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[FastISel][AArch64] Add branch weights.

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

Fixes <rdar://problem/17887137>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214537 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Juergen Ributzka 2014-08-01 18:39:24 +00:00
parent fff7ba35a3
commit 3d253a3f80
2 changed files with 57 additions and 5 deletions
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43
lib/Target/AArch64/AArch64FastISel.cpp
View File

@ -17,6 +17,7 @@
#include "AArch64Subtarget.h"
#include "AArch64TargetMachine.h"
#include "MCTargetDesc/AArch64AddressingModes.h"
#include "llvm/Analysis/BranchProbabilityInfo.h"
#include "llvm/CodeGen/CallingConvLower.h"
#include "llvm/CodeGen/FastISel.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
@ -843,7 +844,13 @@ bool AArch64FastISel::SelectBranch(const Instruction *I) {
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(AArch64::Bcc))
.addImm(CC)
.addMBB(TBB);
FuncInfo.MBB->addSuccessor(TBB);
// Obtain the branch weight and add the TrueBB to the successor list.
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(BI->getParent(),
TBB->getBasicBlock());
FuncInfo.MBB->addSuccessor(TBB, BranchWeight);
FastEmitBranch(FBB, DbgLoc);
return true;
@ -881,7 +888,14 @@ bool AArch64FastISel::SelectBranch(const Instruction *I) {
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(AArch64::Bcc))
.addImm(CC)
.addMBB(TBB);
FuncInfo.MBB->addSuccessor(TBB);
// Obtain the branch weight and add the TrueBB to the successor list.
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(BI->getParent(),
TBB->getBasicBlock());
FuncInfo.MBB->addSuccessor(TBB, BranchWeight);
FastEmitBranch(FBB, DbgLoc);
return true;
}
@ -891,7 +905,13 @@ bool AArch64FastISel::SelectBranch(const Instruction *I) {
MachineBasicBlock *Target = (Imm == 0) ? FBB : TBB;
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(AArch64::B))
.addMBB(Target);
FuncInfo.MBB->addSuccessor(Target);
// Obtain the branch weight and add the target to the successor list.
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(BI->getParent(),
Target->getBasicBlock());
FuncInfo.MBB->addSuccessor(Target, BranchWeight);
return true;
} else if (foldXALUIntrinsic(CC, I, BI->getCondition())) {
// Fake request the condition, otherwise the intrinsic might be completely
@ -904,7 +924,13 @@ bool AArch64FastISel::SelectBranch(const Instruction *I) {
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(AArch64::Bcc))
.addImm(CC)
.addMBB(TBB);
FuncInfo.MBB->addSuccessor(TBB);
// Obtain the branch weight and add the TrueBB to the successor list.
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(BI->getParent(),
TBB->getBasicBlock());
FuncInfo.MBB->addSuccessor(TBB, BranchWeight);
FastEmitBranch(FBB, DbgLoc);
return true;
@ -935,7 +961,14 @@ bool AArch64FastISel::SelectBranch(const Instruction *I) {
BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc, TII.get(AArch64::Bcc))
.addImm(CC)
.addMBB(TBB);
FuncInfo.MBB->addSuccessor(TBB);
// Obtain the branch weight and add the TrueBB to the successor list.
uint32_t BranchWeight = 0;
if (FuncInfo.BPI)
BranchWeight = FuncInfo.BPI->getEdgeWeight(BI->getParent(),
TBB->getBasicBlock());
FuncInfo.MBB->addSuccessor(TBB, BranchWeight);
FastEmitBranch(FBB, DbgLoc);
return true;
}

19
test/CodeGen/AArch64/fast-isel-branch_weights.ll Normal file
View File

@ -0,0 +1,19 @@
; RUN: llc -mtriple=arm64-apple-darwin -aarch64-atomic-cfg-tidy=0 < %s | FileCheck %s
; RUN: llc -mtriple=arm64-apple-darwin -aarch64-atomic-cfg-tidy=0 -fast-isel -fast-isel-abort < %s | 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}