[lldb] [clang] [compiler-rt] [libc] [libcxx] [flang] [clang-tools-extra] [llvm] [llvm-cov] Simplify and optimize MC/DC computation (PR #79727)
Fangrui Song via cfe-commits
cfe-commits at lists.llvm.org
Mon Jan 29 10:32:45 PST 2024
https://github.com/MaskRay updated https://github.com/llvm/llvm-project/pull/79727
>From 1d2470c2d67673f9ef9ea504e0abb3e964d43ebb Mon Sep 17 00:00:00 2001
From: Fangrui Song <i at maskray.me>
Date: Sat, 27 Jan 2024 22:24:39 -0800
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
=?UTF-8?q?l=20version?=
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Created using spr 1.3.4
---
.../ProfileData/Coverage/CoverageMapping.cpp | 133 +++++-------------
1 file changed, 35 insertions(+), 98 deletions(-)
diff --git a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
index da8e1d87319dded..16a45d1788236a0 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
@@ -286,17 +286,8 @@ class MCDCRecordProcessor {
TestVectors((size_t)1 << NumConditions) {}
private:
- void recordTestVector(MCDCRecord::TestVector &TV,
+ void recordTestVector(MCDCRecord::TestVector &TV, unsigned Index,
MCDCRecord::CondState Result) {
- // Calculate an index that is used to identify the test vector in a vector
- // of test vectors. This index also corresponds to the index values of an
- // MCDC Region's bitmap (see findExecutedTestVectors()).
- unsigned Index = 0;
- for (auto Cond = std::rbegin(TV); Cond != std::rend(TV); ++Cond) {
- Index <<= 1;
- Index |= (*Cond == MCDCRecord::MCDC_True) ? 0x1 : 0x0;
- }
-
// Copy the completed test vector to the vector of testvectors.
TestVectors[Index] = TV;
@@ -305,38 +296,25 @@ class MCDCRecordProcessor {
TestVectors[Index].push_back(Result);
}
- void shouldCopyOffTestVectorForTruePath(MCDCRecord::TestVector &TV,
- unsigned ID) {
- // Branch regions are hashed based on an ID.
- const CounterMappingRegion *Branch = Map[ID];
-
- TV[ID - 1] = MCDCRecord::MCDC_True;
- if (Branch->MCDCParams.TrueID > 0)
- buildTestVector(TV, Branch->MCDCParams.TrueID);
- else
- recordTestVector(TV, MCDCRecord::MCDC_True);
- }
-
- void shouldCopyOffTestVectorForFalsePath(MCDCRecord::TestVector &TV,
- unsigned ID) {
- // Branch regions are hashed based on an ID.
+ // Walk the binary decision tree and try assigning both false and true to each
+ // node. When a terminal node (ID == 0) is reached, fill in the value in the
+ // truth table.
+ void buildTestVector(MCDCRecord::TestVector &TV, unsigned ID,
+ unsigned Index) {
const CounterMappingRegion *Branch = Map[ID];
TV[ID - 1] = MCDCRecord::MCDC_False;
if (Branch->MCDCParams.FalseID > 0)
- buildTestVector(TV, Branch->MCDCParams.FalseID);
+ buildTestVector(TV, Branch->MCDCParams.FalseID, Index);
else
- recordTestVector(TV, MCDCRecord::MCDC_False);
- }
+ recordTestVector(TV, Index, MCDCRecord::MCDC_False);
- /// Starting with the base test vector, build a comprehensive list of
- /// possible test vectors by recursively walking the branch condition IDs
- /// provided. Once an end node is reached, record the test vector in a vector
- /// of test vectors that can be matched against during MC/DC analysis, and
- /// then reset the positions to 'DontCare'.
- void buildTestVector(MCDCRecord::TestVector &TV, unsigned ID = 1) {
- shouldCopyOffTestVectorForTruePath(TV, ID);
- shouldCopyOffTestVectorForFalsePath(TV, ID);
+ Index |= 1 << (ID - 1);
+ TV[ID - 1] = MCDCRecord::MCDC_True;
+ if (Branch->MCDCParams.TrueID > 0)
+ buildTestVector(TV, Branch->MCDCParams.TrueID, Index);
+ else
+ recordTestVector(TV, Index, MCDCRecord::MCDC_True);
// Reset back to DontCare.
TV[ID - 1] = MCDCRecord::MCDC_DontCare;
@@ -353,71 +331,30 @@ class MCDCRecordProcessor {
}
}
- /// For a given condition and two executed Test Vectors, A and B, see if the
- /// two test vectors match forming an Independence Pair for the condition.
- /// For two test vectors to match, the following must be satisfied:
- /// - The condition's value in each test vector must be opposite.
- /// - The result's value in each test vector must be opposite.
- /// - All other conditions' values must be equal or marked as "don't care".
- bool matchTestVectors(unsigned Aidx, unsigned Bidx, unsigned ConditionIdx) {
- const MCDCRecord::TestVector &A = ExecVectors[Aidx];
- const MCDCRecord::TestVector &B = ExecVectors[Bidx];
-
- // If condition values in both A and B aren't opposites, no match.
- // Because a value can be 0 (false), 1 (true), or -1 (DontCare), a check
- // that "XOR != 1" will ensure that the values are opposites and that
- // neither of them is a DontCare.
- // 1 XOR 0 == 1 | 0 XOR 0 == 0 | -1 XOR 0 == -1
- // 1 XOR 1 == 0 | 0 XOR 1 == 1 | -1 XOR 1 == -2
- // 1 XOR -1 == -2 | 0 XOR -1 == -1 | -1 XOR -1 == 0
- if ((A[ConditionIdx] ^ B[ConditionIdx]) != 1)
- return false;
-
- // If the results of both A and B aren't opposites, no match.
- if ((A[NumConditions] ^ B[NumConditions]) != 1)
- return false;
-
- for (unsigned Idx = 0; Idx < NumConditions; ++Idx) {
- // Look for other conditions that don't match. Skip over the given
- // Condition as well as any conditions marked as "don't care".
- const auto ARecordTyForCond = A[Idx];
- const auto BRecordTyForCond = B[Idx];
- if (Idx == ConditionIdx ||
- ARecordTyForCond == MCDCRecord::MCDC_DontCare ||
- BRecordTyForCond == MCDCRecord::MCDC_DontCare)
- continue;
-
- // If there is a condition mismatch with any of the other conditions,
- // there is no match for the test vectors.
- if (ARecordTyForCond != BRecordTyForCond)
- return false;
- }
-
- // Otherwise, match.
- return true;
- }
-
- /// Find all possible Independence Pairs for a boolean expression given its
- /// executed Test Vectors. This process involves looking at each condition
- /// and attempting to find two Test Vectors that "match", giving us a pair.
+ // Find an independence pair for each condition.
void findIndependencePairs() {
unsigned NumTVs = ExecVectors.size();
-
- // For each condition.
- for (unsigned C = 0; C < NumConditions; ++C) {
- bool PairFound = false;
-
- // For each executed test vector.
- for (unsigned I = 0; !PairFound && I < NumTVs; ++I) {
- // Compared to every other executed test vector.
- for (unsigned J = 0; !PairFound && J < NumTVs; ++J) {
- if (I == J)
+ for (unsigned I = 1; I < NumTVs; ++I) {
+ const MCDCRecord::TestVector &A = ExecVectors[I];
+ for (unsigned J = 0; J < I; ++J) {
+ const MCDCRecord::TestVector &B = ExecVectors[J];
+ // Enumerate two execution vectors whose outcomes are different.
+ if (A[NumConditions] == B[NumConditions])
+ continue;
+ unsigned Flip = NumConditions, Idx;
+ for (Idx = 0; Idx < NumConditions; ++Idx) {
+ MCDCRecord::CondState ACond = A[Idx], BCond = B[Idx];
+ if (ACond == BCond || ACond == MCDCRecord::MCDC_DontCare ||
+ BCond == MCDCRecord::MCDC_DontCare)
continue;
-
- // If a matching pair of vectors is found, record them.
- if ((PairFound = matchTestVectors(I, J, C)))
- IndependencePairs[C] = std::make_pair(I + 1, J + 1);
+ if (Flip != NumConditions)
+ break;
+ Flip = Idx;
}
+ // If the two vectors differ in exactly one condition, ignoring DontCare
+ // conditions, we have found an independence pair.
+ if (Idx == NumConditions && Flip != NumConditions)
+ IndependencePairs.insert({Flip, std::make_pair(J + 1, I + 1)});
}
}
}
@@ -458,7 +395,7 @@ class MCDCRecordProcessor {
MCDCRecord::TestVector TV(NumConditions, MCDCRecord::MCDC_DontCare);
// Use the base test vector to build the list of all possible test vectors.
- buildTestVector(TV);
+ buildTestVector(TV, 1, 0);
// Using Profile Bitmap from runtime, mark the executed test vectors.
findExecutedTestVectors(ExecutedTestVectorBitmap);
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