We used to combine "sext(setcc x, y, cc) -> (select (setcc x, y, cc), -1, 0)"
Instead, we should combine to (select (setcc x, y, cc), T, 0) where the value
of T is 1 or -1, depending on the type of the setcc, and getBooleanContents()
for the type if it is not i1.
This fixes PR28504.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277371
91177308-0d34-0410-b5e6-
96231b3b80d8
/// from getBooleanContents().
bool isConstFalseVal(const SDNode *N) const;
+ /// Return a constant of type VT that contains a true value that respects
+ /// getBooleanContents()
+ SDValue getConstTrueVal(SelectionDAG &DAG, EVT VT, const SDLoc &DL) const;
+
/// Return if \p N is a True value when extended to \p VT.
bool isExtendedTrueVal(const ConstantSDNode *N, EVT VT, bool Signed) const;
}
}
- // sext(setcc x, y, cc) -> (select (setcc x, y, cc), -1, 0)
- unsigned ElementWidth = VT.getScalarType().getSizeInBits();
+ // sext(setcc x, y, cc) -> (select (setcc x, y, cc), T, 0)
+ // Here, T can be 1 or -1, depending on the type of the setcc and
+ // getBooleanContents().
+ unsigned SetCCWidth = N0.getValueType().getScalarSizeInBits();
+
SDLoc DL(N);
- SDValue NegOne =
- DAG.getConstant(APInt::getAllOnesValue(ElementWidth), DL, VT);
+ // To determine the "true" side of the select, we need to know the high bit
+ // of the value returned by the setcc if it evaluates to true.
+ // If the type of the setcc is i1, then the true case of the select is just
+ // sext(i1 1), that is, -1.
+ // If the type of the setcc is larger (say, i8) then the value of the high
+ // bit depends on getBooleanContents(). So, ask TLI for a real "true" value
+ // of the appropriate width.
+ SDValue ExtTrueVal =
+ (SetCCWidth == 1)
+ ? DAG.getConstant(APInt::getAllOnesValue(VT.getScalarSizeInBits()),
+ DL, VT)
+ : TLI.getConstTrueVal(DAG, VT, DL);
+
if (SDValue SCC = SimplifySelectCC(
- DL, N0.getOperand(0), N0.getOperand(1), NegOne,
+ DL, N0.getOperand(0), N0.getOperand(1), ExtTrueVal,
DAG.getConstant(0, DL, VT),
cast<CondCodeSDNode>(N0.getOperand(2))->get(), true))
return SCC;
TLI.isOperationLegal(ISD::SETCC, N0.getOperand(0).getValueType())) {
SDLoc DL(N);
ISD::CondCode CC = cast<CondCodeSDNode>(N0.getOperand(2))->get();
- SDValue SetCC = DAG.getSetCC(DL, SetCCVT,
- N0.getOperand(0), N0.getOperand(1), CC);
- return DAG.getSelect(DL, VT, SetCC,
- NegOne, DAG.getConstant(0, DL, VT));
+ SDValue SetCC =
+ DAG.getSetCC(DL, SetCCVT, N0.getOperand(0), N0.getOperand(1), CC);
+ return DAG.getSelect(DL, VT, SetCC, ExtTrueVal,
+ DAG.getConstant(0, DL, VT));
}
}
}
llvm_unreachable("Invalid boolean contents");
}
+SDValue TargetLowering::getConstTrueVal(SelectionDAG &DAG, EVT VT,
+ const SDLoc &DL) const {
+ unsigned ElementWidth = VT.getScalarSizeInBits();
+ APInt TrueInt =
+ getBooleanContents(VT) == TargetLowering::ZeroOrOneBooleanContent
+ ? APInt(ElementWidth, 1)
+ : APInt::getAllOnesValue(ElementWidth);
+ return DAG.getConstant(TrueInt, DL, VT);
+}
+
bool TargetLowering::isConstFalseVal(const SDNode *N) const {
if (!N)
return false;
--- /dev/null
+; RUN: llc -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+
+; The test case is rather involved, because we need to get to a state where
+; We have a sext(setcc x, y, cc) -> (select (setcc x, y, cc), T, 0) combine,
+; BUT this combine is only triggered post-legalization, so the setcc's return
+; type is i8. So we can't have the combine opportunity be exposed too early.
+; Basically, what we want to see is that the compare result zero-extended, and
+; then stored. Only one zext, and no sexts.
+
+; CHECK-LABEL: main:
+; CHECK: movzbl (%rdi), %[[EAX:.*]]
+; CHECK-NEXT: xorl %e[[C:.]]x, %e[[C]]x
+; CHECK-NEXT: cmpl $1, %[[EAX]]
+; CHECK-NEXT: sete %[[C]]l
+; CHECK-NEXT: movl %e[[C]]x, (%rsi)
+define void @main(i8* %p, i32* %q) {
+bb:
+ %tmp4 = load i8, i8* %p, align 1
+ %tmp5 = sext i8 %tmp4 to i32
+ %tmp6 = load i8, i8* %p, align 1
+ %tmp7 = zext i8 %tmp6 to i32
+ %tmp8 = sub nsw i32 %tmp5, %tmp7
+ %tmp11 = icmp eq i32 %tmp7, 1
+ %tmp12 = zext i1 %tmp11 to i32
+ %tmp13 = add nsw i32 %tmp8, %tmp12
+ %tmp14 = trunc i32 %tmp13 to i8
+ %tmp15 = sext i8 %tmp14 to i16
+ %tmp16 = sext i16 %tmp15 to i32
+ store i32 %tmp16, i32* %q, align 4
+ br i1 %tmp11, label %bb21, label %bb22
+
+bb21: ; preds = %bb
+ unreachable
+
+bb22: ; preds = %bb
+ ret void
+}