vsk updated this revision to Diff 230714.
vsk added a comment.
- Add some documentation about clang internals.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D70571/new/
https://reviews.llvm.org/D70571
Files:
clang/docs/SourceBasedCodeCoverage.rst
clang/lib/CodeGen/CoverageMappingGen.cpp
clang/test/CoverageMapping/switch.cpp
clang/test/CoverageMapping/switchmacro.c
Index: clang/test/CoverageMapping/switchmacro.c
===================================================================
--- clang/test/CoverageMapping/switchmacro.c
+++ clang/test/CoverageMapping/switchmacro.c
@@ -4,7 +4,7 @@
// CHECK: foo
int foo(int i) { // CHECK-NEXT: File 0, [[@LINE]]:16 -> {{[0-9]+}}:2 = #0
- switch (i) {
+ switch (i) { // CHECK-NEXT: Gap,File 0, [[@LINE]]:14 -> {{[0-9]+}}:11 = 0
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: File 0, [[@LINE]]:7 -> [[@LINE]]:15 = #3
Index: clang/test/CoverageMapping/switch.cpp
===================================================================
--- clang/test/CoverageMapping/switch.cpp
+++ clang/test/CoverageMapping/switch.cpp
@@ -2,11 +2,11 @@
// CHECK: foo
void foo(int i) { // CHECK-NEXT: File 0, [[@LINE]]:17 -> [[@LINE+8]]:2 = #0
- switch(i) {
+ switch(i) { // CHECK-NEXT: Gap,File 0, [[@LINE]]:13 -> [[@LINE+4]]:10 = 0
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; // CHECK-NEXT: File 0, [[@LINE]]:10 -> [[@LINE+2]]:3 = #1
+ break; // CHECK-NEXT: Gap,File 0, [[@LINE]]:10 -> [[@LINE+2]]:3 = #1
}
int x = 0; // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:2 = #1
}
@@ -29,7 +29,7 @@
nop();
switch (i) { // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+6]]:2 = #4
- nop(); // CHECK-NEXT: File 0, [[@LINE]]:5 -> [[@LINE+2]]:10 = 0
+ nop(); // CHECK-NEXT: Gap,File 0, [[@LINE-1]]:14 -> [[@LINE+2]]:10 = 0
case 1: // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:10 = #7
nop();
}
@@ -47,7 +47,7 @@
// CHECK-NEXT: main
int main() { // CHECK-NEXT: File 0, [[@LINE]]:12 -> [[@LINE+35]]:2 = #0
int i = 0;
- switch(i) {
+ switch(i) { // CHECK-NEXT: Gap,File 0, [[@LINE]]:13 -> [[@LINE+8]]:10 = 0
case 0: // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = #2
i = 1;
break;
@@ -58,16 +58,16 @@
break; // CHECK-NEXT: File 0, [[@LINE]]:10 -> [[@LINE+2]]:3 = #1
}
switch(i) { // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+23]]:2 = #1
- case 0: // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+2]]:10 = #6
- i = 1;
+ case 0: // CHECK-NEXT: Gap,File 0, [[@LINE-1]]:13 -> [[@LINE+6]]:10 = 0
+ i = 1; // CHECK-NEXT: File 0, [[@LINE-1]]:3 -> [[@LINE+1]]:10 = #6
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; // CHECK-NEXT: File 0, [[@LINE]]:10 -> [[@LINE+3]]:3 = #5
}
-
- switch(i) { // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+13]]:2 = #5
+ // CHECK-NEXT: File 0, [[@LINE+1]]:3 -> [[@LINE+14]]:2 = #5
+ switch(i) { // CHECK-NEXT: Gap,File 0, [[@LINE]]:13 -> [[@LINE+6]]:11 = 0
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;
@@ -85,7 +85,7 @@
// 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) {
+ switch(i) { // CHECK-NEXT: Gap,File 0, [[@LINE]]:13 -> [[@LINE+9]]:10 = 0
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)
@@ -101,7 +101,7 @@
void abort(void) __attribute((noreturn));
// CHECK: noret
int noret(int x) { // CHECK-NEXT: File 0, [[@LINE]]:18 -> [[@LINE+9]]:2
- switch (x) {
+ switch (x) { // CHECK-NEXT: Gap,File 0, [[@LINE]]:14 -> [[@LINE+6]]:14 = 0
default: // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:12
abort();
case 1: // CHECK-NEXT: File 0, [[@LINE]]:3 -> [[@LINE+1]]:13
Index: clang/lib/CodeGen/CoverageMappingGen.cpp
===================================================================
--- clang/lib/CodeGen/CoverageMappingGen.cpp
+++ clang/lib/CodeGen/CoverageMappingGen.cpp
@@ -1114,8 +1114,8 @@
// 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()));
+ size_t Index = pushRegion(Counter::getZero(), getStart(CS));
+ getRegion().setGap(true);
for (const auto *Child : CS->children())
Visit(Child);
Index: clang/docs/SourceBasedCodeCoverage.rst
===================================================================
--- clang/docs/SourceBasedCodeCoverage.rst
+++ clang/docs/SourceBasedCodeCoverage.rst
@@ -302,3 +302,37 @@
If the call to ``may_throw()`` propagates an exception into ``f``, the code
coverage tool may mark the ``return`` statement as executed even though it is
not. A call to ``longjmp()`` can have similar effects.
+
+Clang implementation details
+============================
+
+This section may only be of interest to those wishing to understand or improve
+the code coverage implementation in the clang frontend.
+
+Gap regions
+-----------
+
+Gap regions are source regions with counts. A reporting tool cannot set a line
+execution count equal to the count described in a gap region unless it is the
+only region present on a line.
+
+Gap regions are used to eliminate unnatural artifacts in coverage reports, such
+as red "uncovered" highlights present at the end of an otherwise covered line,
+or blue "covered" highlights present at the start of an otherwise uncovered
+line.
+
+Switch statements
+-----------------
+
+The region mapping for a switch body consists of a gap region that covers the
+entire body (starting from the '{' in 'switch {', and terminating where the
+last case ends). The gap region has a zero count: this causes "gap" areas in
+between case statements, which contain no executable code, to appear uncovered.
+
+When a switch case is visited, the parent region is extended: if the parent
+region has no start location, its start location becomes the start of the case.
+This is used to support switch statements without a `CompoundStmt` body, in
+which the switch body and the single case share a count.
+
+For switches with `CompoundStmt` bodies, a new region is created at the start
+of each switch case.
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