lld: Reduce number of references to undefined printed from 10 to 3.

As of a while ago, lld groups all undefined references to a single
symbol in a single diagnostic. Back then, I made it so that we
print up to 10 references to each undefined symbol.

Having used this for a while, I never wished there were more
references, but I sometimes found that this can print a lot of
output. lld prints up to 10 diagnostics by default, and if
each has 10 references (which I've seen in practice), and each
undefined symbol produces 2 (possibly very long) lines of output,
that's over 200 lines of error output.

Let's try it with just 3 references for a while and see how
that feels in practice.

Differential Revision: https://reviews.llvm.org/D77017

Author: nico

lld/COFF/SymbolTable.cpp

@@ -204,7 +204,7 @@ static void reportUndefinedSymbol(const UndefinedDiag &undefDiag) {
   llvm::raw_string_ostream os(out);
   os << "undefined symbol: " << toString(*undefDiag.sym);
 
-  const size_t maxUndefReferences = 10;
+  const size_t maxUndefReferences = 3;
   size_t i = 0, numRefs = 0;
   for (const UndefinedDiag::File &ref : undefDiag.files) {
     std::vector<std::string> symbolLocations =

lld/ELF/Relocations.cpp

@@ -870,7 +870,7 @@ static void reportUndefinedSymbol(const UndefinedDiag &undef,
   if (msg.empty())
     msg = "undefined " + visibility() + "symbol: " + toString(sym);
 
-  const size_t maxUndefReferences = 10;
+  const size_t maxUndefReferences = 3;
   size_t i = 0;
   for (UndefinedDiag::Loc l : undef.locs) {
     if (i >= maxUndefReferences)

lld/test/COFF/undefined-symbol-multi.s

@@ -22,14 +22,7 @@
 # CHECK-NEXT: >>> referenced by {{.*}}tmp.obj:(main)
 # CHECK-NEXT: >>> referenced by {{.*}}tmp.obj:(main)
 # CHECK-NEXT: >>> referenced by {{.*}}tmp2.obj:(bar)
-# CHECK-NEXT: >>> referenced by {{.*}}tmp2.obj:(bar)
-# CHECK-NEXT: >>> referenced by {{.*}}tmp2.obj:(bar)
-# CHECK-NEXT: >>> referenced by {{.*}}tmp2.obj:(bar)
-# CHECK-NEXT: >>> referenced by {{.*}}tmp2.obj:(bar)
-# CHECK-NEXT: >>> referenced by {{.*}}tmp2.obj:(bar)
-# CHECK-NEXT: >>> referenced by {{.*}}tmp2.obj:(bar)
-# CHECK-NEXT: >>> referenced by {{.*}}tmp2.obj:(bar)
-# CHECK-NEXT: >>> referenced 2 more times
+# CHECK-NEXT: >>> referenced 9 more times
 # CHECK-EMPTY:
 # CHECK-NEXT: error: undefined symbol: int __cdecl bar(void)
 # CHECK-NEXT: >>> referenced by {{.*}}.obj:(main)

lld/test/ELF/undef-multi.s

@@ -10,9 +10,7 @@
 # CHECK-NEXT: >>>               {{.*}}:(.text+0x6)
 # CHECK-NEXT: >>> referenced by undef-multi.s
 # CHECK-NEXT: >>>               {{.*}}:(.text+0xB)
-# CHECK-NEXT: >>> referenced by undef-multi.s
-# CHECK-NEXT: >>>               {{.*}}:(.text+0x10)
-# CHECK-NEXT: >>> referenced by {{.*}}tmp2.o:(.text+0x0)
+# CHECK-NEXT: >>> referenced 2 more times
 
 # All references to a single undefined symbol count as a single error -- but
 # at most 10 references are printed.
@@ -36,15 +34,7 @@
 # LIMIT-NEXT: >>>               {{.*}}:(.text+0x6)
 # LIMIT-NEXT: >>> referenced by undef-multi.s
 # LIMIT-NEXT: >>>               {{.*}}:(.text+0xB)
-# LIMIT-NEXT: >>> referenced by undef-multi.s
-# LIMIT-NEXT: >>>               {{.*}}:(.text+0x10)
-# LIMIT-NEXT: >>> referenced by {{.*}}tmp2.o:(.text+0x0)
-# LIMIT-NEXT: >>> referenced by {{.*}}tmp3.o:(.text+0x1)
-# LIMIT-NEXT: >>> referenced by {{.*}}tmp3.o:(.text+0x6)
-# LIMIT-NEXT: >>> referenced by {{.*}}tmp3.o:(.text+0xB)
-# LIMIT-NEXT: >>> referenced by {{.*}}tmp3.o:(.text+0x10)
-# LIMIT-NEXT: >>> referenced by {{.*}}tmp3.o:(.text+0x15)
-# LIMIT-NEXT: >>> referenced 2 more times
+# LIMIT-NEXT: >>> referenced 9 more times
 
 .file "undef-multi.s"