15ea016346
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 llvm-svn: 248633
121 lines
4.9 KiB
LLVM
121 lines
4.9 KiB
LLVM
; RUN: opt < %s -sample-profile -sample-profile-file=%S/Inputs/calls.prof | opt -analyze -branch-prob | FileCheck %s
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; Original C++ test case
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;
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; #include <stdio.h>
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;
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; int sum(int x, int y) {
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; return x + y;
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; }
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;
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; int main() {
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; int s, i = 0;
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; while (i++ < 20000 * 20000)
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; if (i != 100) s = sum(i, s); else s = 30;
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; printf("sum is %d\n", s);
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; return 0;
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; }
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;
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; Note that this test is missing the llvm.dbg.cu annotation. This emulates
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; the effect of the user having only used -fprofile-sample-use without
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; -gmlt when invoking the driver. In those cases, we need to track source
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; location information but we do not have to generate debug info in the
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; final binary.
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@.str = private unnamed_addr constant [11 x i8] c"sum is %d\0A\00", align 1
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; Function Attrs: nounwind uwtable
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define i32 @_Z3sumii(i32 %x, i32 %y) {
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entry:
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%x.addr = alloca i32, align 4
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%y.addr = alloca i32, align 4
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store i32 %x, i32* %x.addr, align 4
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store i32 %y, i32* %y.addr, align 4
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%0 = load i32, i32* %x.addr, align 4, !dbg !11
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%1 = load i32, i32* %y.addr, align 4, !dbg !11
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%add = add nsw i32 %0, %1, !dbg !11
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ret i32 %add, !dbg !11
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}
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; Function Attrs: uwtable
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define i32 @main() {
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entry:
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%retval = alloca i32, align 4
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%s = alloca i32, align 4
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%i = alloca i32, align 4
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store i32 0, i32* %retval
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store i32 0, i32* %i, align 4, !dbg !12
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br label %while.cond, !dbg !13
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while.cond: ; preds = %if.end, %entry
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%0 = load i32, i32* %i, align 4, !dbg !14
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%inc = add nsw i32 %0, 1, !dbg !14
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store i32 %inc, i32* %i, align 4, !dbg !14
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%cmp = icmp slt i32 %0, 400000000, !dbg !14
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br i1 %cmp, label %while.body, label %while.end, !dbg !14
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; CHECK: edge while.cond -> while.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
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; CHECK: edge while.cond -> while.end probability is 0x00000000 / 0x80000000 = 0.00%
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while.body: ; preds = %while.cond
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%1 = load i32, i32* %i, align 4, !dbg !16
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%cmp1 = icmp ne i32 %1, 100, !dbg !16
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br i1 %cmp1, label %if.then, label %if.else, !dbg !16
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; Without discriminator information, the profiler used to think that
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; both branches out of while.body had the same weight. In reality,
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; the edge while.body->if.then is taken most of the time.
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;
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; CHECK: edge while.body -> if.then probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
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; CHECK: edge while.body -> if.else probability is 0x00000000 / 0x80000000 = 0.00%
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if.then: ; preds = %while.body
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%2 = load i32, i32* %i, align 4, !dbg !18
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%3 = load i32, i32* %s, align 4, !dbg !18
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%call = call i32 @_Z3sumii(i32 %2, i32 %3), !dbg !18
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store i32 %call, i32* %s, align 4, !dbg !18
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br label %if.end, !dbg !18
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if.else: ; preds = %while.body
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store i32 30, i32* %s, align 4, !dbg !20
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br label %if.end
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if.end: ; preds = %if.else, %if.then
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br label %while.cond, !dbg !22
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while.end: ; preds = %while.cond
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%4 = load i32, i32* %s, align 4, !dbg !24
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%call2 = call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([11 x i8], [11 x i8]* @.str, i32 0, i32 0), i32 %4), !dbg !24
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ret i32 0, !dbg !25
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}
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declare i32 @printf(i8*, ...) #2
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!llvm.module.flags = !{!8, !9}
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!llvm.ident = !{!10}
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!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, producer: "clang version 3.5 ", isOptimized: false, emissionKind: 0, file: !1, enums: !2, retainedTypes: !2, subprograms: !3, globals: !2, imports: !2)
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!1 = !DIFile(filename: "calls.cc", directory: ".")
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!2 = !{}
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!3 = !{!4, !7}
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!4 = distinct !DISubprogram(name: "sum", line: 3, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 3, file: !1, scope: !5, type: !6, function: i32 (i32, i32)* @_Z3sumii, variables: !2)
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!5 = !DIFile(filename: "calls.cc", directory: ".")
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!6 = !DISubroutineType(types: !2)
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!7 = distinct !DISubprogram(name: "main", line: 7, isLocal: false, isDefinition: true, virtualIndex: 6, flags: DIFlagPrototyped, isOptimized: false, scopeLine: 7, file: !1, scope: !5, type: !6, function: i32 ()* @main, variables: !2)
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!8 = !{i32 2, !"Dwarf Version", i32 4}
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!9 = !{i32 1, !"Debug Info Version", i32 3}
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!10 = !{!"clang version 3.5 "}
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!11 = !DILocation(line: 4, scope: !4)
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!12 = !DILocation(line: 8, scope: !7)
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!13 = !DILocation(line: 9, scope: !7)
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!14 = !DILocation(line: 9, scope: !15)
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!15 = !DILexicalBlockFile(discriminator: 1, file: !1, scope: !7)
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!16 = !DILocation(line: 10, scope: !17)
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!17 = distinct !DILexicalBlock(line: 10, column: 0, file: !1, scope: !7)
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!18 = !DILocation(line: 10, scope: !19)
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!19 = !DILexicalBlockFile(discriminator: 1, file: !1, scope: !17)
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!20 = !DILocation(line: 10, scope: !21)
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!21 = !DILexicalBlockFile(discriminator: 2, file: !1, scope: !17)
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!22 = !DILocation(line: 10, scope: !23)
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!23 = !DILexicalBlockFile(discriminator: 3, file: !1, scope: !17)
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!24 = !DILocation(line: 11, scope: !7)
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!25 = !DILocation(line: 12, scope: !7)
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