and extload's. If they are implemented as zero-extend, or implicitly
zero-extend, then this can enable more demanded bits optimizations. e.g.
define void @foo(i16* %ptr, i32 %a) nounwind {
entry:
%tmp1 = icmp ult i32 %a, 100
br i1 %tmp1, label %bb1, label %bb2
bb1:
%tmp2 = load i16* %ptr, align 2
br label %bb2
bb2:
%tmp3 = phi i16 [ 0, %entry ], [ %tmp2, %bb1 ]
%cmp = icmp ult i16 %tmp3, 24
br i1 %cmp, label %bb3, label %exit
bb3:
call void @bar() nounwind
br label %exit
exit:
ret void
}
This compiles to the followings before:
push {lr}
mov r2, #0
cmp r1, #99
bhi LBB0_2
@ BB#1: @ %bb1
ldrh r2, [r0]
LBB0_2: @ %bb2
uxth r0, r2
cmp r0, #23
bhi LBB0_4
@ BB#3: @ %bb3
bl _bar
LBB0_4: @ %exit
pop {lr}
bx lr
The uxth is not needed since ldrh implicitly zero-extend the high bits. With
this change it's eliminated.
rdar://
12771555
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169459
91177308-0d34-0410-b5e6-
96231b3b80d8
const SelectionDAG &DAG,
unsigned Depth = 0) const;
+ /// computeMaskedBitsForAnyExtend - Since each target implement ANY_EXTEND
+ /// and ExtLoad nodes specifically, let the target determine which of the bits
+ /// specified in Mask are known to be either zero or one and return them in
+ /// the KnownZero/KnownOne bitsets.
+ virtual void computeMaskedBitsForAnyExtend(const SDValue Op,
+ APInt &KnownZero,
+ APInt &KnownOne,
+ const SelectionDAG &DAG,
+ unsigned Depth = 0) const;
+
/// ComputeNumSignBitsForTargetNode - This method can be implemented by
/// targets that want to expose additional information about sign bits to the
/// DAG Combiner.
KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - MemBits);
} else if (const MDNode *Ranges = LD->getRanges()) {
computeMaskedBitsLoad(*Ranges, KnownZero);
+ } else if (ISD::isEXTLoad(Op.getNode())) {
+ TLI.computeMaskedBitsForAnyExtend(Op, KnownZero, KnownOne, *this, Depth);
}
return;
}
return;
}
case ISD::ANY_EXTEND: {
- EVT InVT = Op.getOperand(0).getValueType();
- unsigned InBits = InVT.getScalarType().getSizeInBits();
- KnownZero = KnownZero.trunc(InBits);
- KnownOne = KnownOne.trunc(InBits);
- ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
- KnownZero = KnownZero.zext(BitWidth);
- KnownOne = KnownOne.zext(BitWidth);
+ TLI.computeMaskedBitsForAnyExtend(Op, KnownZero, KnownOne, *this, Depth);
return;
}
case ISD::TRUNCATE: {
KnownZero = KnownOne = APInt(KnownOne.getBitWidth(), 0);
}
+void TargetLowering::computeMaskedBitsForAnyExtend(const SDValue Op,
+ APInt &KnownZero,
+ APInt &KnownOne,
+ const SelectionDAG &DAG,
+ unsigned Depth) const {
+ unsigned BitWidth = Op.getValueType().getScalarType().getSizeInBits();
+ if (Op.getOpcode() == ISD::ANY_EXTEND) {
+ EVT InVT = Op.getOperand(0).getValueType();
+ unsigned InBits = InVT.getScalarType().getSizeInBits();
+ KnownZero = KnownZero.trunc(InBits);
+ KnownOne = KnownOne.trunc(InBits);
+ DAG.ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
+ KnownZero = KnownZero.zext(BitWidth);
+ KnownOne = KnownOne.zext(BitWidth);
+ return;
+ } else if (ISD::isEXTLoad(Op.getNode())) {
+ KnownZero = KnownOne = APInt(BitWidth, 0);
+ return;
+ }
+
+ assert(0 && "Expecting an ANY_EXTEND or extload!");
+}
+
+
/// ComputeNumSignBitsForTargetNode - This method can be implemented by
/// targets that want to expose additional information about sign bits to the
/// DAG Combiner.
}
}
+void ARMTargetLowering::computeMaskedBitsForAnyExtend(const SDValue Op,
+ APInt &KnownZero,
+ APInt &KnownOne,
+ const SelectionDAG &DAG,
+ unsigned Depth) const {
+ unsigned BitWidth = Op.getValueType().getScalarType().getSizeInBits();
+ if (Op.getOpcode() == ISD::ANY_EXTEND) {
+ // Implemented as a zero_extend.
+ EVT InVT = Op.getOperand(0).getValueType();
+ unsigned InBits = InVT.getScalarType().getSizeInBits();
+ KnownZero = KnownZero.trunc(InBits);
+ KnownOne = KnownOne.trunc(InBits);
+ DAG.ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
+ KnownZero = KnownZero.zext(BitWidth);
+ KnownOne = KnownOne.zext(BitWidth);
+ APInt NewBits = APInt::getHighBitsSet(BitWidth, BitWidth - InBits);
+ KnownZero |= NewBits;
+ return;
+ } else if (ISD::isEXTLoad(Op.getNode())) {
+ // Implemented as zextloads.
+ LoadSDNode *LD = cast<LoadSDNode>(Op);
+ EVT VT = LD->getMemoryVT();
+ unsigned MemBits = VT.getScalarType().getSizeInBits();
+ KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - MemBits);
+ return;
+ }
+
+ assert(0 && "Expecting an ANY_EXTEND or extload!");
+}
+
//===----------------------------------------------------------------------===//
// ARM Inline Assembly Support
//===----------------------------------------------------------------------===//
const SelectionDAG &DAG,
unsigned Depth) const;
+ virtual void computeMaskedBitsForAnyExtend(const SDValue Op,
+ APInt &KnownZero,
+ APInt &KnownOne,
+ const SelectionDAG &DAG,
+ unsigned Depth) const;
virtual bool ExpandInlineAsm(CallInst *CI) const;
}
}
+void X86TargetLowering::computeMaskedBitsForAnyExtend(const SDValue Op,
+ APInt &KnownZero,
+ APInt &KnownOne,
+ const SelectionDAG &DAG,
+ unsigned Depth) const {
+ unsigned BitWidth = Op.getValueType().getScalarType().getSizeInBits();
+ if (Op.getOpcode() == ISD::ANY_EXTEND) {
+ // Implemented as a zero_extend except for i16 -> i32
+ EVT InVT = Op.getOperand(0).getValueType();
+ unsigned InBits = InVT.getScalarType().getSizeInBits();
+ KnownZero = KnownZero.trunc(InBits);
+ KnownOne = KnownOne.trunc(InBits);
+ DAG.ComputeMaskedBits(Op.getOperand(0), KnownZero, KnownOne, Depth+1);
+ KnownZero = KnownZero.zext(BitWidth);
+ KnownOne = KnownOne.zext(BitWidth);
+ if (BitWidth != 32 || InBits != 16) {
+ APInt NewBits = APInt::getHighBitsSet(BitWidth, BitWidth - InBits);
+ KnownZero |= NewBits;
+ }
+ return;
+ } else if (ISD::isEXTLoad(Op.getNode())) {
+ // Implemented as zextloads or implicitly zero-extended (i32 -> i64)
+ LoadSDNode *LD = cast<LoadSDNode>(Op);
+ EVT VT = LD->getMemoryVT();
+ unsigned MemBits = VT.getScalarType().getSizeInBits();
+ KnownZero |= APInt::getHighBitsSet(BitWidth, BitWidth - MemBits);
+ return;
+ }
+
+ assert(0 && "Expecting an ANY_EXTEND or extload!");
+}
+
unsigned X86TargetLowering::ComputeNumSignBitsForTargetNode(SDValue Op,
unsigned Depth) const {
// SETCC_CARRY sets the dest to ~0 for true or 0 for false.
const SelectionDAG &DAG,
unsigned Depth = 0) const;
+ virtual void computeMaskedBitsForAnyExtend(const SDValue Op,
+ APInt &KnownZero,
+ APInt &KnownOne,
+ const SelectionDAG &DAG,
+ unsigned Depth) const;
+
// ComputeNumSignBitsForTargetNode - Determine the number of bits in the
// operation that are sign bits.
virtual unsigned ComputeNumSignBitsForTargetNode(SDValue Op,
--- /dev/null
+; RUN: llc < %s -march=arm | FileCheck %s
+; rdar://12771555
+
+define void @foo(i16* %ptr, i32 %a) nounwind {
+entry:
+; CHECK: foo:
+ %tmp1 = icmp ult i32 %a, 100
+ br i1 %tmp1, label %bb1, label %bb2
+bb1:
+; CHECK: %bb1
+; CHECK: ldrh
+ %tmp2 = load i16* %ptr, align 2
+ br label %bb2
+bb2:
+; CHECK-NOT: uxth
+; CHECK: cmp
+ %tmp3 = phi i16 [ 0, %entry ], [ %tmp2, %bb1 ]
+ %cmp = icmp ult i16 %tmp3, 24
+ br i1 %cmp, label %bb3, label %exit
+bb3:
+ call void @bar() nounwind
+ br label %exit
+exit:
+ ret void
+}
+
+declare void @bar ()