[PATCH] D34801: [coverage] Make smaller regions for the first case of a switch.

[Eli Friedman via Phabricator via llvm-commits]

efriedma created this revision.

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


Repository:
  rL LLVM

https://reviews.llvm.org/D34801

Files:
  lib/CodeGen/CoverageMappingGen.cpp
  test/CoverageMapping/switch.cpp


Index: test/CoverageMapping/switch.cpp
===================================================================
--- test/CoverageMapping/switch.cpp
+++ test/CoverageMapping/switch.cpp
@@ -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 @@
 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 @@
     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 @@
   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;
+  }
+}
Index: lib/CodeGen/CoverageMappingGen.cpp
===================================================================
--- lib/CodeGen/CoverageMappingGen.cpp
+++ lib/CodeGen/CoverageMappingGen.cpp
@@ -682,6 +682,8 @@
     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);
   }
 
@@ -823,15 +825,20 @@
     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


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