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[FastISel][AArch64] Teach the address computation to also fold sub instructions.

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Tiny enhancement to the address computation code to also fold sub instructions
if the rhs is constant and can be folded into the offset.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219186 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Juergen Ributzka
2014-10-07 03:40:03 +00:00
parent ca07e256f6
commit 3692081566
2 changed files with 22 additions and 11 deletions
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13
lib/Target/AArch64/AArch64FastISel.cpp
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@@ -590,7 +590,7 @@ bool AArch64FastISel::computeAddress(const Value *Obj, Address &Addr, Type *Ty)
std::swap(LHS, RHS);
if (const ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
Addr.setOffset(Addr.getOffset() + (uint64_t)CI->getSExtValue());
Addr.setOffset(Addr.getOffset() + CI->getSExtValue());
return computeAddress(LHS, Addr, Ty);
}
@@ -601,6 +601,17 @@ bool AArch64FastISel::computeAddress(const Value *Obj, Address &Addr, Type *Ty)
break;
}
case Instruction::Sub: {
// Subs of constants are common and easy enough.
const Value *LHS = U->getOperand(0);
const Value *RHS = U->getOperand(1);
if (const ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) {
Addr.setOffset(Addr.getOffset() - CI->getSExtValue());
return computeAddress(LHS, Addr, Ty);
}
break;
}
case Instruction::Shl: {
if (Addr.getOffsetReg())
break;