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We are missing opportunites to use ldm. Take code like this:

Browse Source 
void t(int *cp0, int *cp1, int *dp, int fmd) {
  int c0, c1, d0, d1, d2, d3;
  c0 = (*cp0++ & 0xffff) | ((*cp1++ << 16) & 0xffff0000);
  c1 = (*cp0++ & 0xffff) | ((*cp1++ << 16) & 0xffff0000);
  /* ... */
}

It code gens into something pretty bad. But with this change (analogous to the
X86 back-end), it will use ldm and generate few instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106693 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Bill Wendling 2010-06-23 23:00:16 +00:00
parent 8ff72b5344
commit 4b722108e2
3 changed files with 126 additions and 3 deletions
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101
lib/Target/ARM/ARMBaseInstrInfo.cpp
View File

@ -1306,6 +1306,107 @@ bool ARMBaseInstrInfo::produceSameValue(const MachineInstr *MI0,
return MI0->isIdenticalTo(MI1, MachineInstr::IgnoreVRegDefs);
}
/// areLoadsFromSameBasePtr - This is used by the pre-regalloc scheduler to
/// determine if two loads are loading from the same base address. It should
/// only return true if the base pointers are the same and the only differences
/// between the two addresses is the offset. It also returns the offsets by
/// reference.
bool ARMBaseInstrInfo::areLoadsFromSameBasePtr(SDNode *Load1, SDNode *Load2,
int64_t &Offset1,
int64_t &Offset2) const {
// Don't worry about Thumb: just ARM and Thumb2.
if (Subtarget.isThumb1Only()) return false;
if (!Load1->isMachineOpcode() || !Load2->isMachineOpcode())
return false;
switch (Load1->getMachineOpcode()) {
default:
return false;
case ARM::LDR:
case ARM::LDRB:
case ARM::LDRD:
case ARM::LDRH:
case ARM::LDRSB:
case ARM::LDRSH:
case ARM::VLDRD:
case ARM::VLDRS:
case ARM::t2LDRi8:
case ARM::t2LDRDi8:
case ARM::t2LDRSHi8:
case ARM::t2LDRi12:
case ARM::t2LDRSHi12:
break;
}
switch (Load2->getMachineOpcode()) {
default:
return false;
case ARM::LDR:
case ARM::LDRB:
case ARM::LDRD:
case ARM::LDRH:
case ARM::LDRSB:
case ARM::LDRSH:
case ARM::VLDRD:
case ARM::VLDRS:
case ARM::t2LDRi8:
case ARM::t2LDRDi8:
case ARM::t2LDRSHi8:
case ARM::t2LDRi12:
case ARM::t2LDRSHi12:
break;
}
// Check if base addresses and chain operands match.
if (Load1->getOperand(0) != Load2->getOperand(0) ||
Load1->getOperand(4) != Load2->getOperand(4))
return false;
// Index should be Reg0.
if (Load1->getOperand(3) != Load2->getOperand(3))
return false;
// Determine the offsets.
if (isa<ConstantSDNode>(Load1->getOperand(1)) &&
isa<ConstantSDNode>(Load2->getOperand(1))) {
Offset1 = cast<ConstantSDNode>(Load1->getOperand(1))->getSExtValue();
Offset2 = cast<ConstantSDNode>(Load2->getOperand(1))->getSExtValue();
return true;
}
return false;
}
/// shouldScheduleLoadsNear - This is a used by the pre-regalloc scheduler to
/// determine (in conjuction with areLoadsFromSameBasePtr) if two loads should
/// be scheduled togther. On some targets if two loads are loading from
/// addresses in the same cache line, it's better if they are scheduled
/// together. This function takes two integers that represent the load offsets
/// from the common base address. It returns true if it decides it's desirable
/// to schedule the two loads together. "NumLoads" is the number of loads that
/// have already been scheduled after Load1.
bool ARMBaseInstrInfo::shouldScheduleLoadsNear(SDNode *Load1, SDNode *Load2,
int64_t Offset1, int64_t Offset2,
unsigned NumLoads) const {
// Don't worry about Thumb: just ARM and Thumb2.
if (Subtarget.isThumb1Only()) return false;
assert(Offset2 > Offset1);
if ((Offset2 - Offset1) / 8 > 64)
return false;
if (Load1->getMachineOpcode() != Load2->getMachineOpcode())
return false; // FIXME: overly conservative?
// Four loads in a row should be sufficient.
if (NumLoads >= 3)
return false;
return true;
}
bool ARMBaseInstrInfo::isSchedulingBoundary(const MachineInstr *MI,
const MachineBasicBlock *MBB,
const MachineFunction &MF) const {

20
lib/Target/ARM/ARMBaseInstrInfo.h
View File

@ -320,6 +320,26 @@ public:
virtual bool produceSameValue(const MachineInstr *MI0,
const MachineInstr *MI1) const;
/// areLoadsFromSameBasePtr - This is used by the pre-regalloc scheduler to
/// determine if two loads are loading from the same base address. It should
/// only return true if the base pointers are the same and the only
/// differences between the two addresses is the offset. It also returns the
/// offsets by reference.
virtual bool areLoadsFromSameBasePtr(SDNode *Load1, SDNode *Load2,
int64_t &Offset1, int64_t &Offset2)const;
/// shouldScheduleLoadsNear - This is a used by the pre-regalloc scheduler to
/// determine (in conjuction with areLoadsFromSameBasePtr) if two loads should
/// be scheduled togther. On some targets if two loads are loading from
/// addresses in the same cache line, it's better if they are scheduled
/// together. This function takes two integers that represent the load offsets
/// from the common base address. It returns true if it decides it's desirable
/// to schedule the two loads together. "NumLoads" is the number of loads that
/// have already been scheduled after Load1.
virtual bool shouldScheduleLoadsNear(SDNode *Load1, SDNode *Load2,
int64_t Offset1, int64_t Offset2,
unsigned NumLoads) const;
virtual bool isSchedulingBoundary(const MachineInstr *MI,
const MachineBasicBlock *MBB,
const MachineFunction &MF) const;

8
test/CodeGen/ARM/lsr-on-unrolled-loops.ll
View File

@ -626,9 +626,11 @@ bb24: ; preds = %bb23
; LSR should use count-down iteration to avoid requiring the trip count
; in a register, and it shouldn't require any reloads here.
; CHECK: subs r3, #1
; CHECK-NEXT: cmp r3, #0
; CHECK-NEXT: bne.w
; CHECK: @ %bb24
; CHECK-NEXT: @ in Loop: Header=BB1_1 Depth=1
; CHECK-NEXT: sub{{.*}} [[REGISTER:r[0-9]+]], #1
; CHECK-NEXT: cmp{{.*}} [[REGISTER]], #0
; CHECK-NEXT: bne.w
%92 = icmp eq i32 %tmp81, %indvar78 ; <i1> [#uses=1]
%indvar.next79 = add i32 %indvar78, 1 ; <i32> [#uses=1]