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[FastISel][X86] - Add branch weights 

Add branch weights to branch instructions, so that the following passes can
optimize based on it (i.e. basic block ordering).

llvm-svn: 210863
This commit is contained in:
Juergen Ributzka 2014-06-13 00:45:11 +00:00
parent 030294e4c5
commit 454d374e37
3 changed files with 41 additions and 5 deletions
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8
llvm/lib/CodeGen/SelectionDAG/FastISel.cpp
View File

@ -42,6 +42,7 @@
#include "llvm/CodeGen/FastISel.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/Analysis/Loads.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
@ -981,7 +982,6 @@ FastISel::SelectInstruction(const Instruction *I) {
/// the CFG.
void
FastISel::FastEmitBranch(MachineBasicBlock *MSucc, DebugLoc DbgLoc) {
if (FuncInfo.MBB->getBasicBlock()->size() > 1 &&
FuncInfo.MBB->isLayoutSuccessor(MSucc)) {
// For more accurate line information if this is the only instruction
@ -992,7 +992,11 @@ FastISel::FastEmitBranch(MachineBasicBlock *MSucc, DebugLoc DbgLoc) {
TII.InsertBranch(*FuncInfo.MBB, MSucc, nullptr,
SmallVector<MachineOperand, 0>(), DbgLoc);
}
FuncInfo.MBB->addSuccessor(MSucc);
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(FuncInfo.MBB->getBasicBlock(),
MSucc->getBasicBlock());
FuncInfo.MBB->addSuccessor(MSucc, BranchWeight);
}
/// SelectFNeg - Emit an FNeg operation.

19
llvm/lib/Target/X86/X86FastISel.cpp
View File

@ -20,6 +20,7 @@
#include "X86RegisterInfo.h"
#include "X86Subtarget.h"
#include "X86TargetMachine.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/FastISel.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
@ -1206,7 +1207,11 @@ bool X86FastISel::X86SelectBranch(const Instruction *I) {
}
FastEmitBranch(FalseMBB, DbgLoc);
FuncInfo.MBB->addSuccessor(TrueMBB);
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(BI->getParent(),
TrueMBB->getBasicBlock());
FuncInfo.MBB->addSuccessor(TrueMBB, BranchWeight);
return true;
}
} else if (TruncInst *TI = dyn_cast<TruncInst>(BI->getCondition())) {
@ -1238,7 +1243,11 @@ bool X86FastISel::X86SelectBranch(const Instruction *I) {
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(JmpOpc))
.addMBB(TrueMBB);
FastEmitBranch(FalseMBB, DbgLoc);
FuncInfo.MBB->addSuccessor(TrueMBB);
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(BI->getParent(),
TrueMBB->getBasicBlock());
FuncInfo.MBB->addSuccessor(TrueMBB, BranchWeight);
return true;
}
}
@ -1255,7 +1264,11 @@ bool X86FastISel::X86SelectBranch(const Instruction *I) {
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(X86::JNE_4))
.addMBB(TrueMBB);
FastEmitBranch(FalseMBB, DbgLoc);
FuncInfo.MBB->addSuccessor(TrueMBB);
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(BI->getParent(),
TrueMBB->getBasicBlock());
FuncInfo.MBB->addSuccessor(TrueMBB, BranchWeight);
return true;
}

19
llvm/test/CodeGen/X86/fast-isel-branch_weights.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: llc < %s -mtriple=x86_64-apple-darwin10 | FileCheck %s
; RUN: llc < %s -fast-isel -fast-isel-abort -mtriple=x86_64-apple-darwin10 | FileCheck %s
; Test if the BBs are reordred according to their branch weights.
define i64 @branch_weights_test(i64 %a, i64 %b) {
; CHECK-LABEL: branch_weights_test
; CHECK-LABEL: success
; CHECK-LABEL: fail
%1 = icmp ult i64 %a, %b
br i1 %1, label %fail, label %success, !prof !0
fail:
ret i64 -1
success:
ret i64 0
}
!0 = metadata !{metadata !"branch_weights", i32 0, i32 2147483647}