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Implement Jakob's suggestion on how to detect fall thought without calling

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AnalyzeBranch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@132981 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2011-06-14 06:08:32 +00:00
parent 79abd1c27c
commit f5b5c5156c
2 changed files with 20 additions and 13 deletions
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29
lib/CodeGen/AsmPrinter/AsmPrinter.cpp
View File

@ -1934,19 +1934,26 @@ isBlockOnlyReachableByFallthrough(const MachineBasicBlock *MBB) const {
if (Pred->empty())
return true;
// Otherwise, ask the backend.
const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
MachineBasicBlock *PredTBB = NULL, *PredFBB = NULL;
SmallVector<MachineOperand, 4> PredCond;
if (TII->AnalyzeBranch(*Pred, PredTBB, PredFBB, PredCond))
return false;
// Check the terminators in the previous blocks
for (MachineBasicBlock::iterator II = Pred->getFirstTerminator(),
IE = Pred->end(); II != IE; ++II) {
MachineInstr &MI = *II;
if (PredTBB == MBB || PredFBB == MBB)
return false;
// If it is not a simple branch, we are in a table somewhere.
if (!MI.getDesc().isBranch() || MI.getDesc().isIndirectBranch())
return false;
// This is a fall through if there is no conditions in the bb
// or if there is no explicit false branch.
return PredCond.empty() || !PredFBB;
// If we are the operands of one of the branches, this is not
// a fall through.
for (MachineInstr::mop_iterator OI = MI.operands_begin(),
OE = MI.operands_end(); OI != OE; ++OI) {
const MachineOperand& OP = *OI;
if (OP.isMBB() && OP.getMBB() == MBB)
return false;
}
}
return true;
}

4
test/CodeGen/Thumb2/machine-licm.ll
View File

@ -13,7 +13,7 @@ entry:
br i1 %0, label %return, label %bb.nph
bb.nph: ; preds = %entry
; CHECK: LBB0_1:
; CHECK: BB#1
; CHECK: movw r[[R2:[0-9]+]], :lower16:L_GV$non_lazy_ptr
; CHECK: movt r[[R2]], :upper16:L_GV$non_lazy_ptr
; CHECK: ldr{{(.w)?}} r[[R2b:[0-9]+]], [r[[R2]]
@ -21,7 +21,7 @@ bb.nph: ; preds = %entry
; CHECK: LBB0_2
; CHECK-NOT: LCPI0_0:
; PIC: LBB0_1:
; PIC: BB#1
; PIC: movw r[[R2:[0-9]+]], :lower16:(L_GV$non_lazy_ptr-(LPC0_0+4))
; PIC: movt r[[R2]], :upper16:(L_GV$non_lazy_ptr-(LPC0_0+4))
; PIC: add r[[R2]], pc