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Do not simplifyLatch for loops where hoisting increments couldresult in extra live range interferance

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220872 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Yi Jiang 2014-10-29 20:19:47 +00:00
parent 3262c451c4
commit a5ca5d9f82
3 changed files with 34 additions and 7 deletions
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33
lib/Transforms/Scalar/LoopRotation.cpp
View File

@ -194,8 +194,13 @@ static void RewriteUsesOfClonedInstructions(BasicBlock *OrigHeader,
/// heuristics. We handle a single arithmetic instruction along with any type
/// conversions.
static bool shouldSpeculateInstrs(BasicBlock::iterator Begin,
BasicBlock::iterator End) {
BasicBlock::iterator End, Loop *L) {
bool seenIncrement = false;
bool MultiExitLoop = false;
if (!L->getExitingBlock())
MultiExitLoop = true;
for (BasicBlock::iterator I = Begin; I != End; ++I) {
if (!isSafeToSpeculativelyExecute(I))
@ -219,11 +224,33 @@ static bool shouldSpeculateInstrs(BasicBlock::iterator Begin,
case Instruction::Xor:
case Instruction::Shl:
case Instruction::LShr:
case Instruction::AShr:
case Instruction::AShr: {
Value *IVOpnd = nullptr;
if (isa<ConstantInt>(I->getOperand(0)))
IVOpnd = I->getOperand(1);
if (isa<ConstantInt>(I->getOperand(1))) {
if (IVOpnd)
return false;
IVOpnd = I->getOperand(0);
}
// If increment operand is used outside of the loop, this speculation
// could cause extra live range interference.
if (MultiExitLoop && IVOpnd) {
for (User *UseI : IVOpnd->users()) {
auto *UserInst = cast<Instruction>(UseI);
if (!L->contains(UserInst))
return false;
}
}
if (seenIncrement)
return false;
seenIncrement = true;
break;
}
case Instruction::Trunc:
case Instruction::ZExt:
case Instruction::SExt:
@ -259,7 +286,7 @@ bool LoopRotate::simplifyLoopLatch(Loop *L) {
if (!BI)
return false;
if (!shouldSpeculateInstrs(Latch->begin(), Jmp))
if (!shouldSpeculateInstrs(Latch->begin(), Jmp, L))
return false;
DEBUG(dbgs() << "Folding loop latch " << Latch->getName() << " into "

6
test/Transforms/LoopRotate/dbgvalue.ll
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@ -46,9 +46,9 @@ define void @FindFreeHorzSeg(i64 %startCol, i64 %row, i64* %rowStart) {
; CHECK-LABEL: define void @FindFreeHorzSeg(
; CHECK: %dec = add
; CHECK-NEXT: tail call void @llvm.dbg.value
; CHECK-NEXT: br i1 %tobool, label %for.cond, label %[[LOOP_EXIT:[^,]*]]
; CHECK: [[LOOP_EXIT]]:
; CHECK-NEXT: phi i64 [ %{{[^,]*}}, %{{[^,]*}} ]
; CHECK: %cmp = icmp
; CHECK: br i1 %cmp
; CHECK: phi i64 [ %{{[^,]*}}, %{{[^,]*}} ]
; CHECK-NEXT: br label %for.end

2
test/Transforms/LoopRotate/simplifylatch.ll
View File

@ -4,7 +4,7 @@
@mode_table = global [4 x i32] zeroinitializer ; <[4 x i32]*> [#uses=1]
; CHECK-LABEL: @f(
; CHECK-NOT: bb4
; CHECK-NOT: bb:
define i8 @f() {
entry:
tail call i32 @fegetround( ) ; <i32>:0 [#uses=1]