r309901 - [coverage] Make smaller regions for the first case of a switch.

[Eli Friedman via cfe-commits]

Author: efriedma
Date: Wed Aug  2 16:22:50 2017
New Revision: 309901

URL: http://llvm.org/viewvc/llvm-project?rev=309901&view=rev
Log:
[coverage] Make smaller regions for the first case of a switch.

We never overwrite the end location of a region, so we would end up with
an overly large region when we reused the switch's region.

It's possible this code will be substantially rewritten in the near
future to deal with fallthrough more accurately, but this seems like
an improvement on its own for now.

Differential Revision: https://reviews.llvm.org/D34801


Modified:
    cfe/trunk/lib/CodeGen/CoverageMappingGen.cpp
    cfe/trunk/test/CoverageMapping/switch.cpp

Modified: cfe/trunk/lib/CodeGen/CoverageMappingGen.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CoverageMappingGen.cpp?rev=309901&r1=309900&r2=309901&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CoverageMappingGen.cpp (original)
+++ cfe/trunk/lib/CodeGen/CoverageMappingGen.cpp Wed Aug  2 16:22:50 2017
@@ -704,6 +704,8 @@ struct CounterCoverageMappingBuilder
     assert(!BreakContinueStack.empty() && "break not in a loop or switch!");
     BreakContinueStack.back().BreakCount = addCounters(
         BreakContinueStack.back().BreakCount, getRegion().getCounter());
+    // FIXME: a break in a switch should terminate regions for all preceding
+    // case statements, not just the most recent one.
     terminateRegion(S);
   }
 
@@ -845,15 +847,20 @@ struct CounterCoverageMappingBuilder
     extendRegion(Body);
     if (const auto *CS = dyn_cast<CompoundStmt>(Body)) {
       if (!CS->body_empty()) {
-        // The body of the switch needs a zero region so that fallthrough counts
-        // behave correctly, but it would be misleading to include the braces of
-        // the compound statement in the zeroed area, so we need to handle this
-        // specially.
+        // Make a region for the body of the switch.  If the body starts with
+        // a case, that case will reuse this region; otherwise, this covers
+        // the unreachable code at the beginning of the switch body.
         size_t Index =
-            pushRegion(Counter::getZero(), getStart(CS->body_front()),
-                       getEnd(CS->body_back()));
+            pushRegion(Counter::getZero(), getStart(CS->body_front()));
         for (const auto *Child : CS->children())
           Visit(Child);
+
+        // Set the end for the body of the switch, if it isn't already set.
+        for (size_t i = RegionStack.size(); i != Index; --i) {
+          if (!RegionStack[i - 1].hasEndLoc())
+            RegionStack[i - 1].setEndLoc(getEnd(CS->body_back()));
+        }
+
         popRegions(Index);
       }
     } else

Modified: cfe/trunk/test/CoverageMapping/switch.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CoverageMapping/switch.cpp?rev=309901&r1=309900&r2=309901&view=diff
==============================================================================
--- cfe/trunk/test/CoverageMapping/switch.cpp (original)
+++ cfe/trunk/test/CoverageMapping/switch.cpp Wed Aug  2 16:22:50 2017
@@ -3,7 +3,7 @@
                     // CHECK: foo
 void foo(int i) {   // CHECK-NEXT: File 0, [[@LINE]]:17 -> [[@LINE+8]]:2 = #0
   switch(i) {
-  case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+3]]:10 = #2
+  case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:11 = #2
     return;
   case 2:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:10 = #3
     break;
@@ -48,7 +48,7 @@ void baz() {        // CHECK-NEXT: File
 int main() {        // CHECK-NEXT: File 0, [[@LINE]]:12 -> [[@LINE+35]]:2 = #0
   int i = 0;
   switch(i) {
-  case 0:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+7]]:10 = #2
+  case 0:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = #2
     i = 1;
     break;
   case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = #3
@@ -58,7 +58,7 @@ int main() {        // CHECK-NEXT: File
     break;
   }
   switch(i) {       // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+23]]:2 = #1
-  case 0:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+6]]:10 = #6
+  case 0:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = #6
     i = 1;
     break;
   case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+3]]:10 = #7
@@ -81,3 +81,19 @@ int main() {        // CHECK-NEXT: File
   baz();
   return 0;
 }
+
+// FIXME: End location for "case 1" shouldn't point at the end of the switch.
+                         // CHECK: fallthrough
+int fallthrough(int i) { // CHECK-NEXT: File 0, [[@LINE]]:24 -> [[@LINE+12]]:2 = #0
+  switch(i) {
+  case 1:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+8]]:10 = #2
+    i = 23;
+  case 2:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = (#2 + #3)
+    i = 11;
+    break;
+  case 3:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+3]]:10 = #4
+  case 4:           // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = (#4 + #5)
+    i = 99;
+    break;
+  }
+}