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Fix PR13851: Preserve metadata for the unswitched branch 

This patch copies the metadata of the unswitched branch to the newly
crreated branch in loop unswitch pass.

llvm-svn: 240378
This commit is contained in:
Weiming Zhao 2015-06-23 05:31:09 +00:00
parent aac108a324
commit f1abad57da
2 changed files with 144 additions and 20 deletions
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87
llvm/lib/Transforms/Scalar/LoopUnswitch.cpp
View File

@ -43,6 +43,7 @@
#include "llvm/IR/Function.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
@ -195,10 +196,12 @@ namespace {
/// Update the appropriate Phi nodes as we do so.
void SplitExitEdges(Loop *L, const SmallVectorImpl<BasicBlock *> &ExitBlocks);
bool UnswitchIfProfitable(Value *LoopCond, Constant *Val);
bool UnswitchIfProfitable(Value *LoopCond, Constant *Val,
TerminatorInst *TI = nullptr);
void UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val,
BasicBlock *ExitBlock);
void UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L);
BasicBlock *ExitBlock, TerminatorInst *TI);
void UnswitchNontrivialCondition(Value *LIC, Constant *OnVal, Loop *L,
TerminatorInst *TI);
void RewriteLoopBodyWithConditionConstant(Loop *L, Value *LIC,
Constant *Val, bool isEqual);
@ -206,7 +209,8 @@ namespace {
void EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
BasicBlock *TrueDest,
BasicBlock *FalseDest,
Instruction *InsertPt);
Instruction *InsertPt,
TerminatorInst *TI);
void SimplifyCode(std::vector<Instruction*> &Worklist, Loop *L);
bool IsTrivialUnswitchCondition(Value *Cond, Constant **Val = nullptr,
@ -453,8 +457,8 @@ bool LoopUnswitch::processCurrentLoop() {
// unswitch on it if we desire.
Value *LoopCond = FindLIVLoopCondition(BI->getCondition(),
currentLoop, Changed);
if (LoopCond && UnswitchIfProfitable(LoopCond,
ConstantInt::getTrue(Context))) {
if (LoopCond &&
UnswitchIfProfitable(LoopCond, ConstantInt::getTrue(Context), TI)) {
++NumBranches;
return true;
}
@ -643,7 +647,8 @@ bool LoopUnswitch::IsTrivialUnswitchCondition(Value *Cond, Constant **Val,
/// UnswitchIfProfitable - We have found that we can unswitch currentLoop when
/// LoopCond == Val to simplify the loop. If we decide that this is profitable,
/// unswitch the loop, reprocess the pieces, then return true.
bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val) {
bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val,
TerminatorInst *TI) {
Function *F = loopHeader->getParent();
Constant *CondVal = nullptr;
BasicBlock *ExitBlock = nullptr;
@ -651,7 +656,7 @@ bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val) {
if (IsTrivialUnswitchCondition(LoopCond, &CondVal, &ExitBlock)) {
// If the condition is trivial, always unswitch. There is no code growth
// for this case.
UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, ExitBlock);
UnswitchTrivialCondition(currentLoop, LoopCond, CondVal, ExitBlock, TI);
return true;
}
@ -661,7 +666,7 @@ bool LoopUnswitch::UnswitchIfProfitable(Value *LoopCond, Constant *Val) {
if (OptimizeForSize || F->hasFnAttribute(Attribute::OptimizeForSize))
return false;
UnswitchNontrivialCondition(LoopCond, Val, currentLoop);
UnswitchNontrivialCondition(LoopCond, Val, currentLoop, TI);
return true;
}
@ -685,25 +690,65 @@ static Loop *CloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM,
return New;
}
static void copyMetadata(Instruction *DstInst, const Instruction *SrcInst,
bool Swapped) {
if (!SrcInst || !SrcInst->hasMetadata())
return;
SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
SrcInst->getAllMetadata(MDs);
for (auto &MD : MDs) {
switch (MD.first) {
default:
break;
case LLVMContext::MD_prof:
if (Swapped && MD.second->getNumOperands() == 3 &&
isa<MDString>(MD.second->getOperand(0))) {
MDString *MDName = cast<MDString>(MD.second->getOperand(0));
if (MDName->getString() == "branch_weights") {
auto *ValT = cast_or_null<ConstantAsMetadata>(
MD.second->getOperand(1))->getValue();
auto *ValF = cast_or_null<ConstantAsMetadata>(
MD.second->getOperand(2))->getValue();
assert(ValT && ValF && "Invalid Operands of branch_weights");
auto NewMD =
MDBuilder(DstInst->getParent()->getContext())
.createBranchWeights(cast<ConstantInt>(ValF)->getZExtValue(),
cast<ConstantInt>(ValT)->getZExtValue());
MD.second = NewMD;
}
}
// fallthrough.
case LLVMContext::MD_dbg:
DstInst->setMetadata(MD.first, MD.second);
}
}
}
/// EmitPreheaderBranchOnCondition - Emit a conditional branch on two values
/// if LIC == Val, branch to TrueDst, otherwise branch to FalseDest. Insert the
/// code immediately before InsertPt.
void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
BasicBlock *TrueDest,
BasicBlock *FalseDest,
Instruction *InsertPt) {
Instruction *InsertPt,
TerminatorInst *TI) {
// Insert a conditional branch on LIC to the two preheaders. The original
// code is the true version and the new code is the false version.
Value *BranchVal = LIC;
bool Swapped = false;
if (!isa<ConstantInt>(Val) ||
Val->getType() != Type::getInt1Ty(LIC->getContext()))
BranchVal = new ICmpInst(InsertPt, ICmpInst::ICMP_EQ, LIC, Val);
else if (Val != ConstantInt::getTrue(Val->getContext()))
else if (Val != ConstantInt::getTrue(Val->getContext())) {
// We want to enter the new loop when the condition is true.
std::swap(TrueDest, FalseDest);
Swapped = true;
}
// Insert the new branch.
BranchInst *BI = BranchInst::Create(TrueDest, FalseDest, BranchVal, InsertPt);
copyMetadata(BI, TI, Swapped);
// If either edge is critical, split it. This helps preserve LoopSimplify
// form for enclosing loops.
@ -717,13 +762,14 @@ void LoopUnswitch::EmitPreheaderBranchOnCondition(Value *LIC, Constant *Val,
/// where the path through the loop that doesn't execute its body has no
/// side-effects), unswitch it. This doesn't involve any code duplication, just
/// moving the conditional branch outside of the loop and updating loop info.
void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond,
Constant *Val,
BasicBlock *ExitBlock) {
void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond, Constant *Val,
BasicBlock *ExitBlock,
TerminatorInst *TI) {
DEBUG(dbgs() << "loop-unswitch: Trivial-Unswitch loop %"
<< loopHeader->getName() << " [" << L->getBlocks().size()
<< " blocks] in Function " << L->getHeader()->getParent()->getName()
<< " on cond: " << *Val << " == " << *Cond << "\n");
<< loopHeader->getName() << " [" << L->getBlocks().size()
<< " blocks] in Function "
<< L->getHeader()->getParent()->getName() << " on cond: " << *Val
<< " == " << *Cond << "\n");
// First step, split the preheader, so that we know that there is a safe place
// to insert the conditional branch. We will change loopPreheader to have a
@ -744,7 +790,7 @@ void LoopUnswitch::UnswitchTrivialCondition(Loop *L, Value *Cond,
// Okay, now we have a position to branch from and a position to branch to,
// insert the new conditional branch.
EmitPreheaderBranchOnCondition(Cond, Val, NewExit, NewPH,
loopPreheader->getTerminator());
loopPreheader->getTerminator(), TI);
LPM->deleteSimpleAnalysisValue(loopPreheader->getTerminator(), L);
loopPreheader->getTerminator()->eraseFromParent();
@ -780,7 +826,7 @@ void LoopUnswitch::SplitExitEdges(Loop *L,
/// to unswitch when LIC equal Val. Split it into loop versions and test the
/// condition outside of either loop. Return the loops created as Out1/Out2.
void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
Loop *L) {
Loop *L, TerminatorInst *TI) {
Function *F = loopHeader->getParent();
DEBUG(dbgs() << "loop-unswitch: Unswitching loop %"
<< loopHeader->getName() << " [" << L->getBlocks().size()
@ -897,7 +943,8 @@ void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
"Preheader splitting did not work correctly!");
// Emit the new branch that selects between the two versions of this loop.
EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR);
EmitPreheaderBranchOnCondition(LIC, Val, NewBlocks[0], LoopBlocks[0], OldBR,
TI);
LPM->deleteSimpleAnalysisValue(OldBR, L);
OldBR->eraseFromParent();

77
llvm/test/Transforms/LoopUnswitch/2015-06-17-Metadata.ll Normal file
View File

@ -0,0 +1,77 @@
;RUN: opt -loop-unswitch -simplifycfg -S < %s | FileCheck %s
define i32 @foo(i32 %a, i32 %b) {
;CHECK-LABEL: foo
entry:
br label %for.body.lr.ph
for.body.lr.ph: ; preds = %entry
%cmp0 = icmp sgt i32 %b, 0
br i1 %cmp0, label %for.body, label %for.cond.cleanup
for.body: ; preds = %for.inc, %for.body.lr.ph
%inc.i = phi i32 [ 0, %for.body.lr.ph ], [ %inc, %for.inc ]
%mul.i = phi i32 [ 3, %for.body.lr.ph ], [ %mul.p, %for.inc ]
%add.i = phi i32 [ %a, %for.body.lr.ph ], [ %add.p, %for.inc ]
%cmp1 = icmp eq i32 %a, 12345
br i1 %cmp1, label %if.then, label %if.else, !prof !0
; CHECK: %cmp1 = icmp eq i32 %a, 12345
; CHECK-NEXT: br i1 %cmp1, label %if.then.us, label %if.else, !prof !0
if.then: ; preds = %for.body
; CHECK: if.then.us:
; CHECK: add nsw i32 %{{.*}}, 123
; CHECK: %exitcond.us = icmp eq i32 %inc.us, %b
; CHECK: br i1 %exitcond.us, label %for.cond.cleanup, label %if.then.us
%add = add nsw i32 %add.i, 123
br label %for.inc
if.else: ; preds = %for.body
%mul = mul nsw i32 %mul.i, %b
br label %for.inc
; CHECK: if.else:
; CHECK: %mul = mul nsw i32 %mul.i, %b
; CHECK: %inc = add nuw nsw i32 %inc.i, 1
; CHECK: %exitcond = icmp eq i32 %inc, %b
; CHECK: br i1 %exitcond, label %for.cond.cleanup, label %if.else
for.inc: ; preds = %if.then, %if.else
%mul.p = phi i32 [ %b, %if.then ], [ %mul, %if.else ]
%add.p = phi i32 [ %add, %if.then ], [ %a, %if.else ]
%inc = add nuw nsw i32 %inc.i, 1
%exitcond = icmp eq i32 %inc, %b
br i1 %exitcond, label %for.cond.cleanup, label %for.body
for.cond.cleanup: ; preds = %for.inc, %for.body.lr.ph
%t2 = phi i32 [ %b, %for.body.lr.ph ], [ %mul.p, %for.inc ]
%t1 = phi i32 [ %a, %for.body.lr.ph ], [ %add.p, %for.inc ]
%add3 = add nsw i32 %t2, %t1
ret i32 %add3
}
define void @foo_swapped(i32 %a, i32 %b) {
;CHECK-LABEL: foo_swapped
entry:
br label %for.body
;CHECK: entry:
;CHECK-NEXT: %cmp1 = icmp eq i32 1, 2
;CHECK-NEXT: br i1 %cmp1, label %for.body, label %for.cond.cleanup.split, !prof !1
;CHECK: for.body:
for.body: ; preds = %for.inc, %entry
%inc.i = phi i32 [ 0, %entry ], [ %inc, %if.then ]
%add.i = phi i32 [ 100, %entry ], [ %add, %if.then ]
%inc = add nuw nsw i32 %inc.i, 1
%cmp1 = icmp eq i32 1, 2
br i1 %cmp1, label %if.then, label %for.cond.cleanup, !prof !0
if.then: ; preds = %for.body
%add = add nsw i32 %a, %add.i
%exitcond = icmp eq i32 %inc, %b
br i1 %exitcond, label %for.cond.cleanup, label %for.body
for.cond.cleanup: ; preds = %for.inc, %for.body.lr.ph, %for.body
ret void
}
!0 = !{!"branch_weights", i32 64, i32 4}
;CHECK: !0 = !{!"branch_weights", i32 64, i32 4}
;CHECK: !1 = !{!"branch_weights", i32 4, i32 64}