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llvm-mirror/test/Analysis/BranchProbabilityInfo/loop.ll
Cong Hou 3919ffc012 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

llvm-svn: 248633
2015-09-25 23:09:59 +00:00

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; Test the static branch probability heuristics for no-return functions.
; RUN: opt < %s -analyze -branch-prob | FileCheck %s
declare void @g1()
declare void @g2()
declare void @g3()
declare void @g4()
define void @test1(i32 %a, i32 %b) {
entry:
br label %do.body
; CHECK: edge entry -> do.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
do.body:
%i.0 = phi i32 [ 0, %entry ], [ %inc3, %do.end ]
call void @g1()
br label %do.body1
; CHECK: edge do.body -> do.body1 probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
do.body1:
%j.0 = phi i32 [ 0, %do.body ], [ %inc, %do.body1 ]
call void @g2()
%inc = add nsw i32 %j.0, 1
%cmp = icmp slt i32 %inc, %b
br i1 %cmp, label %do.body1, label %do.end
; CHECK: edge do.body1 -> do.body1 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge do.body1 -> do.end probability is 0x04000000 / 0x80000000 = 3.12%
do.end:
call void @g3()
%inc3 = add nsw i32 %i.0, 1
%cmp4 = icmp slt i32 %inc3, %a
br i1 %cmp4, label %do.body, label %do.end5
; CHECK: edge do.end -> do.body probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge do.end -> do.end5 probability is 0x04000000 / 0x80000000 = 3.12%
do.end5:
call void @g4()
ret void
}
define void @test2(i32 %a, i32 %b) {
entry:
%cmp9 = icmp sgt i32 %a, 0
br i1 %cmp9, label %for.body.lr.ph, label %for.end6
; CHECK: edge entry -> for.body.lr.ph probability is 0x50000000 / 0x80000000 = 62.50%
; CHECK: edge entry -> for.end6 probability is 0x30000000 / 0x80000000 = 37.50%
for.body.lr.ph:
%cmp27 = icmp sgt i32 %b, 0
br label %for.body
; CHECK: edge for.body.lr.ph -> for.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
for.body:
%i.010 = phi i32 [ 0, %for.body.lr.ph ], [ %inc5, %for.end ]
call void @g1()
br i1 %cmp27, label %for.body3, label %for.end
; CHECK: edge for.body -> for.body3 probability is 0x50000000 / 0x80000000 = 62.50%
; CHECK: edge for.body -> for.end probability is 0x30000000 / 0x80000000 = 37.50%
for.body3:
%j.08 = phi i32 [ %inc, %for.body3 ], [ 0, %for.body ]
call void @g2()
%inc = add nsw i32 %j.08, 1
%exitcond = icmp eq i32 %inc, %b
br i1 %exitcond, label %for.end, label %for.body3
; CHECK: edge for.body3 -> for.end probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge for.body3 -> for.body3 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
for.end:
call void @g3()
%inc5 = add nsw i32 %i.010, 1
%exitcond11 = icmp eq i32 %inc5, %a
br i1 %exitcond11, label %for.end6, label %for.body
; CHECK: edge for.end -> for.end6 probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge for.end -> for.body probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
for.end6:
call void @g4()
ret void
}
define void @test3(i32 %a, i32 %b, i32* %c) {
entry:
br label %do.body
; CHECK: edge entry -> do.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
do.body:
%i.0 = phi i32 [ 0, %entry ], [ %inc4, %if.end ]
call void @g1()
%0 = load i32, i32* %c, align 4
%cmp = icmp slt i32 %0, 42
br i1 %cmp, label %do.body1, label %if.end
; CHECK: edge do.body -> do.body1 probability is 0x40000000 / 0x80000000 = 50.00%
; CHECK: edge do.body -> if.end probability is 0x40000000 / 0x80000000 = 50.00%
do.body1:
%j.0 = phi i32 [ %inc, %do.body1 ], [ 0, %do.body ]
call void @g2()
%inc = add nsw i32 %j.0, 1
%cmp2 = icmp slt i32 %inc, %b
br i1 %cmp2, label %do.body1, label %if.end
; CHECK: edge do.body1 -> do.body1 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge do.body1 -> if.end probability is 0x04000000 / 0x80000000 = 3.12%
if.end:
call void @g3()
%inc4 = add nsw i32 %i.0, 1
%cmp5 = icmp slt i32 %inc4, %a
br i1 %cmp5, label %do.body, label %do.end6
; CHECK: edge if.end -> do.body probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge if.end -> do.end6 probability is 0x04000000 / 0x80000000 = 3.12%
do.end6:
call void @g4()
ret void
}
define void @test4(i32 %a, i32 %b, i32* %c) {
entry:
br label %do.body
; CHECK: edge entry -> do.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
do.body:
%i.0 = phi i32 [ 0, %entry ], [ %inc4, %do.end ]
call void @g1()
%0 = load i32, i32* %c, align 4
%cmp = icmp slt i32 %0, 42
br i1 %cmp, label %return, label %do.body1
; CHECK: edge do.body -> return probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge do.body -> do.body1 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
do.body1:
%j.0 = phi i32 [ %inc, %do.body1 ], [ 0, %do.body ]
call void @g2()
%inc = add nsw i32 %j.0, 1
%cmp2 = icmp slt i32 %inc, %b
br i1 %cmp2, label %do.body1, label %do.end
; CHECK: edge do.body1 -> do.body1 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge do.body1 -> do.end probability is 0x04000000 / 0x80000000 = 3.12%
do.end:
call void @g3()
%inc4 = add nsw i32 %i.0, 1
%cmp5 = icmp slt i32 %inc4, %a
br i1 %cmp5, label %do.body, label %do.end6
; CHECK: edge do.end -> do.body probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge do.end -> do.end6 probability is 0x04000000 / 0x80000000 = 3.12%
do.end6:
call void @g4()
br label %return
; CHECK: edge do.end6 -> return probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
return:
ret void
}
define void @test5(i32 %a, i32 %b, i32* %c) {
entry:
br label %do.body
; CHECK: edge entry -> do.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
do.body:
%i.0 = phi i32 [ 0, %entry ], [ %inc4, %do.end ]
call void @g1()
br label %do.body1
; CHECK: edge do.body -> do.body1 probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
do.body1:
%j.0 = phi i32 [ 0, %do.body ], [ %inc, %if.end ]
%0 = load i32, i32* %c, align 4
%cmp = icmp slt i32 %0, 42
br i1 %cmp, label %return, label %if.end
; CHECK: edge do.body1 -> return probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge do.body1 -> if.end probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
if.end:
call void @g2()
%inc = add nsw i32 %j.0, 1
%cmp2 = icmp slt i32 %inc, %b
br i1 %cmp2, label %do.body1, label %do.end
; CHECK: edge if.end -> do.body1 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge if.end -> do.end probability is 0x04000000 / 0x80000000 = 3.12%
do.end:
call void @g3()
%inc4 = add nsw i32 %i.0, 1
%cmp5 = icmp slt i32 %inc4, %a
br i1 %cmp5, label %do.body, label %do.end6
; CHECK: edge do.end -> do.body probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge do.end -> do.end6 probability is 0x04000000 / 0x80000000 = 3.12%
do.end6:
call void @g4()
br label %return
; CHECK: edge do.end6 -> return probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
return:
ret void
}
define void @test6(i32 %a, i32 %b, i32* %c) {
entry:
br label %do.body
; CHECK: edge entry -> do.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
do.body:
%i.0 = phi i32 [ 0, %entry ], [ %inc4, %do.end ]
call void @g1()
br label %do.body1
; CHECK: edge do.body -> do.body1 probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
do.body1:
%j.0 = phi i32 [ 0, %do.body ], [ %inc, %do.cond ]
call void @g2()
%0 = load i32, i32* %c, align 4
%cmp = icmp slt i32 %0, 42
br i1 %cmp, label %return, label %do.cond
; CHECK: edge do.body1 -> return probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge do.body1 -> do.cond probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
do.cond:
%inc = add nsw i32 %j.0, 1
%cmp2 = icmp slt i32 %inc, %b
br i1 %cmp2, label %do.body1, label %do.end
; CHECK: edge do.cond -> do.body1 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge do.cond -> do.end probability is 0x04000000 / 0x80000000 = 3.12%
do.end:
call void @g3()
%inc4 = add nsw i32 %i.0, 1
%cmp5 = icmp slt i32 %inc4, %a
br i1 %cmp5, label %do.body, label %do.end6
; CHECK: edge do.end -> do.body probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
; CHECK: edge do.end -> do.end6 probability is 0x04000000 / 0x80000000 = 3.12%
do.end6:
call void @g4()
br label %return
; CHECK: edge do.end6 -> return probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
return:
ret void
}
define void @test7(i32 %a, i32 %b, i32* %c) {
entry:
%cmp10 = icmp sgt i32 %a, 0
br i1 %cmp10, label %for.body.lr.ph, label %for.end7
; CHECK: edge entry -> for.body.lr.ph probability is 0x50000000 / 0x80000000 = 62.50%
; CHECK: edge entry -> for.end7 probability is 0x30000000 / 0x80000000 = 37.50%
for.body.lr.ph:
%cmp38 = icmp sgt i32 %b, 0
br label %for.body
; CHECK: edge for.body.lr.ph -> for.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
for.body:
%i.011 = phi i32 [ 0, %for.body.lr.ph ], [ %inc6, %for.inc5 ]
%0 = load i32, i32* %c, align 4
%cmp1 = icmp eq i32 %0, %i.011
br i1 %cmp1, label %for.inc5, label %if.end
; CHECK: edge for.body -> for.inc5 probability is 0x40000000 / 0x80000000 = 50.00%
; CHECK: edge for.body -> if.end probability is 0x40000000 / 0x80000000 = 50.00%
if.end:
call void @g1()
br i1 %cmp38, label %for.body4, label %for.end
; CHECK: edge if.end -> for.body4 probability is 0x50000000 / 0x80000000 = 62.50%
; CHECK: edge if.end -> for.end probability is 0x30000000 / 0x80000000 = 37.50%
for.body4:
%j.09 = phi i32 [ %inc, %for.body4 ], [ 0, %if.end ]
call void @g2()
%inc = add nsw i32 %j.09, 1
%exitcond = icmp eq i32 %inc, %b
br i1 %exitcond, label %for.end, label %for.body4
; CHECK: edge for.body4 -> for.end probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge for.body4 -> for.body4 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
for.end:
call void @g3()
br label %for.inc5
; CHECK: edge for.end -> for.inc5 probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
for.inc5:
%inc6 = add nsw i32 %i.011, 1
%exitcond12 = icmp eq i32 %inc6, %a
br i1 %exitcond12, label %for.end7, label %for.body
; CHECK: edge for.inc5 -> for.end7 probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge for.inc5 -> for.body probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
for.end7:
call void @g4()
ret void
}
define void @test8(i32 %a, i32 %b, i32* %c) {
entry:
%cmp18 = icmp sgt i32 %a, 0
br i1 %cmp18, label %for.body.lr.ph, label %for.end15
; CHECK: edge entry -> for.body.lr.ph probability is 0x50000000 / 0x80000000 = 62.50%
; CHECK: edge entry -> for.end15 probability is 0x30000000 / 0x80000000 = 37.50%
for.body.lr.ph:
%cmp216 = icmp sgt i32 %b, 0
%arrayidx5 = getelementptr inbounds i32, i32* %c, i64 1
%arrayidx9 = getelementptr inbounds i32, i32* %c, i64 2
br label %for.body
; CHECK: edge for.body.lr.ph -> for.body probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
for.body:
%i.019 = phi i32 [ 0, %for.body.lr.ph ], [ %inc14, %for.end ]
call void @g1()
br i1 %cmp216, label %for.body3, label %for.end
; CHECK: edge for.body -> for.body3 probability is 0x50000000 / 0x80000000 = 62.50%
; CHECK: edge for.body -> for.end probability is 0x30000000 / 0x80000000 = 37.50%
for.body3:
%j.017 = phi i32 [ 0, %for.body ], [ %inc, %for.inc ]
%0 = load i32, i32* %c, align 4
%cmp4 = icmp eq i32 %0, %j.017
br i1 %cmp4, label %for.inc, label %if.end
; CHECK: edge for.body3 -> for.inc probability is 0x40000000 / 0x80000000 = 50.00%
; CHECK: edge for.body3 -> if.end probability is 0x40000000 / 0x80000000 = 50.00%
if.end:
%1 = load i32, i32* %arrayidx5, align 4
%cmp6 = icmp eq i32 %1, %j.017
br i1 %cmp6, label %for.inc, label %if.end8
; CHECK: edge if.end -> for.inc probability is 0x40000000 / 0x80000000 = 50.00%
; CHECK: edge if.end -> if.end8 probability is 0x40000000 / 0x80000000 = 50.00%
if.end8:
%2 = load i32, i32* %arrayidx9, align 4
%cmp10 = icmp eq i32 %2, %j.017
br i1 %cmp10, label %for.inc, label %if.end12
; CHECK: edge if.end8 -> for.inc probability is 0x40000000 / 0x80000000 = 50.00%
; CHECK: edge if.end8 -> if.end12 probability is 0x40000000 / 0x80000000 = 50.00%
if.end12:
call void @g2()
br label %for.inc
; CHECK: edge if.end12 -> for.inc probability is 0x80000000 / 0x80000000 = 100.00% [HOT edge]
for.inc:
%inc = add nsw i32 %j.017, 1
%exitcond = icmp eq i32 %inc, %b
br i1 %exitcond, label %for.end, label %for.body3
; CHECK: edge for.inc -> for.end probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge for.inc -> for.body3 probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
for.end:
call void @g3()
%inc14 = add nsw i32 %i.019, 1
%exitcond20 = icmp eq i32 %inc14, %a
br i1 %exitcond20, label %for.end15, label %for.body
; CHECK: edge for.end -> for.end15 probability is 0x04000000 / 0x80000000 = 3.12%
; CHECK: edge for.end -> for.body probability is 0x7c000000 / 0x80000000 = 96.88% [HOT edge]
for.end15:
call void @g4()
ret void
}
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