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[SelectionDAG] Add LegalTypes flag to getShiftAmountTy. Use it to unify and simplify DAGCombiner and simplifySetCC code and fix a bug. 

DAGCombiner and SimplifySetCC both use getPointerTy for shift amounts pre-legalization. DAGCombiner uses a single helper function to hide this. SimplifySetCC does it in multiple places.

This patch adds a defaulted parameter to getShiftAmountTy that can make it return getPointerTy for scalar types. Use this parameter to simplify the SimplifySetCC and DAGCombiner.

Additionally, there were two places in SimplifySetCC that were creating shifts using the target's preferred shift amount pre-legalization. If the target uses a narrow type and the type is illegal, this can cause SimplfiySetCC to create a shift with an amount that can't represent all possible shift values for the type. To fix this we should use pointer type there too.

Alternatively we could make getScalarShiftAmountTy for each target return a safe value for large types as proposed in D43445. And maybe we should still do that, but fixing the SimplifySetCC code keeps other targets from tripping over this in the future.

Fixes PR36250.

Differential Revision: https://reviews.llvm.org/D43449

llvm-svn: 325602
This commit is contained in:
Craig Topper 2018-02-20 17:41:05 +00:00
parent 010ae8dcbb
commit 35801fa5ce
5 changed files with 54 additions and 20 deletions
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3
llvm/include/llvm/CodeGen/TargetLowering.h
View File

@ -253,7 +253,8 @@ public:
/// A documentation for this function would be nice...
virtual MVT getScalarShiftAmountTy(const DataLayout &, EVT) const;
EVT getShiftAmountTy(EVT LHSTy, const DataLayout &DL) const;
EVT getShiftAmountTy(EVT LHSTy, const DataLayout &DL,
bool LegalTypes = true) const;
/// Returns the type to be used for the index operand of:
/// ISD::INSERT_VECTOR_ELT, ISD::EXTRACT_VECTOR_ELT,

6
llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
View File

@ -575,11 +575,7 @@ namespace {
/// legalization these can be huge.
EVT getShiftAmountTy(EVT LHSTy) {
assert(LHSTy.isInteger() && "Shift amount is not an integer type!");
if (LHSTy.isVector())
return LHSTy;
auto &DL = DAG.getDataLayout();
return LegalTypes ? TLI.getScalarShiftAmountTy(DL, LHSTy)
: TLI.getPointerTy(DL);
return TLI.getShiftAmountTy(LHSTy, DAG.getDataLayout(), LegalTypes);
}
/// This method returns true if we are running before type legalization or

21
llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp
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@ -2237,9 +2237,8 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
N0.getOpcode() == ISD::AND) {
auto &DL = DAG.getDataLayout();
if (auto *AndRHS = dyn_cast<ConstantSDNode>(N0.getOperand(1))) {
EVT ShiftTy = DCI.isBeforeLegalize()
? getPointerTy(DL)
: getShiftAmountTy(N0.getValueType(), DL);
EVT ShiftTy = getShiftAmountTy(N0.getValueType(), DL,
!DCI.isBeforeLegalize());
if (Cond == ISD::SETNE && C1 == 0) {// (X & 8) != 0 --> (X & 8) >> 3
// Perform the xform if the AND RHS is a single bit.
if (AndRHS->getAPIntValue().isPowerOf2()) {
@ -2271,9 +2270,8 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
if ((-AndRHSC).isPowerOf2() && (AndRHSC & C1) == C1) {
unsigned ShiftBits = AndRHSC.countTrailingZeros();
auto &DL = DAG.getDataLayout();
EVT ShiftTy = DCI.isBeforeLegalize()
? getPointerTy(DL)
: getShiftAmountTy(N0.getValueType(), DL);
EVT ShiftTy = getShiftAmountTy(N0.getValueType(), DL,
!DCI.isBeforeLegalize());
EVT CmpTy = N0.getValueType();
SDValue Shift = DAG.getNode(ISD::SRL, dl, CmpTy, N0.getOperand(0),
DAG.getConstant(ShiftBits, dl,
@ -2303,9 +2301,8 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
if (ShiftBits && NewC.getMinSignedBits() <= 64 &&
isLegalICmpImmediate(NewC.getSExtValue())) {
auto &DL = DAG.getDataLayout();
EVT ShiftTy = DCI.isBeforeLegalize()
? getPointerTy(DL)
: getShiftAmountTy(N0.getValueType(), DL);
EVT ShiftTy = getShiftAmountTy(N0.getValueType(), DL,
!DCI.isBeforeLegalize());
EVT CmpTy = N0.getValueType();
SDValue Shift = DAG.getNode(ISD::SRL, dl, CmpTy, N0,
DAG.getConstant(ShiftBits, dl, ShiftTy));
@ -2499,7 +2496,8 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
SDValue SH = DAG.getNode(
ISD::SHL, dl, N1.getValueType(), N1,
DAG.getConstant(1, dl,
getShiftAmountTy(N1.getValueType(), DL)));
getShiftAmountTy(N1.getValueType(), DL,
!DCI.isBeforeLegalize())));
if (!DCI.isCalledByLegalizer())
DCI.AddToWorklist(SH.getNode());
return DAG.getSetCC(dl, VT, N0.getOperand(0), SH, Cond);
@ -2524,7 +2522,8 @@ SDValue TargetLowering::SimplifySetCC(EVT VT, SDValue N0, SDValue N1,
// X == (Z-X) --> X<<1 == Z
SDValue SH = DAG.getNode(
ISD::SHL, dl, N1.getValueType(), N0,
DAG.getConstant(1, dl, getShiftAmountTy(N0.getValueType(), DL)));
DAG.getConstant(1, dl, getShiftAmountTy(N0.getValueType(), DL,
!DCI.isBeforeLegalize())));
if (!DCI.isCalledByLegalizer())
DCI.AddToWorklist(SH.getNode());
return DAG.getSetCC(dl, VT, SH, N1.getOperand(0), Cond);

7
llvm/lib/CodeGen/TargetLoweringBase.cpp
View File

@ -685,12 +685,13 @@ MVT TargetLoweringBase::getScalarShiftAmountTy(const DataLayout &DL,
return MVT::getIntegerVT(8 * DL.getPointerSize(0));
}
EVT TargetLoweringBase::getShiftAmountTy(EVT LHSTy,
const DataLayout &DL) const {
EVT TargetLoweringBase::getShiftAmountTy(EVT LHSTy, const DataLayout &DL,
bool LegalTypes) const {
assert(LHSTy.isInteger() && "Shift amount is not an integer type!");
if (LHSTy.isVector())
return LHSTy;
return getScalarShiftAmountTy(DL, LHSTy);
return LegalTypes ? getScalarShiftAmountTy(DL, LHSTy)
: getPointerTy(DL);
}
bool TargetLoweringBase::canOpTrap(unsigned Op, EVT VT) const {

37
llvm/test/CodeGen/X86/legalize-shift.ll Normal file
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@ -0,0 +1,37 @@
; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
; RUN: llc < %s -mtriple=i686-unknown-unknown | FileCheck %s --check-prefix=X86
; RUN: llc < %s -mtriple=x86_64-unknown-unknown | FileCheck %s --check-prefix=X64
define void @PR36250() {
; X86-LABEL: PR36250:
; X86: # %bb.0:
; X86-NEXT: movl (%eax), %eax
; X86-NEXT: movl %eax, %ecx
; X86-NEXT: roll %ecx
; X86-NEXT: addl %eax, %eax
; X86-NEXT: movl %ecx, %edx
; X86-NEXT: orl %edx, %edx
; X86-NEXT: orl %ecx, %edx
; X86-NEXT: orl %eax, %edx
; X86-NEXT: orl %ecx, %edx
; X86-NEXT: sete (%eax)
; X86-NEXT: retl
;
; X64-LABEL: PR36250:
; X64: # %bb.0:
; X64-NEXT: movq (%rax), %rax
; X64-NEXT: movq %rax, %rcx
; X64-NEXT: rolq %rcx
; X64-NEXT: addq %rax, %rax
; X64-NEXT: movq %rcx, %rdx
; X64-NEXT: orq %rdx, %rdx
; X64-NEXT: orq %rax, %rdx
; X64-NEXT: orq %rcx, %rdx
; X64-NEXT: sete (%rax)
; X64-NEXT: retq
%1 = load i448, i448* undef
%2 = sub i448 0, %1
%3 = icmp eq i448 %1, %2
store i1 %3, i1* undef
ret void
}