[InferAttrs] Mark floating-point libcalls as errno-writing

Floating-point libcalls are currently conservatively marked as
may write any memory. Restrict these to clobber only `errno`.

Author: antoniofrighetto

llvm/include/llvm/IR/Function.h

@@ -571,7 +571,7 @@ class LLVM_ABI Function : public GlobalObject, public ilist_node<Function> {
   bool onlyWritesMemory() const;
   void setOnlyWritesMemory();
 
-  /// Determine if the call can access memmory only using pointers based
+  /// Determine if the call can access memory only using pointers based
   /// on its arguments.
   bool onlyAccessesArgMemory() const;
   void setOnlyAccessesArgMemory();
@@ -581,6 +581,10 @@ class LLVM_ABI Function : public GlobalObject, public ilist_node<Function> {
   bool onlyAccessesInaccessibleMemory() const;
   void setOnlyAccessesInaccessibleMemory();
 
+  /// Determine if the call can access only errno memory.
+  bool onlyAccessesErrnoMemory() const;
+  void setOnlyAccessesErrnoMemory();
+
   /// Determine if the function may only access memory that is
   ///  either inaccessible from the IR or pointed to by its arguments.
   bool onlyAccessesInaccessibleMemOrArgMem() const;

llvm/lib/IR/Function.cpp

@@ -904,7 +904,7 @@ void Function::setOnlyWritesMemory() {
   setMemoryEffects(getMemoryEffects() & MemoryEffects::writeOnly());
 }
 
-/// Determine if the call can access memmory only using pointers based
+/// Determine if the call can access memory only using pointers based
 /// on its arguments.
 bool Function::onlyAccessesArgMemory() const {
   return getMemoryEffects().onlyAccessesArgPointees();
@@ -922,6 +922,14 @@ void Function::setOnlyAccessesInaccessibleMemory() {
   setMemoryEffects(getMemoryEffects() & MemoryEffects::inaccessibleMemOnly());
 }
 
+/// Determine if the call can access only errno memory.
+bool Function::onlyAccessesErrnoMemory() const {
+  return getMemoryEffects().onlyAccessesErrnoMem();
+}
+void Function::setOnlyAccessesErrnoMemory() {
+  setMemoryEffects(getMemoryEffects() & MemoryEffects::errnoMemOnly());
+}
+
 /// Determine if the function may only access memory that is
 ///  either inaccessible from the IR or pointed to by its arguments.
 bool Function::onlyAccessesInaccessibleMemOrArgMem() const {

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

@@ -39,6 +39,7 @@ STATISTIC(NumInaccessibleMemOnly,
 STATISTIC(NumReadOnly, "Number of functions inferred as readonly");
 STATISTIC(NumWriteOnly, "Number of functions inferred as writeonly");
 STATISTIC(NumArgMemOnly, "Number of functions inferred as argmemonly");
+STATISTIC(NumErrnoMemOnly, "Number of functions inferred as errnomemonly");
 STATISTIC(NumInaccessibleMemOrArgMemOnly,
           "Number of functions inferred as inaccessiblemem_or_argmemonly");
 STATISTIC(NumNoUnwind, "Number of functions inferred as nounwind");
@@ -84,6 +85,14 @@ static bool setOnlyAccessesInaccessibleMemory(Function &F) {
   return true;
 }
 
+static bool setOnlyAccessesErrnoMemory(Function &F) {
+  if (F.onlyAccessesErrnoMemory())
+    return false;
+  F.setOnlyAccessesErrnoMemory();
+  ++NumErrnoMemOnly;
+  return true;
+}
+
 static bool setOnlyReadsMemory(Function &F) {
   if (F.onlyReadsMemory())
     return false;
@@ -1145,14 +1154,14 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_ldexp:
   case LibFunc_ldexpf:
   case LibFunc_ldexpl:
+    Changed |= setOnlyAccessesErrnoMemory(F);
     Changed |= setWillReturn(F);
     break;
   case LibFunc_remquo:
   case LibFunc_remquof:
   case LibFunc_remquol:
     Changed |= setDoesNotCapture(F, 2);
     [[fallthrough]];
-  case LibFunc_abs:
   case LibFunc_acos:
   case LibFunc_acosf:
   case LibFunc_acosh:
@@ -1174,15 +1183,9 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_atanhf:
   case LibFunc_atanhl:
   case LibFunc_atanl:
-  case LibFunc_cbrt:
-  case LibFunc_cbrtf:
-  case LibFunc_cbrtl:
   case LibFunc_ceil:
   case LibFunc_ceilf:
   case LibFunc_ceill:
-  case LibFunc_copysign:
-  case LibFunc_copysignf:
-  case LibFunc_copysignl:
   case LibFunc_cos:
   case LibFunc_cosh:
   case LibFunc_coshf:
@@ -1206,37 +1209,18 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_expm1:
   case LibFunc_expm1f:
   case LibFunc_expm1l:
-  case LibFunc_fabs:
-  case LibFunc_fabsf:
-  case LibFunc_fabsl:
   case LibFunc_fdim:
   case LibFunc_fdiml:
   case LibFunc_fdimf:
-  case LibFunc_ffs:
-  case LibFunc_ffsl:
-  case LibFunc_ffsll:
   case LibFunc_floor:
   case LibFunc_floorf:
   case LibFunc_floorl:
-  case LibFunc_fls:
-  case LibFunc_flsl:
-  case LibFunc_flsll:
-  case LibFunc_fmax:
-  case LibFunc_fmaxf:
-  case LibFunc_fmaxl:
-  case LibFunc_fmin:
-  case LibFunc_fminf:
-  case LibFunc_fminl:
   case LibFunc_fmod:
   case LibFunc_fmodf:
   case LibFunc_fmodl:
   case LibFunc_hypot:
   case LibFunc_hypotf:
   case LibFunc_hypotl:
-  case LibFunc_isascii:
-  case LibFunc_isdigit:
-  case LibFunc_labs:
-  case LibFunc_llabs:
   case LibFunc_log:
   case LibFunc_log10:
   case LibFunc_log10f:
@@ -1294,26 +1278,53 @@ bool llvm::inferNonMandatoryLibFuncAttrs(Function &F,
   case LibFunc_tanhf:
   case LibFunc_tanhl:
   case LibFunc_tanl:
+    Changed |= setOnlyAccessesErrnoMemory(F);
+    [[fallthrough]];
+  case LibFunc_abs:
+  case LibFunc_cbrt:
+  case LibFunc_cbrtf:
+  case LibFunc_cbrtl:
+  case LibFunc_copysign:
+  case LibFunc_copysignf:
+  case LibFunc_copysignl:
+  case LibFunc_fabs:
+  case LibFunc_fabsf:
+  case LibFunc_fabsl:
+  case LibFunc_ffs:
+  case LibFunc_ffsl:
+  case LibFunc_ffsll:
+  case LibFunc_fls:
+  case LibFunc_flsl:
+  case LibFunc_flsll:
+  case LibFunc_fmax:
+  case LibFunc_fmaxf:
+  case LibFunc_fmaxl:
+  case LibFunc_fmin:
+  case LibFunc_fminf:
+  case LibFunc_fminl:
+  case LibFunc_isascii:
+  case LibFunc_isdigit:
+  case LibFunc_labs:
+  case LibFunc_llabs:
   case LibFunc_toascii:
   case LibFunc_trunc:
   case LibFunc_truncf:
   case LibFunc_truncl:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotFreeMemory(F);
-    Changed |= setOnlyWritesMemory(F);
     Changed |= setWillReturn(F);
     break;
   case LibFunc_sincos:
   case LibFunc_sincosf:
   case LibFunc_sincosl:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotFreeMemory(F);
-    Changed |= setOnlyWritesMemory(F);
     Changed |= setOnlyWritesMemory(F, 1);
     Changed |= setOnlyWritesMemory(F, 2);
     Changed |= setDoesNotCapture(F, 1);
     Changed |= setDoesNotCapture(F, 2);
     Changed |= setWillReturn(F);
+    Changed |= setOnlyAccessesErrnoMemory(F);
     break;
   default:
     // FIXME: It'd be really nice to cover all the library functions we're