, %for.cond1.preheader ], [ %inc, %for.inc ]
%S.122 = phi double [ %S.024, %for.cond1.preheader ], [ %S.2, %for.inc ]
%call = tail call i32 @rand() #3, !dbg !15
%rem = srem i32 %call, 100, !dbg !15
%cmp4 = icmp slt i32 %rem, 30, !dbg !15
%_Z3fooi._Z3bari = select i1 %cmp4, double (i32)* @_Z3fooi, double (i32)* @_Z3bari, !dbg !15
%call5 = tail call i32 @rand() #3, !dbg !16
%rem6 = srem i32 %call5, 100, !dbg !16
%cmp7 = icmp slt i32 %rem6, 10, !dbg !16
br i1 %cmp7, label %if.then, label %if.else, !dbg !16, !prof !17
if.then: ; preds = %for.body3
%mul = mul nsw i32 %j.023, 300, !dbg !18
%add = add nsw i32 %mul, %i.025, !dbg !18
%call8 = tail call double %_Z3fooi._Z3bari(i32 %add), !dbg !18
br label %for.inc, !dbg !18
if.else: ; preds = %for.body3
%div = sdiv i32 %j.023, 840, !dbg !19
%sub = sub nsw i32 %i.025, %div, !dbg !19
%call10 = tail call double %_Z3fooi._Z3bari(i32 %sub), !dbg !19
br label %for.inc
for.inc: ; preds = %if.then, %if.else
%call8.pn = phi double [ %call8, %if.then ], [ %call10, %if.else ]
%S.2 = fadd double %S.122, %call8.pn, !dbg !18
%inc = add nsw i32 %j.023, 1, !dbg !20
%exitcond = icmp eq i32 %j.023, 5999, !dbg !14
br i1 %exitcond, label %for.inc12, label %for.body3, !dbg !14, !prof !21
for.inc12: ; preds = %for.inc
%S.2.lcssa = phi double [ %S.2, %for.inc ]
%inc13 = add nsw i32 %i.025, 1, !dbg !22
%exitcond26 = icmp eq i32 %i.025, 9999, !dbg !12
br i1 %exitcond26, label %for.end14, label %for.cond1.preheader, !dbg !12, !prof !23
for.end14: ; preds = %for.inc12
%S.2.lcssa.lcssa = phi double [ %S.2.lcssa, %for.inc12 ]
%call15 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([9 x i8], [9 x i8]* @.str, i64 0, i64 0), double %S.2.lcssa.lcssa), !dbg !24
ret i32 0, !dbg !25
}
; Function Attrs: nounwind
declare i32 @rand() #1
; Function Attrs: nounwind
declare i32 @printf(i8* nocapture readonly, ...) #1
!llvm.module.flags = !{!0}
!llvm.ident = !{!1}
!0 = !{i32 2, !"Debug Info Version", i32 3}
!1 = !{!"clang version 3.6.0 "}
!2 = !DILocation(line: 9, column: 3, scope: !3)
!3 = distinct !DISubprogram(name: "foo", line: 8, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 8, file: !4, scope: !5, type: !6, function: double (i32)* @_Z3fooi, variables: !7)
!4 = !DIFile(filename: "fnptr.cc", directory: ".")
!5 = !DIFile(filename: "fnptr.cc", directory: ".")
!6 = !DISubroutineType(types: !7)
!7 = !{}
!8 = !DILocation(line: 9, column: 14, scope: !3)
!9 = !DILocation(line: 13, column: 3, scope: !10)
!10 = distinct !DISubprogram(name: "bar", line: 12, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 12, file: !4, scope: !5, type: !6, function: double (i32)* @_Z3bari, variables: !7)
!11 = !DILocation(line: 13, column: 14, scope: !10)
!12 = !DILocation(line: 19, column: 3, scope: !13)
!13 = distinct !DISubprogram(name: "main", line: 16, isLocal: false, isDefinition: true, flags: DIFlagPrototyped, isOptimized: true, scopeLine: 16, file: !4, scope: !5, type: !6, function: i32 ()* @main, variables: !7)
!14 = !DILocation(line: 20, column: 5, scope: !13)
!15 = !DILocation(line: 21, column: 15, scope: !13)
!16 = !DILocation(line: 22, column: 11, scope: !13)
!17 = !{!"branch_weights", i32 534, i32 2064}
!18 = !DILocation(line: 23, column: 14, scope: !13)
!19 = !DILocation(line: 25, column: 14, scope: !13)
!20 = !DILocation(line: 20, column: 28, scope: !13)
!21 = !{!"branch_weights", i32 0, i32 1075}
!22 = !DILocation(line: 19, column: 26, scope: !13)
!23 = !{!"branch_weights", i32 0, i32 534}
!24 = !DILocation(line: 27, column: 3, scope: !13)
!25 = !DILocation(line: 28, column: 3, scope: !13)
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