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PGO branch weight: fix PR18752.

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Fix a bug triggered in IfConverterTriangle when CvtBB has multiple predecessors
by getting the weights before removing a successor.

llvm-svn: 200958
This commit is contained in:
Manman Ren 2014-02-07 00:38:56 +00:00
parent f2f14a2d43
commit 5fdca739ee
2 changed files with 66 additions and 5 deletions
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9
lib/CodeGen/IfConversion.cpp
View File

@ -1180,12 +1180,14 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
DontKill.clear();
bool HasEarlyExit = CvtBBI->FalseBB != NULL;
uint64_t CvtNext = 0, CvtFalse = 0, SumWeight = 0;
uint64_t CvtNext = 0, CvtFalse = 0, BBNext = 0, BBCvt = 0, SumWeight = 0;
uint32_t WeightScale = 0;
if (HasEarlyExit) {
// Get weights before modifying CvtBBI->BB.
// Get weights before modifying CvtBBI->BB and BBI.BB.
CvtNext = MBPI->getEdgeWeight(CvtBBI->BB, NextBBI->BB);
CvtFalse = MBPI->getEdgeWeight(CvtBBI->BB, CvtBBI->FalseBB);
BBNext = MBPI->getEdgeWeight(BBI.BB, NextBBI->BB);
BBCvt = MBPI->getEdgeWeight(BBI.BB, CvtBBI->BB);
SumWeight = MBPI->getSumForBlock(CvtBBI->BB, WeightScale);
}
if (CvtBBI->BB->pred_size() > 1) {
@ -1222,9 +1224,6 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI, IfcvtKind Kind) {
// New_Weight(BBI.BB, CvtBBI->FalseBB) =
// Weight(BBI.BB, CvtBBI->BB) * Weight(CvtBBI->BB, CvtBBI->FalseBB)
uint64_t BBNext = MBPI->getEdgeWeight(BBI.BB, NextBBI->BB);
uint64_t BBCvt = MBPI->getEdgeWeight(BBI.BB, CvtBBI->BB);
uint64_t NewNext = BBNext * SumWeight + (BBCvt * CvtNext) / WeightScale;
uint64_t NewFalse = (BBCvt * CvtFalse) / WeightScale;
// We need to scale down all weights of BBI.BB to fit uint32_t.

62
test/CodeGen/ARM/ifcvt-branch-weight-bug.ll Normal file
View File

@ -0,0 +1,62 @@
; RUN: llc < %s -mtriple=armv4t--linux-androideabi -print-machineinstrs=if-converter -o /dev/null 2>&1 | FileCheck %s
; Fix a bug triggered in IfConverterTriangle when CvtBB has multiple
; predecessors.
; PR18752
%classK = type { i8, %classF }
%classF = type { i8 }
%classL = type { %classG, i32, i32 }
%classG = type { %classL* }
%classM2 = type { %classL }
define zeroext i1 @test(%classK* %this, %classM2* nocapture readnone %p1, %classM2* nocapture readnone %p2) align 2 {
entry:
br i1 undef, label %for.end, label %for.body
; Before if conversion, we have
; for.body -> lor.lhs.false.i (62)
; -> for.cond.backedge (62)
; lor.lhs.false.i -> for.cond.backedge (1048575)
; -> cond.false.i (1)
; Afer if conversion, we have
; for.body -> for.cond.backedge (130023362)
; -> cond.false.i (62)
; CHECK: BB#1: derived from LLVM BB %for.body
; CHECK: Successors according to CFG: BB#2(130023362) BB#4(62)
for.body:
br i1 undef, label %for.cond.backedge, label %lor.lhs.false.i
for.cond.backedge:
%tobool = icmp eq %classL* undef, null
br i1 %tobool, label %for.end, label %for.body
lor.lhs.false.i:
%tobool.i.i7 = icmp eq i32 undef, 0
br i1 %tobool.i.i7, label %for.cond.backedge, label %cond.false.i
cond.false.i:
call void @_Z3fn1v()
unreachable
for.end:
br i1 undef, label %if.else.i.i, label %if.then.i.i
if.then.i.i:
store %classL* null, %classL** undef, align 4
br label %_ZN1M6spliceEv.exit
if.else.i.i:
store %classL* null, %classL** null, align 4
br label %_ZN1M6spliceEv.exit
_ZN1M6spliceEv.exit:
%LIS = getelementptr inbounds %classK* %this, i32 0, i32 1
call void @_ZN1F10handleMoveEb(%classF* %LIS, i1 zeroext false)
unreachable
}
declare %classL* @_ZN1M1JI1LS1_EcvPS1_Ev(%classM2*)
declare void @_ZN1F10handleMoveEb(%classF*, i1 zeroext)
declare void @_Z3fn1v()
!0 = metadata !{metadata !"clang version 3.5"}