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[IRCE] Remove folding of two range checks into RANGE_CHECK_BOTH 

The logic of replacing of a couple `RANGE_CHECK_LOWER + RANGE_CHECK_UPPER`
into `RANGE_CHECK_BOTH` in fact duplicates the logic of range intersection which
happens when we calculate safe iteration space. Effectively, the result of intersection of
these ranges doesn't differ from the range of merged range check.

We chose to remove duplicating logic in favor of code simplicity.

Differential Revision: https://reviews.llvm.org/D39589

llvm-svn: 318508
This commit is contained in:
Max Kazantsev 2017-11-17 06:49:26 +00:00
parent b5b0c02249
commit 1ac6e8ae61
2 changed files with 20 additions and 34 deletions
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31
llvm/lib/Transforms/Scalar/InductiveRangeCheckElimination.cpp
View File

@ -367,37 +367,12 @@ void InductiveRangeCheck::extractRangeChecksFromCond(
if (!Visited.insert(Condition).second) if (!Visited.insert(Condition).second)
return; return;
// TODO: Do the same for OR, XOR, NOT etc?
if (match(Condition, m_And(m_Value(), m_Value()))) { if (match(Condition, m_And(m_Value(), m_Value()))) {
SmallVector<InductiveRangeCheck, 8> SubChecks;
extractRangeChecksFromCond(L, SE, cast<User>(Condition)->getOperandUse(0), extractRangeChecksFromCond(L, SE, cast<User>(Condition)->getOperandUse(0),
SubChecks, Visited); Checks, Visited);
extractRangeChecksFromCond(L, SE, cast<User>(Condition)->getOperandUse(1), extractRangeChecksFromCond(L, SE, cast<User>(Condition)->getOperandUse(1),
SubChecks, Visited); Checks, Visited);
if (SubChecks.size() == 2) {
// Handle a special case where we know how to merge two checks separately
// checking the upper and lower bounds into a full range check.
const auto &RChkA = SubChecks[0];
const auto &RChkB = SubChecks[1];
if ((RChkA.End == RChkB.End || !RChkA.End || !RChkB.End) &&
RChkA.Begin == RChkB.Begin && RChkA.Step == RChkB.Step &&
RChkA.IsSigned == RChkB.IsSigned) {
// If RChkA.Kind == RChkB.Kind then we just found two identical checks.
// But if one of them is a RANGE_CHECK_LOWER and the other is a
// RANGE_CHECK_UPPER (only possibility if they're different) then
// together they form a RANGE_CHECK_BOTH.
SubChecks[0].Kind =
(InductiveRangeCheck::RangeCheckKind)(RChkA.Kind | RChkB.Kind);
SubChecks[0].End = RChkA.End ? RChkA.End : RChkB.End;
SubChecks[0].CheckUse = &ConditionUse;
SubChecks[0].IsSigned = RChkA.IsSigned;
// We updated one of the checks in place, now erase the other.
SubChecks.pop_back();
}
}
Checks.insert(Checks.end(), SubChecks.begin(), SubChecks.end());
return; return;
} }

23
llvm/test/Transforms/IRCE/single-access-with-preloop.ll
View File

@ -40,13 +40,24 @@ define void @single_access_with_preloop(i32 *%arr, i32 *%a_len_ptr, i32 %n, i32
; CHECK: [[not_safe_start_2:[^ ]+]] = add i32 %offset, -1 ; CHECK: [[not_safe_start_2:[^ ]+]] = add i32 %offset, -1
; CHECK: [[not_safe_end:[^ ]+]] = sub i32 [[not_safe_start_2]], %len ; CHECK: [[not_safe_upper_end:[^ ]+]] = sub i32 [[not_safe_start_2]], %len
; CHECK: [[not_exit_mainloop_at_cond_loclamp:[^ ]+]] = icmp sgt i32 [[not_safe_end]], [[not_n]] ; CHECK: [[not_exit_mainloop_at_cond_loclamp:[^ ]+]] = icmp sgt i32 [[not_safe_upper_end]], [[not_n]]
; CHECK: [[not_exit_mainloop_at_loclamp:[^ ]+]] = select i1 [[not_exit_mainloop_at_cond_loclamp]], i32 [[not_safe_end]], i32 [[not_n]] ; CHECK: [[not_exit_mainloop_at_loclamp:[^ ]+]] = select i1 [[not_exit_mainloop_at_cond_loclamp]], i32 [[not_safe_upper_end]], i32 [[not_n]]
; CHECK: [[exit_mainloop_at_loclamp:[^ ]+]] = sub i32 -1, [[not_exit_mainloop_at_loclamp]] ; CHECK: [[not_safe_lower_end:[^ ]+]] = add i32 %offset, -2147483648
; CHECK: [[exit_mainloop_at_cmp:[^ ]+]] = icmp sgt i32 [[exit_mainloop_at_loclamp]], 0 ; CHECK: [[not_exit_mainloop_at_cond_hiclamp:[^ ]+]] = icmp sgt i32 [[not_exit_mainloop_at_loclamp]], [[not_safe_lower_end]]
; CHECK: [[exit_mainloop_at:[^ ]+]] = select i1 [[exit_mainloop_at_cmp]], i32 [[exit_mainloop_at_loclamp]], i32 0 ; CHECK: [[not_exit_mainloop_at_hiclamp:[^ ]+]] = select i1 [[not_exit_mainloop_at_cond_hiclamp]], i32 [[not_exit_mainloop_at_loclamp]], i32 [[not_safe_lower_end]]
; CHECK: [[exit_mainloop_at_hiclamp:[^ ]+]] = sub i32 -1, [[not_exit_mainloop_at_hiclamp]]
; CHECK: [[exit_mainloop_at_cmp:[^ ]+]] = icmp sgt i32 [[exit_mainloop_at_hiclamp]], 0
; CHECK: [[exit_mainloop_at:[^ ]+]] = select i1 [[exit_mainloop_at_cmp]], i32 [[exit_mainloop_at_hiclamp]], i32 0
; CHECK: mainloop:
; CHECK: br label %loop
; CHECK: loop:
; CHECK: %abc.high = icmp slt i32 %array.idx, %len
; CHECK: %abc.low = icmp sge i32 %array.idx, 0
; CHECK: %abc = and i1 true, true
; CHECK: br i1 %abc, label %in.bounds, label %out.of.bounds.loopexit8
; CHECK: in.bounds: ; CHECK: in.bounds:
; CHECK: [[continue_mainloop_cond:[^ ]+]] = icmp slt i32 %idx.next, [[exit_mainloop_at]] ; CHECK: [[continue_mainloop_cond:[^ ]+]] = icmp slt i32 %idx.next, [[exit_mainloop_at]]