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[IRSim] Ensure that assignment accurately reduces potential mapping between different candidates

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Previous:
When we do not make decisions about commutative operands, we can end up in a situation where two values have two potential canonical numbers between two regions. This ensures that an ordering is decided after the initial structure between two regions is determined.

Current:
Previously the outliner only checked that assignment to a value matched what was already known, this patch makes sure that it matches what has already been found, and creates a mapping between the two values where it is a one-to-one mapping.

Reviewer: paquette
Differential Revision: https://reviews.llvm.org/D139336
This commit is contained in:
Andrew Litteken 2022-12-12 23:51:11 -06:00
parent 21cd04c46f
commit 47f528217e
3 changed files with 140 additions and 10 deletions
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18
llvm/include/llvm/Analysis/IRSimilarityIdentifier.h
View File

@ -768,6 +768,24 @@ public:
static bool compareCommutativeOperandMapping(OperandMapping A,
OperandMapping B);
/// Compare the GVN of the assignment value in corresponding instructions in
/// IRSimilarityCandidates \p A and \p B and check that there exists a mapping
/// between the values and replaces the mapping with a one-to-one value if
/// needed.
///
/// \param InstValA - The assignment GVN from the first IRSimilarityCandidate.
/// \param InstValB - The assignment GVN from the second
/// IRSimilarityCandidate.
/// \param [in,out] ValueNumberMappingA - A mapping of value numbers from
/// candidate \p A to candidate \B.
/// \param [in,out] ValueNumberMappingB - A mapping of value numbers from
/// candidate \p B to candidate \A.
/// \returns true if the IRSimilarityCandidates assignments are compatible.
static bool compareAssignmentMapping(
const unsigned InstValA, const unsigned &InstValB,
DenseMap<unsigned, DenseSet<unsigned>> &ValueNumberMappingA,
DenseMap<unsigned, DenseSet<unsigned>> &ValueNumberMappingB);
/// Compare the relative locations in \p A and \p B and check that the
/// distances match if both locations are contained in the region, and that
/// the branches both point outside the region if they do not.

43
llvm/lib/Analysis/IRSimilarityIdentifier.cpp
View File

@ -718,6 +718,34 @@ bool IRSimilarityCandidate::compareCommutativeOperandMapping(
return true;
}
bool IRSimilarityCandidate::compareAssignmentMapping(
const unsigned InstValA, const unsigned &InstValB,
DenseMap<unsigned, DenseSet<unsigned>> &ValueNumberMappingA,
DenseMap<unsigned, DenseSet<unsigned>> &ValueNumberMappingB) {
DenseMap<unsigned, DenseSet<unsigned>>::iterator ValueMappingIt;
bool WasInserted;
std::tie(ValueMappingIt, WasInserted) = ValueNumberMappingA.insert(
std::make_pair(InstValA, DenseSet<unsigned>({InstValB})));
if (!WasInserted && !ValueMappingIt->second.contains(InstValB))
return false;
else if (ValueMappingIt->second.size() != 1) {
for (unsigned OtherVal : ValueMappingIt->second) {
if (OtherVal == InstValB)
continue;
if (ValueNumberMappingA.find(OtherVal) == ValueNumberMappingA.end())
continue;
if (!ValueNumberMappingA[OtherVal].contains(InstValA))
continue;
ValueNumberMappingA[OtherVal].erase(InstValA);
}
ValueNumberMappingA.erase(ValueMappingIt);
std::tie(ValueMappingIt, WasInserted) = ValueNumberMappingA.insert(
std::make_pair(InstValA, DenseSet<unsigned>({InstValB})));
}
return true;
}
bool IRSimilarityCandidate::checkRelativeLocations(RelativeLocMapping A,
RelativeLocMapping B) {
// Get the basic blocks the label refers to.
@ -775,8 +803,6 @@ bool IRSimilarityCandidate::compareStructure(
// in one candidate to values in the other candidate. If we create a set with
// one element, and that same element maps to the original element in the
// candidate we have a good mapping.
DenseMap<unsigned, DenseSet<unsigned>>::iterator ValueMappingIt;
// Iterate over the instructions contained in each candidate
unsigned SectionLength = A.getStartIdx() + A.getLength();
@ -799,16 +825,13 @@ bool IRSimilarityCandidate::compareStructure(
unsigned InstValA = A.ValueToNumber.find(IA)->second;
unsigned InstValB = B.ValueToNumber.find(IB)->second;
bool WasInserted;
// Ensure that the mappings for the instructions exists.
std::tie(ValueMappingIt, WasInserted) = ValueNumberMappingA.insert(
std::make_pair(InstValA, DenseSet<unsigned>({InstValB})));
if (!WasInserted && !ValueMappingIt->second.contains(InstValB))
if (!compareAssignmentMapping(InstValA, InstValB, ValueNumberMappingA,
ValueNumberMappingB))
return false;
std::tie(ValueMappingIt, WasInserted) = ValueNumberMappingB.insert(
std::make_pair(InstValB, DenseSet<unsigned>({InstValA})));
if (!WasInserted && !ValueMappingIt->second.contains(InstValA))
if (!compareAssignmentMapping(InstValB, InstValA, ValueNumberMappingB,
ValueNumberMappingA))
return false;
// We have different paths for commutative instructions and non-commutative

89
llvm/test/Transforms/IROutliner/outlining-larger-size-commutative.ll Normal file
View File

@ -0,0 +1,89 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -p iroutliner,verify -ir-outlining-no-cost < %s | FileCheck %s
; This test checks that commutative instructions where the operands are
; swapped are outlined as the same function.
; It also checks that non-commutative instructions outlined as different
; functions when the operands are swapped;
; These are identical functions, except that in the flipped functions,
; the operands in the adds are commuted. However, since add instructions
; are commutative, we should still outline from all four as the same
; instruction.
define void @function1(i32 %a, i32 %b) {
; CHECK-LABEL: @function1(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[BLOCK_1:%.*]]
; CHECK: block_0:
; CHECK-NEXT: [[TMP0:%.*]] = add i32 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = add i32 [[TMP4:%.*]], 1
; CHECK-NEXT: [[TMP2:%.*]] = add i32 [[TMP0]], [[TMP0]]
; CHECK-NEXT: [[TMP3:%.*]] = icmp sgt i32 [[TMP0]], [[TMP0]]
; CHECK-NEXT: br i1 [[TMP3]], label [[BLOCK_1]], label [[BLOCK_2:%.*]]
; CHECK: block_1:
; CHECK-NEXT: [[TMP4]] = phi i32 [ [[TMP1]], [[BLOCK_0:%.*]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: call void @outlined_ir_func_0(i32 [[B]])
; CHECK-NEXT: br label [[BLOCK_0]]
; CHECK: block_2:
; CHECK-NEXT: [[TMP5:%.*]] = add i32 [[TMP2]], [[TMP2]]
; CHECK-NEXT: ret void
;
entry:
br label %block_1
block_0:
%0 = add i32 %a, %b
%1 = add i32 %4, 1
%2 = add i32 %0, %0
%3 = icmp sgt i32 %0, %0
br i1 %3, label %block_1, label %block_2
block_1:
%4 = phi i32 [ %1, %block_0 ], [ 0, %entry ]
%5 = add i32 %b, %b
br label %block_0
block_2:
%6 = add i32 %2, %2
ret void
}
define void @function2(i32 %a, i32 %b) {
; CHECK-LABEL: @function2(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[BLOCK_1:%.*]]
; CHECK: block_0:
; CHECK-NEXT: [[TMP0:%.*]] = sub i32 [[A:%.*]], [[B:%.*]]
; CHECK-NEXT: [[TMP1:%.*]] = add i32 1, [[TMP4:%.*]]
; CHECK-NEXT: [[TMP2:%.*]] = add i32 [[TMP0]], [[TMP0]]
; CHECK-NEXT: [[TMP3:%.*]] = icmp sgt i32 [[TMP0]], [[TMP0]]
; CHECK-NEXT: br i1 [[TMP3]], label [[BLOCK_1]], label [[BLOCK_2:%.*]]
; CHECK: block_1:
; CHECK-NEXT: [[TMP4]] = phi i32 [ [[TMP1]], [[BLOCK_0:%.*]] ], [ 0, [[ENTRY:%.*]] ]
; CHECK-NEXT: call void @outlined_ir_func_0(i32 [[B]])
; CHECK-NEXT: br label [[BLOCK_0]]
; CHECK: block_2:
; CHECK-NEXT: [[TMP5:%.*]] = sub i32 [[TMP2]], [[TMP2]]
; CHECK-NEXT: ret void
;
entry:
br label %block_1
block_0:
%0 = sub i32 %a, %b
%1 = add i32 1, %4
%2 = add i32 %0, %0
%3 = icmp sgt i32 %0, %0
br i1 %3, label %block_1, label %block_2
block_1:
%4 = phi i32 [ %1, %block_0 ], [ 0, %entry ]
%5 = add i32 %b, %b
br label %block_0
block_2:
%6 = sub i32 %2, %2
ret void
}