Mark @llvm.trap cold

A call to @llvm.trap can be expected to be cold (i.e. unlikely to be
reached in a normal program execution).

Outlining paths which unconditionally trap is an important memory
saving. As the hot/cold splitting pass (imho) should not treat all
noreturn calls as cold, explicitly mark @llvm.trap cold so that it can
be outlined.

Split out of https://reviews.llvm.org/D54244.

Differential Revision: https://reviews.llvm.org/D54329

llvm-svn: 346885

7 files changed, 24 insertions, 5 deletions

diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index 06e092fb9fc..739267c8f58 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -14868,7 +14868,7 @@ Syntax:
 
 ::
 
-      declare void @llvm.trap() noreturn nounwind
+      declare void @llvm.trap() cold noreturn nounwind
 
 Overview:
 """""""""
diff --git a/llvm/include/llvm/IR/Intrinsics.td b/llvm/include/llvm/IR/Intrinsics.td
index 04de1ca63a2..4213d750b3f 100644
--- a/llvm/include/llvm/IR/Intrinsics.td
+++ b/llvm/include/llvm/IR/Intrinsics.td
@@ -90,6 +90,10 @@ class ReadNone<int argNo> : IntrinsicProperty {
 
 def IntrNoReturn : IntrinsicProperty;
 
+// IntrCold - Calls to this intrinsic are cold.
+// Parallels the cold attribute on LLVM IR functions.
+def IntrCold : IntrinsicProperty;
+
 // IntrNoduplicate - Calls to this intrinsic cannot be duplicated.
 // Parallels the noduplicate attribute on LLVM IR functions.
 def IntrNoDuplicate : IntrinsicProperty;
@@ -867,7 +871,7 @@ def int_coro_subfn_addr : Intrinsic<[llvm_ptr_ty], [llvm_ptr_ty, llvm_i8_ty],
 //
 def int_flt_rounds : Intrinsic<[llvm_i32_ty]>,
                      GCCBuiltin<"__builtin_flt_rounds">;
-def int_trap : Intrinsic<[], [], [IntrNoReturn]>,
+def int_trap : Intrinsic<[], [], [IntrNoReturn, IntrCold]>,
                GCCBuiltin<"__builtin_trap">;
 def int_debugtrap : Intrinsic<[]>,
                     GCCBuiltin<"__builtin_debugtrap">;
diff --git a/llvm/test/Feature/intrinsics.ll b/llvm/test/Feature/intrinsics.ll
index bbf30d3cc23..71bb73cde18 100644
--- a/llvm/test/Feature/intrinsics.ll
+++ b/llvm/test/Feature/intrinsics.ll
@@ -70,4 +70,4 @@ define void @trap() {
 }
 
 ; CHECK: attributes #0 = { nounwind readnone speculatable }
-; CHECK: attributes #1 = { noreturn nounwind }
+; CHECK: attributes #1 = { cold noreturn nounwind }
diff --git a/llvm/test/Transforms/SimplifyCFG/switch-on-const-select.ll b/llvm/test/Transforms/SimplifyCFG/switch-on-const-select.ll
index c33030fa5d1..165e5b264ae 100644
--- a/llvm/test/Transforms/SimplifyCFG/switch-on-const-select.ll
+++ b/llvm/test/Transforms/SimplifyCFG/switch-on-const-select.ll
@@ -138,4 +138,4 @@ declare void @bees.a() nounwind
 declare void @bees.b() nounwind
 
 ; CHECK: attributes [[$NUW]] = { nounwind }
-; CHECK: attributes #1 = { noreturn nounwind }
+; CHECK: attributes #1 = { cold noreturn nounwind }
diff --git a/llvm/utils/TableGen/CodeGenIntrinsics.h b/llvm/utils/TableGen/CodeGenIntrinsics.h
index 5d071595912..9487a79c143 100644
--- a/llvm/utils/TableGen/CodeGenIntrinsics.h
+++ b/llvm/utils/TableGen/CodeGenIntrinsics.h
@@ -124,6 +124,9 @@ struct CodeGenIntrinsic {
   /// True if the intrinsic is no-return.
   bool isNoReturn;
 
+  /// True if the intrinsic is cold.
+  bool isCold;
+
   /// True if the intrinsic is marked as convergent.
   bool isConvergent;
 
diff --git a/llvm/utils/TableGen/CodeGenTarget.cpp b/llvm/utils/TableGen/CodeGenTarget.cpp
index 305d2d19ff4..bcb65313555 100644
--- a/llvm/utils/TableGen/CodeGenTarget.cpp
+++ b/llvm/utils/TableGen/CodeGenTarget.cpp
@@ -536,6 +536,7 @@ CodeGenIntrinsic::CodeGenIntrinsic(Record *R) {
   isCommutative = false;
   canThrow = false;
   isNoReturn = false;
+  isCold = false;
   isNoDuplicate = false;
   isConvergent = false;
   isSpeculatable = false;
@@ -682,6 +683,8 @@ CodeGenIntrinsic::CodeGenIntrinsic(Record *R) {
       isConvergent = true;
     else if (Property->getName() == "IntrNoReturn")
       isNoReturn = true;
+    else if (Property->getName() == "IntrCold")
+      isCold = true;
     else if (Property->getName() == "IntrSpeculatable")
       isSpeculatable = true;
     else if (Property->getName() == "IntrHasSideEffects")
diff --git a/llvm/utils/TableGen/IntrinsicEmitter.cpp b/llvm/utils/TableGen/IntrinsicEmitter.cpp
index 06e44e3b57c..049282e5ebf 100644
--- a/llvm/utils/TableGen/IntrinsicEmitter.cpp
+++ b/llvm/utils/TableGen/IntrinsicEmitter.cpp
@@ -489,6 +489,9 @@ struct AttributeComparator {
     if (L->isNoReturn != R->isNoReturn)
       return R->isNoReturn;
 
+    if (L->isCold != R->isCold)
+      return R->isCold;
+
     if (L->isConvergent != R->isConvergent)
       return R->isConvergent;
 
@@ -622,7 +625,7 @@ void IntrinsicEmitter::EmitAttributes(const CodeGenIntrinsicTable &Ints,
 
     if (!intrinsic.canThrow ||
         intrinsic.ModRef != CodeGenIntrinsic::ReadWriteMem ||
-        intrinsic.isNoReturn || intrinsic.isNoDuplicate ||
+        intrinsic.isNoReturn || intrinsic.isCold || intrinsic.isNoDuplicate ||
         intrinsic.isConvergent || intrinsic.isSpeculatable) {
       OS << "      const Attribute::AttrKind Atts[] = {";
       bool addComma = false;
@@ -636,6 +639,12 @@ void IntrinsicEmitter::EmitAttributes(const CodeGenIntrinsicTable &Ints,
         OS << "Attribute::NoReturn";
         addComma = true;
       }
+      if (intrinsic.isCold) {
+        if (addComma)
+          OS << ",";
+        OS << "Attribute::Cold";
+        addComma = true;
+      }
       if (intrinsic.isNoDuplicate) {
         if (addComma)
           OS << ",";