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[InstCombine] Fold ((C1 OP zext(X)) & C2) -> zext((C1 OP X) & C2) 

This further extends r292179 to support additional binary operators
beyond subtraction.

llvm-svn: 292238
This commit is contained in:
David Majnemer 2017-01-17 18:08:06 +00:00
parent e7d1f92344
commit de55c606d1
2 changed files with 74 additions and 15 deletions
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43
llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
View File

@ -1331,21 +1331,6 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
if (Value *V = FoldLogicalPlusAnd(Op0LHS, Op0RHS, AndRHS, true, I))
return BinaryOperator::CreateAnd(V, AndRHS);
// ((C1-zext(X)) & C2) -> zext((C1-X) & C2) if C2 fits in the bitwidth
// of X.
if (auto *ZI = dyn_cast<ZExtInst>(Op0RHS)) {
auto *X = ZI->getOperand(0);
ConstantInt *C1;
if (match(Op0LHS, m_ConstantInt(C1)) &&
AndRHSMask.isIntN(X->getType()->getScalarSizeInBits())) {
auto *TruncC1 = ConstantExpr::getTrunc(C1, X->getType());
auto *Sub = Builder->CreateSub(TruncC1, X);
auto *TruncC2 = ConstantExpr::getTrunc(AndRHS, X->getType());
auto *And = Builder->CreateAnd(Sub, TruncC2);
return new ZExtInst(And, I.getType());
}
}
// -x & 1 -> x & 1
if (AndRHSMask == 1 && match(Op0LHS, m_Zero()))
return BinaryOperator::CreateAnd(Op0RHS, AndRHS);
@ -1376,6 +1361,34 @@ Instruction *InstCombiner::visitAnd(BinaryOperator &I) {
break;
}
// ((C1 OP zext(X)) & C2) -> zext((C1-X) & C2) if C2 fits in the bitwidth
// of X and OP behaves well when given trunc(C1) and X.
switch (Op0I->getOpcode()) {
default:
break;
case Instruction::Xor:
case Instruction::Or:
case Instruction::Mul:
case Instruction::Add:
case Instruction::Sub:
Value *X;
ConstantInt *C1;
if (match(Op0I, m_BinOp(m_ZExt(m_Value(X)), m_ConstantInt(C1))) ||
match(Op0I, m_BinOp(m_ConstantInt(C1), m_ZExt(m_Value(X))))) {
if (AndRHSMask.isIntN(X->getType()->getScalarSizeInBits())) {
auto *TruncC1 = ConstantExpr::getTrunc(C1, X->getType());
Value *BinOp;
if (isa<ZExtInst>(Op0LHS))
BinOp = Builder->CreateBinOp(Op0I->getOpcode(), X, TruncC1);
else
BinOp = Builder->CreateBinOp(Op0I->getOpcode(), TruncC1, X);
auto *TruncC2 = ConstantExpr::getTrunc(AndRHS, X->getType());
auto *And = Builder->CreateAnd(BinOp, TruncC2);
return new ZExtInst(And, I.getType());
}
}
}
if (ConstantInt *Op0CI = dyn_cast<ConstantInt>(Op0I->getOperand(1)))
if (Instruction *Res = OptAndOp(Op0I, Op0CI, AndRHS, I))
return Res;

46
llvm/test/Transforms/InstCombine/and.ll
View File

@ -436,3 +436,49 @@ define i64 @test35(i32 %X) {
%res = and i64 %zsub, 240
ret i64 %res
}
define i64 @test36(i32 %X) {
; CHECK-LABEL: @test36(
; CHECK-NEXT: %[[sub:.*]] = add i32 %X, 7
; CHECK-NEXT: %[[and:.*]] = and i32 %[[sub]], 240
; CHECK-NEXT: %[[cst:.*]] = zext i32 %[[and]] to i64
; CHECK-NEXT: ret i64 %[[cst]]
%zext = zext i32 %X to i64
%zsub = add i64 %zext, 7
%res = and i64 %zsub, 240
ret i64 %res
}
define i64 @test37(i32 %X) {
; CHECK-LABEL: @test37(
; CHECK-NEXT: %[[sub:.*]] = mul i32 %X, 7
; CHECK-NEXT: %[[and:.*]] = and i32 %[[sub]], 240
; CHECK-NEXT: %[[cst:.*]] = zext i32 %[[and]] to i64
; CHECK-NEXT: ret i64 %[[cst]]
%zext = zext i32 %X to i64
%zsub = mul i64 %zext, 7
%res = and i64 %zsub, 240
ret i64 %res
}
define i64 @test38(i32 %X) {
; CHECK-LABEL: @test38(
; CHECK-NEXT: %[[and:.*]] = and i32 %X, 240
; CHECK-NEXT: %[[cst:.*]] = zext i32 %[[and]] to i64
; CHECK-NEXT: ret i64 %[[cst]]
%zext = zext i32 %X to i64
%zsub = xor i64 %zext, 7
%res = and i64 %zsub, 240
ret i64 %res
}
define i64 @test39(i32 %X) {
; CHECK-LABEL: @test39(
; CHECK-NEXT: %[[and:.*]] = and i32 %X, 240
; CHECK-NEXT: %[[cst:.*]] = zext i32 %[[and]] to i64
; CHECK-NEXT: ret i64 %[[cst]]
%zext = zext i32 %X to i64
%zsub = or i64 %zext, 7
%res = and i64 %zsub, 240
ret i64 %res
}