6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-02-06 06:33:24 +00:00
Code Issues Projects Releases Wiki Activity

PR19753: Optimize comparisons with "ashr exact" of a constanst.

Browse Source 
Patch by suyog sarda.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209903 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2014-05-30 15:54:32 +00:00
parent 6319c0c520
commit fcb9926813
2 changed files with 25 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -2439,6 +2439,23 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
return new ICmpInst(I.getPredicate(), A, B); return new ICmpInst(I.getPredicate(), A, B);
} }
// PR19753:
// (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.
{
ConstantInt *CI2;
if (match(Op0, m_AShr(m_ConstantInt(CI2), m_Value(A))) &&
(cast<BinaryOperator>(Op0)->isExact())) {
APInt Quotient = CI2->getValue().sdiv(CI->getValue());
unsigned shift = Quotient.logBase2();
return new ICmpInst(I.getPredicate(), A,
ConstantInt::get(A->getType(), shift));
}
}
// If we have an icmp le or icmp ge instruction, turn it into the // If we have an icmp le or icmp ge instruction, turn it into the
// appropriate icmp lt or icmp gt instruction. This allows us to rely on // appropriate icmp lt or icmp gt instruction. This allows us to rely on
// them being folded in the code below. The SimplifyICmpInst code has // them being folded in the code below. The SimplifyICmpInst code has

8
test/Transforms/InstCombine/icmp.ll
View File

@ -1365,3 +1365,11 @@ define i1 @icmp_neg_cst_slt(i32 %a) {
%2 = icmp slt i32 %1, -10 %2 = icmp slt i32 %1, -10
ret i1 %2 ret i1 %2
} }
; CHECK-LABEL: @exact_ashr_eq_false
; CHECK-NEXT: icmp eq i32 %a, 1
define i1 @exact_ashr_eq_false(i32 %a) {
%shr = ashr exact i32 -30, %a
%cmp = icmp eq i32 %shr, -15
ret i1 %cmp
}