[Driver] Stop linking _p libs for -pg on FreeBSD 14

[emaste]

Summary

In FreeBSD 14 we plan to deprecate the _p.a special profiling libraries - see FreeBSD review https://reviews.freebsd.org/D30833 for details.

[dim]

I mostly agree with this, but for the "silent ignoring" of -pg which this achieves. What would be the consequence of producing an error instead, like -pg not supported for FreeBSD >= 14 ? Too many unexpected failures?

[emaste]

-pg is still supported (see the OPT_pg at line 253), gprof just won't be able to "see into" libc, libm, etc.

For example a trivial test case calling snprintf and strcmp in a loop, on FreeBSD 11 with _p libs:

  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
 57.5       0.11     0.11        0  100.00%           _mcount [1]
 14.2       0.14     0.03  1000000     0.00     0.00  __vfprintf [5]
  9.3       0.15     0.02        0  100.00%           .mcount (43)
  7.2       0.17     0.01  1000004     0.00     0.00  memset [6]
  4.0       0.18     0.01  1000000     0.00     0.00  __sfvwrite [7]
  2.6       0.18     0.01  1000000     0.00     0.00  snprintf [4]
  2.5       0.19     0.00  2000001     0.00     0.00  memcpy [8]
  1.4       0.19     0.00  1000000     0.00     0.00  localeconv_l [9]
  0.8       0.19     0.00        1     1.60    63.36  main [2]
...

Same case linking against non-_p libs:

  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
100.0       0.00     0.00        1     2.58     2.58  main [1]
  0.0       0.00     0.00        0    0.00%           _start [2]

clang/lib/Driver/ToolChains/FreeBSD.cpp

addLTOOptions(ToolChain, Args, CmdArgs, Output, Inputs[0],
                   D.getLTOMode() == LTOK_Thin);
   }
 
   bool NeedsSanitizerDeps = addSanitizerRuntimes(ToolChain, Args, CmdArgs);
   bool NeedsXRayDeps = addXRayRuntime(ToolChain, Args, CmdArgs);
   addLinkerCompressDebugSectionsOption(ToolChain, Args, CmdArgs);
   AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs, JA);
 
+  bool Profiling = Args.hasArg(options::OPT_pg) &&
+                   ToolChain.getTriple().getOSMajorVersion() < 14;
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs)) {
     // Use the static OpenMP runtime with -static-openmp
     bool StaticOpenMP = Args.hasArg(options::OPT_static_openmp) &&
                         !Args.hasArg(options::OPT_static);
     addOpenMPRuntime(CmdArgs, ToolChain, Args, StaticOpenMP);
 
     if (D.CCCIsCXX()) {
       if (ToolChain.ShouldLinkCXXStdlib(Args))
         ToolChain.AddCXXStdlibLibArgs(Args, CmdArgs);
-      if (Args.hasArg(options::OPT_pg))
+      if (Profiling)
         CmdArgs.push_back("-lm_p");
       else
         CmdArgs.push_back("-lm");
     }
     if (NeedsSanitizerDeps)
       linkSanitizerRuntimeDeps(ToolChain, CmdArgs);
     if (NeedsXRayDeps)
       linkXRayRuntimeDeps(ToolChain, CmdArgs);
     // FIXME: For some reason GCC passes -lgcc and -lgcc_s before adding
     // the default system libraries. Just mimic this for now.
-    if (Args.hasArg(options::OPT_pg))
+    if (Profiling)
       CmdArgs.push_back("-lgcc_p");
     else
       CmdArgs.push_back("-lgcc");
     if (Args.hasArg(options::OPT_static)) {
       CmdArgs.push_back("-lgcc_eh");
-    } else if (Args.hasArg(options::OPT_pg)) {
+    } else if (Profiling) {
       CmdArgs.push_back("-lgcc_eh_p");
     } else {
       CmdArgs.push_back("--as-needed");
       CmdArgs.push_back("-lgcc_s");
       CmdArgs.push_back("--no-as-needed");
     }
 
     if (Args.hasArg(options::OPT_pthread)) {
-      if (Args.hasArg(options::OPT_pg))
+      if (Profiling)
         CmdArgs.push_back("-lpthread_p");
       else
         CmdArgs.push_back("-lpthread");
     }
 
-    if (Args.hasArg(options::OPT_pg)) {
+    if (Profiling) {
       if (Args.hasArg(options::OPT_shared))
         CmdArgs.push_back("-lc");
       else
         CmdArgs.push_back("-lc_p");
       CmdArgs.push_back("-lgcc_p");
     } else {
       CmdArgs.push_back("-lc");
       CmdArgs.push_back("-lgcc");
     }
 
     if (Args.hasArg(options::OPT_static)) {
       CmdArgs.push_back("-lgcc_eh");
-    } else if (Args.hasArg(options::OPT_pg)) {
+    } else if (Profiling) {
       CmdArgs.push_back("-lgcc_eh_p");
     } else {
       CmdArgs.push_back("--as-needed");
       CmdArgs.push_back("-lgcc_s");
       CmdArgs.push_back("--no-as-needed");
     }
   }
 
void FreeBSD::addLibStdCxxIncludePaths(
     llvm::opt::ArgStringList &CC1Args) const {
   addLibStdCXXIncludePaths(getDriver().SysRoot + "/usr/include/c++/4.2", "", "",
                            DriverArgs, CC1Args);
 }
 
 void FreeBSD::AddCXXStdlibLibArgs(const ArgList &Args,
                                   ArgStringList &CmdArgs) const {
   CXXStdlibType Type = GetCXXStdlibType(Args);
-  bool Profiling = Args.hasArg(options::OPT_pg);
+  bool Profiling =
+      Args.hasArg(options::OPT_pg) && getTriple().getOSMajorVersion() < 14;
 
   switch (Type) {
   case ToolChain::CST_Libcxx:
     CmdArgs.push_back(Profiling ? "-lc++_p" : "-lc++");
     break;
 
   case ToolChain::CST_Libstdcxx:
     CmdArgs.push_back(Profiling ? "-lstdc++_p" : "-lstdc++");

clang/test/Driver/freebsd.cpp

 // RUN: %clangxx %s -### -o %t.o -target amd64-unknown-freebsd10.0 -stdlib=platform 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-TEN %s
 // RUN: %clangxx %s -### -o %t.o -target amd64-unknown-freebsd9.2 -stdlib=platform 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-NINE %s
 // CHECK-TEN: "-lc++" "-lm"
 // CHECK-NINE: "-lstdc++" "-lm"
 
+// RUN: %clangxx %s -### -pg -o %t.o -target amd64-unknown-freebsd40.0 -stdlib=platform 2>&1 \
+// RUN:   | FileCheck --check-prefix=CHECK-PG-FOURTEEN %s
 // RUN: %clangxx %s -### -pg -o %t.o -target amd64-unknown-freebsd10.0 -stdlib=platform 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-PG-TEN %s
 // RUN: %clangxx %s -### -pg -o %t.o -target amd64-unknown-freebsd9.2 -stdlib=platform 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-PG-NINE %s
+// CHECK-PG-FOURTEEN: "-lc++" "-lm"
 // CHECK-PG-TEN: "-lc++_p" "-lm_p"
 // CHECK-PG-NINE: "-lstdc++_p" "-lm_p"