mirror of
https://github.com/c64scene-ar/llvm-6502.git
synced 2024-08-26 07:29:55 +00:00
Added support to optimize comparisons with "lshr exact" of a constant.
Patch by Rahul Jain. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210040 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
parent
f50e395308
commit
83223f52e7
@ -2318,6 +2318,32 @@ static bool swapMayExposeCSEOpportunities(const Value * Op0,
|
||||
return GlobalSwapBenefits > 0;
|
||||
}
|
||||
|
||||
// Helper function to check whether Op represents a lshr/ashr exact
|
||||
// instruction. For example:
|
||||
// (icmp (ashr exact const2, A), const1) -> icmp A, Log2(const2/const1)
|
||||
// Here if Op represents -> (ashr exact const2, A), and CI represents
|
||||
// const1, we compute Quotient as const2/const1.
|
||||
|
||||
static bool checkShrExact(Value *Op, APInt &Quotient, const ConstantInt *CI,
|
||||
Value *&A) {
|
||||
|
||||
ConstantInt *CI2;
|
||||
if (match(Op, m_AShr(m_ConstantInt(CI2), m_Value(A))) &&
|
||||
(cast<BinaryOperator>(Op)->isExact())) {
|
||||
Quotient = CI2->getValue().sdiv(CI->getValue());
|
||||
return true;
|
||||
}
|
||||
|
||||
// Handle the case for lhsr.
|
||||
if (match(Op, m_LShr(m_ConstantInt(CI2), m_Value(A))) &&
|
||||
(cast<BinaryOperator>(Op)->isExact())) {
|
||||
Quotient = CI2->getValue().udiv(CI->getValue());
|
||||
return true;
|
||||
}
|
||||
|
||||
return false;
|
||||
}
|
||||
|
||||
Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
|
||||
bool Changed = false;
|
||||
Value *Op0 = I.getOperand(0), *Op1 = I.getOperand(1);
|
||||
@ -2443,13 +2469,10 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
|
||||
// (icmp (ashr exact const2, A), const1) -> icmp A, Log2(const2/const1)
|
||||
// Cases where const1 doesn't divide const2 exactly or Quotient is not
|
||||
// exact of log2 are handled by SimplifyICmpInst call above where we
|
||||
// return false.
|
||||
// TODO: Handle this for lshr exact with udiv.
|
||||
// return false. Similar for lshr.
|
||||
{
|
||||
ConstantInt *CI2;
|
||||
if (match(Op0, m_AShr(m_ConstantInt(CI2), m_Value(A))) &&
|
||||
(cast<BinaryOperator>(Op0)->isExact())) {
|
||||
APInt Quotient = CI2->getValue().sdiv(CI->getValue());
|
||||
APInt Quotient;
|
||||
if (checkShrExact(Op0, Quotient, CI, A)) {
|
||||
unsigned shift = Quotient.logBase2();
|
||||
return new ICmpInst(I.getPredicate(), A,
|
||||
ConstantInt::get(A->getType(), shift));
|
||||
|
@ -1390,3 +1390,11 @@ define i1 @exact_ashr_eq_false(i32 %a) {
|
||||
%cmp = icmp eq i32 %shr, -15
|
||||
ret i1 %cmp
|
||||
}
|
||||
|
||||
; CHECK-LABEL: @exact_lhsr
|
||||
; CHECK-NEXT: icmp eq i32 %a, 3
|
||||
define i1 @exact_lhsr(i32 %a) {
|
||||
%shr = lshr exact i32 80, %a
|
||||
%cmp = icmp eq i32 %shr, 10
|
||||
ret i1 %cmp
|
||||
}
|
||||
|
Loading…
Reference in New Issue
Block a user