Demangle dependent GNU vector extension types, Dv <expression> _ <type>.

PiperOrigin-RevId: 640993627
Change-Id: I84073099907a3634eca4b12cd2e633908465907a

2 files changed, 71 insertions, 2 deletions

diff --git a/absl/debugging/internal/demangle.cc b/absl/debugging/internal/demangle.cc
index 1a5828fa..7901a410 100644
--- a/absl/debugging/internal/demangle.cc
+++ b/absl/debugging/internal/demangle.cc
@@ -1304,7 +1304,8 @@ static bool ParseDecltype(State *state) {
 //        ::= <decltype>
 //        ::= <substitution>
 //        ::= Dp <type>          # pack expansion of (C++0x)
-//        ::= Dv <num-elems> _   # GNU vector extension
+//        ::= Dv <(elements) number> _ <type>  # GNU vector extension
+//        ::= Dv <(bytes) expression> _ <type>
 //        ::= Dk <type-constraint>  # constrained auto
 //
 static bool ParseType(State *state) {
@@ -1372,8 +1373,16 @@ static bool ParseType(State *state) {
     return true;
   }
 
+  // GNU vector extension Dv <number> _ <type>
   if (ParseTwoCharToken(state, "Dv") && ParseNumber(state, nullptr) &&
-      ParseOneCharToken(state, '_')) {
+      ParseOneCharToken(state, '_') && ParseType(state)) {
+    return true;
+  }
+  state->parse_state = copy;
+
+  // GNU vector extension Dv <expression> _ <type>
+  if (ParseTwoCharToken(state, "Dv") && ParseExpression(state) &&
+      ParseOneCharToken(state, '_') && ParseType(state)) {
     return true;
   }
   state->parse_state = copy;
diff --git a/absl/debugging/internal/demangle_test.cc b/absl/debugging/internal/demangle_test.cc
index 0b12234f..1d108c8b 100644
--- a/absl/debugging/internal/demangle_test.cc
+++ b/absl/debugging/internal/demangle_test.cc
@@ -671,6 +671,66 @@ TEST(Demangle, AbiTags) {
   EXPECT_STREQ("C[abi:bar][abi:foo]()", tmp);
 }
 
+TEST(Demangle, SimpleGnuVectorSize) {
+  char tmp[80];
+
+  // Source:
+  //
+  // #define VECTOR(size) __attribute__((vector_size(size)))
+  // void f(int x VECTOR(32)) {}
+  //
+  // The attribute's size is a number of bytes.  The compiler verifies that this
+  // value corresponds to a whole number of elements and emits the number of
+  // elements as a <number> in the mangling.  With sizeof(int) == 4, that yields
+  // 32/4 = 8.
+  //
+  // LLVM demangling:
+  //
+  // f(int vector[8])
+  EXPECT_TRUE(Demangle("_Z1fDv8_i", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f()", tmp);
+}
+
+TEST(Demangle, GnuVectorSizeIsATemplateParameter) {
+  char tmp[80];
+
+  // Source:
+  //
+  // #define VECTOR(size) __attribute__((vector_size(size)))
+  // template <int n> void f(int x VECTOR(n)) {}
+  // template void f<32>(int x VECTOR(32));
+  //
+  // LLVM demangling:
+  //
+  // void f<32>(int vector[32])
+  //
+  // Because the size was dependent on a template parameter, it was encoded
+  // using the general expression encoding.  Nothing in the mangling says how
+  // big the element type is, so the demangler is unable to show the element
+  // count 8 instead of the byte count 32.  Arguably it would have been better
+  // to make the narrow production encode the byte count, so that nondependent
+  // and dependent versions of a 32-byte vector would both come out as
+  // vector[32].
+  EXPECT_TRUE(Demangle("_Z1fILi32EEvDvT__i", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
+TEST(Demangle, GnuVectorSizeIsADependentOperatorExpression) {
+  char tmp[80];
+
+  // Source:
+  //
+  // #define VECTOR(size) __attribute__((vector_size(size)))
+  // template <int n> void f(int x VECTOR(2 * n)) {}
+  // template void f<32>(int x VECTOR(2 * 32));
+  //
+  // LLVM demangling:
+  //
+  // void f<32>(int vector[2 * 32])
+  EXPECT_TRUE(Demangle("_Z1fILi32EEvDvmlLi2ET__i", tmp, sizeof(tmp)));
+  EXPECT_STREQ("f<>()", tmp);
+}
+
 TEST(Demangle, EnableIfAttributeOnGlobalFunction) {
   char tmp[80];