Revert "[Coverage] Fix branch coverage merging in FunctionCoverageSummary::get() for instantiation"

This reverts commit b89942c.

There are issues with this patch and also no tracking bug for it.

Author: tstellar

llvm/test/tools/llvm-cov/branch-templates.cpp

@@ -1,9 +1,9 @@
 // RUN: llvm-profdata merge %S/Inputs/branch-templates.proftext -o %t.profdata
 // RUN: llvm-cov show --show-expansions --show-branches=count %S/Inputs/branch-templates.o32l -instr-profile %t.profdata -path-equivalence=/tmp,%S %s | FileCheck %s
 // RUN: llvm-cov report --show-branch-summary %S/Inputs/branch-templates.o32l -instr-profile %t.profdata -show-functions -path-equivalence=/tmp,%S %s | FileCheck %s -check-prefix=REPORT
-// RUN: llvm-cov report --show-branch-summary %S/Inputs/branch-templates.o32l -instr-profile %t.profdata -path-equivalence=/tmp,%S %s | FileCheck %s -check-prefix=REPORTFILE
 
 #include <stdio.h>
+
 template<typename T>
 void unused(T x) {
   return;
@@ -45,17 +45,3 @@ int main() {
 // REPORT-NEXT: _Z4funcIfEiT_                     5       2  60.00%         7       3  57.14%         2       1  50.00%
 // REPORT-NEXT: ---
 // REPORT-NEXT: TOTAL                            22       7  68.18%        31      11  64.52%        12       6  50.00%
-
-// Make sure the covered branch tally for the function instantiation group is
-// merged to reflect maximum branch coverage of a single instantiation, just
-// like what is done for lines and regions. Also, the total branch tally
-// summary for an instantiation group should agree with the total number of
-// branches in the definition (In this case, 2 and 6 for func<>() and main(),
-// respectively).  This is returned by: FunctionCoverageSummary::get(const
-// InstantiationGroup &Group, ...)
-
-// REPORTFILE: Filename                      Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-// REPORTFILE-NEXT: ---
-// REPORTFILE-NEXT: branch-templates.cpp          12                 3    75.00%           2                 0   100.00%          17                 4    76.47%           8                 4    50.00%
-// REPORTFILE-NEXT: ---
-// REPORTFILE-NEXT: TOTAL                              12                 3    75.00%           2                 0   100.00%          17                 4    76.47%           8                 4    50.00%

llvm/tools/llvm-cov/CoverageSummaryInfo.cpp

@@ -100,7 +100,11 @@ FunctionCoverageSummary::get(const InstantiationGroup &Group,
   for (const auto &FCS : Summaries.drop_front()) {
     Summary.RegionCoverage.merge(FCS.RegionCoverage);
     Summary.LineCoverage.merge(FCS.LineCoverage);
-    Summary.BranchCoverage.merge(FCS.BranchCoverage);
+
+    // Sum branch coverage across instantiation groups for the summary rather
+    // than "merge" the maximum count. This is a clearer view into whether all
+    // created branches are covered.
+    Summary.BranchCoverage += FCS.BranchCoverage;
   }
   return Summary;
 }

llvm/tools/llvm-cov/CoverageSummaryInfo.h

@@ -123,11 +123,6 @@ class BranchCoverageInfo {
     return *this;
   }
 
-  void merge(const BranchCoverageInfo &RHS) {
-    Covered = std::max(Covered, RHS.Covered);
-    NumBranches = std::max(NumBranches, RHS.NumBranches);
-  }
-
   size_t getCovered() const { return Covered; }
 
   size_t getNumBranches() const { return NumBranches; }