[Coverage] The coverage region for a switch should cover the code after the switch

[arphaman]

Summary

This patch fixes a regression introduced in r262697 that changed the way the coverage regions for switch are constructed. The PGO instrumentation counter for switch statements refers to a counter at the exit of the switch, and thus the coverage region for the switch statement should cover the code that comes after the switch, and not the switch statement itself.

This patch should fix the issue exposed by the new coverage bot where the switches with all cases returning get zero coverage: http://lab.llvm.org:8080/coverage/coverage-reports/clang/coverage/Users/buildslave/jenkins/sharedspace/clang-stage2-coverage-R@2/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp.html#L520.

[vsk]

LGTM, thank you!

It makes sense to inherit the current region's counter when we see a new switch. That should fix the 0 execution count we see on the condition.

cfe/trunk/lib/CodeGen/CoverageMappingGen.cpp

void VisitSwitchStmt(const SwitchStmt *S) {
     BreakContinue BC = BreakContinueStack.pop_back_val();
 
     if (!BreakContinueStack.empty())
       BreakContinueStack.back().ContinueCount = addCounters(
           BreakContinueStack.back().ContinueCount, BC.ContinueCount);
 
     Counter ExitCount = getRegionCounter(S);
     SourceLocation ExitLoc = getEnd(S);
-    pushRegion(ExitCount, getStart(S), ExitLoc);
+    pushRegion(ExitCount);
+
+    // Ensure that handleFileExit recognizes when the end location is located
+    // in a different file.
+    MostRecentLocation = getStart(S);
     handleFileExit(ExitLoc);
   }
 
   void VisitSwitchCase(const SwitchCase *S) {
     extendRegion(S);
 
     SourceMappingRegion &Parent = getRegion();
 

cfe/trunk/test/CoverageMapping/switch.c

 // RUN: %clang_cc1 -fprofile-instrument=clang -fcoverage-mapping -dump-coverage-mapping -emit-llvm-only -main-file-name switch.c %s | FileCheck %s
                     // CHECK: foo
 void foo(int i) {   // CHECK-NEXT: File 0, [[@LINE]]:17 -> [[@LINE+8]]:2 = #0
-  switch(i) {       // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+5]]:4 = #1
+  switch(i) {
   case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+3]]:10 = #2
     return;
   case 2:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:10 = #3
     break;
   }
-  int x = 0;
+  int x = 0;        // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:2 = #1
 }
 
 void nop() {}
 
                     // CHECK: bar
 void bar(int i) {   // CHECK-NEXT: File 0, [[@LINE]]:17 -> [[@LINE+20]]:2 = #0
-  switch (i)        // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:6 = #1
+  switch (i)
     ;               // CHECK-NEXT: File 0, [[@LINE]]:5 -> [[@LINE]]:6 = 0
 
-  switch (i) {      // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:4 = #2
+  switch (i) {      // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+16]]:2 = #1
   }
 
-  switch (i)        // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:10 = #3
+  switch (i)        // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+13]]:2 = #2
     nop();          // CHECK-NEXT: File 0, [[@LINE]]:5 -> [[@LINE]]:10 = 0
 
-  switch (i)        // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = #4
+  switch (i)        // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+10]]:2 = #3
   case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:10 = #5
     nop();
 
-  switch (i) {      // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+4]]:4 = #6
+  switch (i) {      // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+6]]:2 = #4
     nop();          // CHECK-NEXT: File 0, [[@LINE]]:5 -> [[@LINE+2]]:10 = 0
   case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:10 = #7
     nop();
   }
-  nop();
+  nop();            // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:2 = #6
 }
 
                     // CHECK-NEXT: main
 int main() {        // CHECK-NEXT: File 0, [[@LINE]]:12 -> [[@LINE+34]]:2 = #0
   int i = 0;
-  switch(i) {       // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+9]]:4 = #1
+  switch(i) {
   case 0:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+7]]:10 = #2
     i = 1;
     break;
   case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = #3
     i = 2;
     break;
   default:          // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:10 = #4
     break;
   }
-  switch(i) {       // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+8]]:4 = #5
+  switch(i) {       // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+22]]:2 = #1
   case 0:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+6]]:10 = #6
     i = 1;
     break;
   case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+3]]:10 = #7
     i = 2;
   default:          // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:10 = (#7 + #8)
     break;
   }
 
-  switch(i) {       // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+7]]:4 = #9
+  switch(i) {       // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+12]]:2 = #5
   case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+5]]:11 = #10
   case 2:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+4]]:11 = (#10 + #11)
     i = 11;
   case 3:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:11 = ((#10 + #11) + #12)
   case 4:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:11 = (((#10 + #11) + #12) + #13)
     i = 99;
   }
 
-  foo(1);
+  foo(1);           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:11 = #9
   bar(1);
   return 0;
 }

cfe/trunk/test/CoverageMapping/switchmacro.c

 // RUN: %clang_cc1 -fprofile-instrument=clang -fcoverage-mapping -dump-coverage-mapping -emit-llvm-only -main-file-name switchmacro.c %s | FileCheck %s
 
 #define FOO(x) (void)x
 
 // CHECK: foo
 int foo(int i) { // CHECK-NEXT: File 0, [[@LINE]]:16 -> {{[0-9]+}}:2 = #0
-  switch (i) {   // CHECK-NEXT: File 0, [[@LINE]]:3 -> {{[0-9]+}}:4 = #1
+  switch (i) {
   default:       // CHECK-NEXT: File 0, [[@LINE]]:3 -> {{[0-9]+}}:11 = #2
     if (i == 1)  // CHECK-NEXT: File 0, [[@LINE]]:9 -> [[@LINE]]:15 = #2
       return 0;  // CHECK-NEXT: File 0, [[@LINE]]:7 -> [[@LINE]]:15 = #3
     // CHECK-NEXT: Expansion,File 0, [[@LINE+2]]:5 -> [[@LINE+2]]:8 = (#2 - #3) (Expanded file = 1)
     // CHECK-NEXT: File 0, [[@LINE+1]]:8 -> {{[0-9]+}}:11 = (#2 - #3)
     FOO(1);
   case 0:        // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:13 = ((#2 + #4) - #3)
     return 2;