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Revert 209903 and 210040.

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The messages were

 "PR19753: Optimize comparisons with "ashr exact" of a constanst."
 "Added support to optimize comparisons with "lshr exact" of a constant."

They were not correctly handling signed/unsigned operation differences,
causing pr19958.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210393 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Rafael Espindola 2014-06-07 04:12:35 +00:00
parent 808823cf77
commit 68caf1727f
2 changed files with 0 additions and 56 deletions
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40
lib/Transforms/InstCombine/InstCombineCompares.cpp
View File

@ -2318,32 +2318,6 @@ 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);
@ -2465,20 +2439,6 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
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. Similar for lshr.
{
APInt Quotient;
if (checkShrExact(Op0, Quotient, CI, A)) {
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
// appropriate icmp lt or icmp gt instruction. This allows us to rely on
// them being folded in the code below. The SimplifyICmpInst code has

16
test/Transforms/InstCombine/icmp.ll
View File

@ -1382,19 +1382,3 @@ define i1 @icmp_neg_cst_slt(i32 %a) {
%2 = icmp slt i32 %1, -10
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
}
; 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
}