[TLI] Add support for inferring attr cold/noreturn on std::terminate and __cxa_throw

These functions are both inherently on the error path so `cold` seems
appropriate. `noreturn` is definitional.

Closes #101622

Author: goldsteinn

llvm/include/llvm/Analysis/TargetLibraryInfo.def

@@ -517,6 +517,16 @@ TLI_DEFINE_ENUM_INTERNAL(Exit)
 TLI_DEFINE_STRING_INTERNAL("_Exit")
 TLI_DEFINE_SIG_INTERNAL(Void, Int)
 
+/// void std::terminate();
+TLI_DEFINE_ENUM_INTERNAL(terminate)
+TLI_DEFINE_STRING_INTERNAL("_ZSt9terminatev")
+TLI_DEFINE_SIG_INTERNAL(Void)
+
+/// void __cxa_throw(void *, void *, void (*)(void *));
+TLI_DEFINE_ENUM_INTERNAL(cxa_throw)
+TLI_DEFINE_STRING_INTERNAL("__cxa_throw")
+TLI_DEFINE_SIG_INTERNAL(Void, Ptr, Ptr, Ptr)
+
 /// void __cxa_guard_abort(guard_t *guard);
 /// guard_t is int64_t in Itanium ABI or int32_t on ARM eabi.
 TLI_DEFINE_ENUM_INTERNAL(cxa_guard_abort)

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

@@ -50,6 +50,7 @@ STATISTIC(NumNoUndef, "Number of function returns inferred as noundef returns");
 STATISTIC(NumReturnedArg, "Number of arguments inferred as returned");
 STATISTIC(NumWillReturn, "Number of functions inferred as willreturn");
 STATISTIC(NumCold, "Number of functions inferred as cold");
+STATISTIC(NumNoReturn, "Number of functions inferred as no return");
 
 static bool setDoesNotAccessMemory(Function &F) {
   if (F.doesNotAccessMemory())
@@ -67,6 +68,14 @@ static bool setIsCold(Function &F) {
   return true;
 }
 
+static bool setNoReturn(Function &F) {
+  if (F.hasFnAttribute(Attribute::NoReturn))
+    return false;
+  F.addFnAttr(Attribute::NoReturn);
+  ++NumNoReturn;
+  return true;
+}
+
 static bool setOnlyAccessesInaccessibleMemory(Function &F) {
   if (F.onlyAccessesInaccessibleMemory())
     return false;
@@ -1103,6 +1112,15 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_abort:
     Changed |= setIsCold(F);
     break;
+  case LibFunc_terminate:
+    Changed |= setIsCold(F);
+    Changed |= setNoReturn(F);
+    break;
+  case LibFunc_cxa_throw:
+    Changed |= setIsCold(F);
+    Changed |= setNoReturn(F);
+    // Don't add `nofree` on `__cxa_throw`
+    return Changed;
   // int __nvvm_reflect(const char *)
   case LibFunc_nvvm_reflect:
     Changed |= setRetAndArgsNoUndef(F);

llvm/test/Transforms/InferFunctionAttrs/annotate.ll

@@ -1100,6 +1100,12 @@ declare i64 @write(i32, ptr, i64)
 ; CHECK: declare void @abort() [[NOFREE_COLD:#[0-9]+]]
 declare void @abort()
 
+; CHECK: declare void @__cxa_throw(ptr, ptr, ptr) [[COLD_NORETURN:#[0-9]+]]
+declare void @__cxa_throw(ptr, ptr, ptr)
+
+; CHECK: declare void @_ZSt9terminatev() [[NOFREE_COLD_NORETURN:#[0-9]+]]
+declare void @_ZSt9terminatev()
+
 ; memset_pattern{4,8,16} aren't available everywhere.
 ; CHECK-DARWIN: declare void @memset_pattern4(ptr nocapture writeonly, ptr nocapture readonly, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
 declare void @memset_pattern4(ptr, ptr, i64)
@@ -1126,6 +1132,8 @@ declare void @memset_pattern16(ptr, ptr, i64)
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGMEMONLY_NOUNWIND_WILLRETURN_ALLOCKIND_REALLOC_ALLOCSIZE1_FAMILY_MALLOC]] = { mustprogress nounwind willreturn allockind("realloc") allocsize(1) memory(argmem: readwrite, inaccessiblemem: readwrite) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND_WILLRETURN_FAMILY_MALLOC]] = { mustprogress nofree nounwind willreturn memory(argmem: readwrite, inaccessiblemem: readwrite) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[NOFREE_COLD]] = { cold nofree }
+; CHECK-DAG: attributes [[NOFREE_COLD_NORETURN]] = { cold nofree noreturn }
+; CHECK-DAG: attributes [[COLD_NORETURN]] = { cold noreturn }
 
 ; CHECK-NVPTX-DAG: attributes [[NOFREE_NOUNWIND_READNONE]] = { nofree nosync nounwind memory(none) }
 

llvm/test/tools/llvm-tli-checker/ps4-tli-check.yaml

@@ -34,7 +34,7 @@
 #
 # CHECK: << Total TLI yes SDK no:  18
 # CHECK: >> Total TLI no  SDK yes: 0
-# CHECK: == Total TLI yes SDK yes: 248
+# CHECK: == Total TLI yes SDK yes: 250
 #
 # WRONG_DETAIL: << TLI yes SDK no : '_ZdaPv' aka operator delete[](void*)
 # WRONG_DETAIL: >> TLI no  SDK yes: '_ZdaPvj' aka operator delete[](void*, unsigned int)
@@ -48,14 +48,14 @@
 # WRONG_DETAIL: << TLI yes SDK no : 'fminimum_numl'
 # WRONG_SUMMARY: << Total TLI yes SDK no:  19{{$}}
 # WRONG_SUMMARY: >> Total TLI no  SDK yes: 1{{$}}
-# WRONG_SUMMARY: == Total TLI yes SDK yes: 247
+# WRONG_SUMMARY: == Total TLI yes SDK yes: 249
 #
 ## The -COUNT suffix doesn't care if there are too many matches, so check
 ## the exact count first; the two directives should add up to that.
 ## Yes, this means additions to TLI will fail this test, but the argument
 ## to -COUNT can't be an expression.
-# AVAIL: TLI knows 499 symbols, 266 available
-# AVAIL-COUNT-266: {{^}} available
+# AVAIL: TLI knows 501 symbols, 268 available
+# AVAIL-COUNT-268: {{^}} available
 # AVAIL-NOT:       {{^}} available
 # UNAVAIL-COUNT-233: not available
 # UNAVAIL-NOT:       not available
@@ -174,6 +174,10 @@ DynamicSymbols:
     Type:            STT_FUNC
     Section:         .text
     Binding:         STB_GLOBAL
+  - Name:            __cxa_throw
+    Type:            STT_FUNC
+    Section:         .text
+    Binding:         STB_GLOBAL
   - Name:            __cxa_guard_release
     Type:            STT_FUNC
     Section:         .text
@@ -286,6 +290,10 @@ DynamicSymbols:
     Type:            STT_FUNC
     Section:         .text
     Binding:         STB_GLOBAL
+  - Name:            _ZSt9terminatev
+    Type:            STT_FUNC
+    Section:         .text
+    Binding:         STB_GLOBAL
   - Name:            atof
     Type:            STT_FUNC
     Section:         .text

llvm/unittests/Analysis/TargetLibraryInfoTest.cpp

@@ -535,12 +535,14 @@ TEST_F(TargetLibraryInfoTest, ValidProto) {
       "declare void @__cxa_guard_abort(%struct*)\n"
       "declare i32 @__cxa_guard_acquire(%struct*)\n"
       "declare void @__cxa_guard_release(%struct*)\n"
+      "declare void @__cxa_throw(ptr, ptr, ptr)\n"
 
       "declare i32 @atexit(void ()*)\n"
 
       "declare void @abort()\n"
       "declare void @exit(i32)\n"
       "declare void @_Exit(i32)\n"
+      "declare void @_ZSt9terminatev()\n"
 
       "declare i32 @__nvvm_reflect(i8*)\n"