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Prefer to expand mask for xor to -1, so we have a chance to turn it into a not.

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If it cannot be expanded, it will keep the old behaviour and try to shrink the constant.
Part of enhancement for PR2191.

llvm-svn: 49280
This commit is contained in:
Torok Edwin 2008-04-06 21:23:02 +00:00
parent 6c6b8a57f3
commit 34e6889671
2 changed files with 165 additions and 4 deletions
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23
lib/CodeGen/SelectionDAG/TargetLowering.cpp
View File

@ -657,10 +657,25 @@ bool TargetLowering::SimplifyDemandedBits(SDOperand Op,
}
// If the RHS is a constant, see if we can simplify it.
// FIXME: for XOR, we prefer to force bits to 1 if they will make a -1.
if (TLO.ShrinkDemandedConstant(Op, NewMask))
return true;
// for XOR, we prefer to force bits to 1 if they will make a -1.
// if we can't force bits, try to shrink constant
if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Op.getOperand(1))) {
APInt Expanded = C->getAPIntValue() | (~NewMask);
// if we can expand it to have all bits set, do it
if (Expanded.isAllOnesValue()) {
if (Expanded != C->getAPIntValue()) {
MVT::ValueType VT = Op.getValueType();
SDOperand New = TLO.DAG.getNode(Op.getOpcode(), VT, Op.getOperand(0),
TLO.DAG.getConstant(Expanded, VT));
return TLO.CombineTo(Op, New);
}
// if it already has all the bits set, nothing to change
// but don't shrink either!
} else if (TLO.ShrinkDemandedConstant(Op, NewMask)) {
return true;
}
}
KnownZero = KnownZeroOut;
KnownOne = KnownOneOut;
break;

146
test/CodeGen/X86/xor_not.ll Normal file
View File

@ -0,0 +1,146 @@
; RUN: llvm-as < %s | llc -march=x86 | grep not[lwb] | count 3
; RUN: llvm-as < %s | llc -march=x86-64 | grep not[lwb] | count 4
define i32 @test(i32 %a, i32 %b) nounwind {
entry:
%tmp1not = xor i32 %b, -2
%tmp3 = and i32 %tmp1not, %a
%tmp4 = lshr i32 %tmp3, 1
ret i32 %tmp4
}
define i32 @sum32(i32 %a, i32 %b) nounwind {
entry:
br label %bb
bb:
%b_addr.0 = phi i32 [ %b, %entry ], [ %tmp8, %bb ]
%a_addr.0 = phi i32 [ %a, %entry ], [ %tmp3, %bb ]
%tmp3 = xor i32 %a_addr.0, %b_addr.0
%tmp4not = xor i32 %tmp3, 2147483647
%tmp6 = and i32 %tmp4not, %b_addr.0
%tmp8 = shl i32 %tmp6, 1
%tmp10 = icmp eq i32 %tmp8, 0
br i1 %tmp10, label %bb12, label %bb
bb12:
ret i32 %tmp3
}
define i16 @sum16(i16 %a, i16 %b) nounwind {
entry:
br label %bb
bb:
%b_addr.0 = phi i16 [ %b, %entry ], [ %tmp8, %bb ]
%a_addr.0 = phi i16 [ %a, %entry ], [ %tmp3, %bb ]
%tmp3 = xor i16 %a_addr.0, %b_addr.0
%tmp4not = xor i16 %tmp3, 32767
%tmp6 = and i16 %tmp4not, %b_addr.0
%tmp8 = shl i16 %tmp6, 1
%tmp10 = icmp eq i16 %tmp8, 0
br i1 %tmp10, label %bb12, label %bb
bb12:
ret i16 %tmp3
}
define i8 @sum8(i8 %a, i8 %b) nounwind {
entry:
br label %bb
bb:
%b_addr.0 = phi i8 [ %b, %entry ], [ %tmp8, %bb ]
%a_addr.0 = phi i8 [ %a, %entry ], [ %tmp3, %bb ]
%tmp3 = xor i8 %a_addr.0, %b_addr.0
%tmp4not = xor i8 %tmp3, 127
%tmp6 = and i8 %tmp4not, %b_addr.0
%tmp8 = shl i8 %tmp6, 1
%tmp10 = icmp eq i8 %tmp8, 0
br i1 %tmp10, label %bb12, label %bb
bb12:
ret i8 %tmp3
}
define i32 @notransform(i32 %a, i32 %b) nounwind {
entry:
br label %bb
bb:
%b_addr.0 = phi i32 [ %b, %entry ], [ %tmp8, %bb ]
%a_addr.0 = phi i32 [ %a, %entry ], [ %tmp3, %bb ]
%tmp3 = xor i32 %a_addr.0, %b_addr.0
%tmp4not = xor i32 %tmp3, 2147483646
%tmp6 = and i32 %tmp4not, %b_addr.0
%tmp8 = shl i32 %tmp6, 1
%tmp10 = icmp eq i32 %tmp8, 0
br i1 %tmp10, label %bb12, label %bb
bb12:
ret i32 %tmp3
}
; RUN: llvm-as < %s | llc -march=x86 | grep not[lwb] | count 3
; RUN: llvm-as < %s | llc -march=x86-64 | grep not[lwb] | count 4
define i32 @test(i32 %a, i32 %b) nounwind {
entry:
%tmp1not = xor i32 %b, -2
%tmp3 = and i32 %tmp1not, %a
%tmp4 = lshr i32 %tmp3, 1
ret i32 %tmp4
}
define i32 @sum32(i32 %a, i32 %b) nounwind {
entry:
br label %bb
bb:
%b_addr.0 = phi i32 [ %b, %entry ], [ %tmp8, %bb ]
%a_addr.0 = phi i32 [ %a, %entry ], [ %tmp3, %bb ]
%tmp3 = xor i32 %a_addr.0, %b_addr.0
%tmp4not = xor i32 %tmp3, 2147483647
%tmp6 = and i32 %tmp4not, %b_addr.0
%tmp8 = shl i32 %tmp6, 1
%tmp10 = icmp eq i32 %tmp8, 0
br i1 %tmp10, label %bb12, label %bb
bb12:
ret i32 %tmp3
}
define i16 @sum16(i16 %a, i16 %b) nounwind {
entry:
br label %bb
bb:
%b_addr.0 = phi i16 [ %b, %entry ], [ %tmp8, %bb ]
%a_addr.0 = phi i16 [ %a, %entry ], [ %tmp3, %bb ]
%tmp3 = xor i16 %a_addr.0, %b_addr.0
%tmp4not = xor i16 %tmp3, 32767
%tmp6 = and i16 %tmp4not, %b_addr.0
%tmp8 = shl i16 %tmp6, 1
%tmp10 = icmp eq i16 %tmp8, 0
br i1 %tmp10, label %bb12, label %bb
bb12:
ret i16 %tmp3
}
define i8 @sum8(i8 %a, i8 %b) nounwind {
entry:
br label %bb
bb:
%b_addr.0 = phi i8 [ %b, %entry ], [ %tmp8, %bb ]
%a_addr.0 = phi i8 [ %a, %entry ], [ %tmp3, %bb ]
%tmp3 = xor i8 %a_addr.0, %b_addr.0
%tmp4not = xor i8 %tmp3, 127
%tmp6 = and i8 %tmp4not, %b_addr.0
%tmp8 = shl i8 %tmp6, 1
%tmp10 = icmp eq i8 %tmp8, 0
br i1 %tmp10, label %bb12, label %bb
bb12:
ret i8 %tmp3
}
define i32 @notransform(i32 %a, i32 %b) nounwind {
entry:
br label %bb
bb:
%b_addr.0 = phi i32 [ %b, %entry ], [ %tmp8, %bb ]
%a_addr.0 = phi i32 [ %a, %entry ], [ %tmp3, %bb ]
%tmp3 = xor i32 %a_addr.0, %b_addr.0
%tmp4not = xor i32 %tmp3, 2147483646
%tmp6 = and i32 %tmp4not, %b_addr.0
%tmp8 = shl i32 %tmp6, 1
%tmp10 = icmp eq i32 %tmp8, 0
br i1 %tmp10, label %bb12, label %bb
bb12:
ret i32 %tmp3
}