[Coverage] Use gap regions to select better line exec counts

After clang started emitting deferred regions (r312818), llvm-cov has
had a hard time picking reasonable line execuction counts. There have
been one or two generic improvements in this area (e.g r310012), but
line counts can still report coverage for whitespace instead of code
(llvm.org/PR34612).

To fix the problem:

 * Introduce a new region kind so that frontends can explicitly label
   gap areas.

   This is done by changing the encoding of the columnEnd field of
   MappingRegion. This doesn't substantially increase binary size, and
   makes it easy to maintain backwards-compatibility.

 * Don't set the line count to a count from a gap area, unless the count
   comes from a wrapped segment.

 * Don't highlight gap areas as uncovered.

Fixes llvm.org/PR34612.

llvm-svn: 313597

2 files changed, 11 insertions, 21 deletions

diff --git a/llvm/test/tools/llvm-cov/Inputs/deferred-regions.covmapping b/llvm/test/tools/llvm-cov/Inputs/deferred-regions.covmapping
index 757f3eea720..4434b66513c 100644
--- a/llvm/test/tools/llvm-cov/Inputs/deferred-regions.covmapping
+++ b/llvm/test/tools/llvm-cov/Inputs/deferred-regions.covmapping
diff --git a/llvm/test/tools/llvm-cov/deferred-region.cpp b/llvm/test/tools/llvm-cov/deferred-region.cpp
index 1b191ac0f1a..6f6da7ec804 100644
--- a/llvm/test/tools/llvm-cov/deferred-region.cpp
+++ b/llvm/test/tools/llvm-cov/deferred-region.cpp
@@ -1,7 +1,7 @@
 // RUN: llvm-cov show %S/Inputs/deferred-regions.covmapping -instr-profile %S/Inputs/deferred-regions.profdata -show-line-counts-or-regions -dump -path-equivalence=/Users/vk/src/llvm.org-coverage-braces/llvm/test/tools,%S/.. %s 2>%t.markers > %t.out && FileCheck %s -input-file %t.out && FileCheck %s -input-file %t.markers -check-prefix=MARKER
 
 void foo(int x) {
-  if (x == 0) {
+  if (x == 0) { // CHECK: [[@LINE]]|{{ +}}2|
     return; // CHECK: [[@LINE]]|{{ +}}1|
   }
 
@@ -17,10 +17,10 @@ void for_loop() {
     return; // CHECK: [[@LINE]]|{{ +}}0|
 
   for (int i = 0; i < 10; ++i) { // CHECK: [[@LINE]]|{{ +}}2|
-    if (i % 2 == 0)
+    if (i % 2 == 0) // CHECK: [[@LINE]]|{{ +}}2|
       continue; // CHECK: [[@LINE]]|{{ +}}1|
 
-    if (i % 5 == 0)
+    if (i % 5 == 0) // CHECK: [[@LINE]]|{{ +}}1|
       break; // CHECK: [[@LINE]]|{{ +}}0|
 
     int x = i;
@@ -37,19 +37,19 @@ void while_loop() {
 
   int x = 0;
   while (++x < 10) { // CHECK: [[@LINE]]|{{ +}}3|
-    if (x == 1)
+    if (x == 1) // CHECK: [[@LINE]]|{{ +}}2|
       continue; // CHECK: [[@LINE]]|{{ +}}1|
 
     while (++x < 4) { // CHECK: [[@LINE]]|{{ +}}1|
-      if (x == 3)
+      if (x == 3) // CHECK: [[@LINE]]|{{ +}}1|
         break; // CHECK: [[@LINE]]|{{ +}}1|
                // CHECK: [[@LINE]]|{{ +}}0|
       while (++x < 5) {} // CHECK: [[@LINE]]|{{ +}}0|
     } // CHECK: [[@LINE]]|{{ +}}1|
 
-    if (x == 0)
+    if (x == 0) // CHECK: [[@LINE]]|{{ +}}1|
       throw Error(); // CHECK: [[@LINE]]|{{ +}}0|
-
+                // CHECK: [[@LINE]]|{{ +}}1|
     while (++x < 9) { // CHECK: [[@LINE]]|{{ +}}6|
       if (x == 0) // CHECK: [[@LINE]]|{{ +}}5|
         break; // CHECK: [[@LINE]]|{{ +}}0|
@@ -59,12 +59,12 @@ void while_loop() {
 }
 
 void gotos() {
-  if (false)
+  if (false) // CHECK: [[@LINE]]|{{ +}}1|
     goto out; // CHECK: [[@LINE]]|{{ +}}0|
+          // CHECK: [[@LINE]]|{{ +}}1|
+  return; // CHECK: [[@LINE]]|{{ +}}1|
 
-  return;
-
-out: // CHECK: [[@LINE]]|{{ +}}1|
+out: // CHECK: [[@LINE]]|{{ +}}0|
 	return;
 }
 
@@ -80,23 +80,16 @@ int main() {
 
 // MARKER: Marker at 4:7 = 2
 // MARKER-NEXT: Highlighted line 17, 5 -> 11
-// MARKER-NEXT: Marker at 17:5 = 0
 // MARKER-NEXT: Marker at 19:3 = 1
 // MARKER-NEXT: Marker at 19:19 = 2
 // MARKER-NEXT: Marker at 19:27 = 1
-// MARKER-NEXT: Marker at 21:7 = 1
 // MARKER-NEXT: Marker at 23:5 = 1
 // MARKER-NEXT: Marker at 23:9 = 1
 // MARKER-NEXT: Highlighted line 24, 7 -> 12
-// MARKER-NEXT: Marker at 24:7 = 0
 // MARKER-NEXT: Highlighted line 36, 5 -> 11
-// MARKER-NEXT: Marker at 36:5 = 0
 // MARKER-NEXT: Marker at 39:10 = 3
-// MARKER-NEXT: Marker at 41:7 = 1
 // MARKER-NEXT: Marker at 43:5 = 1
 // MARKER-NEXT: Marker at 43:12 = 1
-// MARKER-NEXT: Highlighted line 45, 14 -> ?
-// MARKER-NEXT: Marker at 45:9 = 1
 // MARKER-NEXT: Highlighted line 46, 1 -> ?
 // MARKER-NEXT: Highlighted line 47, 1 -> 7
 // MARKER-NEXT: Highlighted line 47, 7 -> 14
@@ -107,13 +100,10 @@ int main() {
 // MARKER-NEXT: Marker at 47:14 = 0
 // MARKER-NEXT: Marker at 47:23 = 0
 // MARKER-NEXT: Highlighted line 51, 7 -> 20
-// MARKER-NEXT: Marker at 51:7 = 0
 // MARKER-NEXT: Marker at 53:5 = 1
 // MARKER-NEXT: Marker at 53:12 = 6
 // MARKER-NEXT: Highlighted line 55, 9 -> 14
 // MARKER-NEXT: Highlighted line 63, 5 -> 13
-// MARKER-NEXT: Marker at 63:5 = 0
 // MARKER-NEXT: Highlighted line 67, 1 -> ?
 // MARKER-NEXT: Highlighted line 68, 1 -> 8
-// MARKER-NEXT: Highlighted line 68, 8 -> ?
 // MARKER-NEXT: Highlighted line 69, 1 -> 2