maxjhandsome
/
llvm-project
forked from OSchip/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Releases Wiki Activity

[InstCombine] use m_APInt to allow ashr folds for vectors with splat constants 

We may be able to assert that no shl-shl or lshr-lshr pairs ever get here
because we should have already handled those in foldShiftedShift().

llvm-svn: 292726
This commit is contained in:
Sanjay Patel 2017-01-21 17:59:59 +00:00
parent 24c6f88e4c
commit 478a83c905
2 changed files with 30 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
llvm/lib/Transforms/InstCombine/InstCombineShifts.cpp
View File

@ -315,14 +315,32 @@ static Instruction *
foldShiftByConstOfShiftByConst(BinaryOperator &I, const APInt *COp1,
InstCombiner::BuilderTy *Builder) {
Value *Op0 = I.getOperand(0);
uint32_t TypeBits = Op0->getType()->getScalarSizeInBits();
unsigned TypeBits = Op0->getType()->getScalarSizeInBits();
// Find out if this is a shift of a shift by a constant.
BinaryOperator *ShiftOp = dyn_cast<BinaryOperator>(Op0);
if (!ShiftOp || !ShiftOp->isShift() ||
!isa<ConstantInt>(ShiftOp->getOperand(1)))
if (!ShiftOp || !ShiftOp->isShift())
return nullptr;
const APInt *ShAmt1;
if (!match(ShiftOp->getOperand(1), m_APInt(ShAmt1)))
return nullptr;
// Check for (X << c1) << c2 and (X >> c1) >> c2
if (I.getOpcode() == ShiftOp->getOpcode()) {
unsigned AmtSum = (*ShAmt1 + *COp1).getZExtValue();
// If this is an oversized composite shift, then unsigned shifts become
// zero (handled in InstSimplify) and ashr saturates.
if (AmtSum >= TypeBits) {
if (I.getOpcode() != Instruction::AShr)
return nullptr;
AmtSum = TypeBits - 1; // Saturate to 31 for i32 ashr.
}
return BinaryOperator::Create(I.getOpcode(), ShiftOp->getOperand(0),
ConstantInt::get(I.getType(), AmtSum));
}
// This is a constant shift of a constant shift. Be careful about hiding
// shl instructions behind bit masks. They are used to represent multiplies
// by a constant, and it is important that simple arithmetic expressions
@ -335,31 +353,20 @@ foldShiftByConstOfShiftByConst(BinaryOperator &I, const APInt *COp1,
// Combinations of right and left shifts will still be optimized in
// DAGCombine where scalar evolution no longer applies.
ConstantInt *ShiftAmt1C = cast<ConstantInt>(ShiftOp->getOperand(1));
// FIXME: Everything under here should be extended to work with vector types.
auto *ShiftAmt1C = dyn_cast<ConstantInt>(ShiftOp->getOperand(1));
if (!ShiftAmt1C)
return nullptr;
uint32_t ShiftAmt1 = ShiftAmt1C->getLimitedValue(TypeBits);
uint32_t ShiftAmt2 = COp1->getLimitedValue(TypeBits);
assert(ShiftAmt2 != 0 && "Should have been simplified earlier");
if (ShiftAmt1 == 0)
return nullptr; // Will be simplified in the future.
Value *X = ShiftOp->getOperand(0);
IntegerType *Ty = cast<IntegerType>(I.getType());
// Check for (X << c1) << c2 and (X >> c1) >> c2
if (I.getOpcode() == ShiftOp->getOpcode()) {
uint32_t AmtSum = ShiftAmt1 + ShiftAmt2; // Fold into one big shift.
// If this is an oversized composite shift, then unsigned shifts become
// zero (handled in InstSimplify) and ashr saturates.
if (AmtSum >= TypeBits) {
if (I.getOpcode() != Instruction::AShr)
return nullptr;
AmtSum = TypeBits - 1; // Saturate to 31 for i32 ashr.
}
return BinaryOperator::Create(I.getOpcode(), X,
ConstantInt::get(Ty, AmtSum));
}
if (ShiftAmt1 == ShiftAmt2) {
// If we have ((X << C) >>u C), turn this into X & (-1 >>u C).
if (I.getOpcode() == Instruction::LShr &&

8
llvm/test/Transforms/InstCombine/shift-sra.ll
View File

@ -139,13 +139,11 @@ define i32 @ashr_overshift(i32 %x) {
ret i32 %sh2
}
; FIXME:
; (X >>s C1) >>s C2 --> X >>s (C1 + C2)
define <2 x i32> @ashr_ashr_splat_vec(<2 x i32> %x) {
; CHECK-LABEL: @ashr_ashr_splat_vec(
; CHECK-NEXT: [[SH1:%.*]] = ashr <2 x i32> %x, <i32 5, i32 5>
; CHECK-NEXT: [[SH2:%.*]] = ashr <2 x i32> [[SH1]], <i32 7, i32 7>
; CHECK-NEXT: [[SH2:%.*]] = ashr <2 x i32> %x, <i32 12, i32 12>
; CHECK-NEXT: ret <2 x i32> [[SH2]]
;
%sh1 = ashr <2 x i32> %x, <i32 5, i32 5>
@ -153,13 +151,11 @@ define <2 x i32> @ashr_ashr_splat_vec(<2 x i32> %x) {
ret <2 x i32> %sh2
}
; FIXME:
; (X >>s C1) >>s C2 --> X >>s (Bitwidth - 1)
define <2 x i32> @ashr_overshift_splat_vec(<2 x i32> %x) {
; CHECK-LABEL: @ashr_overshift_splat_vec(
; CHECK-NEXT: [[SH1:%.*]] = ashr <2 x i32> %x, <i32 15, i32 15>
; CHECK-NEXT: [[SH2:%.*]] = ashr <2 x i32> [[SH1]], <i32 17, i32 17>
; CHECK-NEXT: [[SH2:%.*]] = ashr <2 x i32> %x, <i32 31, i32 31>
; CHECK-NEXT: ret <2 x i32> [[SH2]]
;
%sh1 = ashr <2 x i32> %x, <i32 15, i32 15>