From 573f3f8d487dfd1f56ab71b96ad23af1a2d4162e Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Mon, 6 Feb 2017 13:50:19 -0500
Subject: [PATCH] coldcc works better

 * Only use Cold Calling Convention on x86
 * Add the cold attribute to functions marked with coldcc
---
 src/analyze.cpp  | 12 +++++++-----
 src/codegen.cpp  |  3 +++
 src/zig_llvm.cpp |  8 ++++++++
 src/zig_llvm.hpp |  1 +
 4 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/src/analyze.cpp b/src/analyze.cpp
index 23040f2dd7..df554b6727 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -713,12 +713,14 @@ TypeTableEntry *get_fn_type(CodeGen *g, FnTypeId *fn_type_id) {
     fn_type->data.fn.fn_type_id = *fn_type_id;
 
     if (fn_type_id->is_cold) {
-        if (g->zig_target.arch.arch == ZigLLVM_arm) {
-            // TODO we want to use coldcc here but it's causing a segfault on ARM
-            // https://llvm.org/bugs/show_bug.cgi?id=31875
-            fn_type->data.fn.calling_convention = LLVMCCallConv;
-        } else {
+        // cold calling convention only works on x86.
+        // but we can add the cold attribute later.
+        if (g->zig_target.arch.arch == ZigLLVM_x86 ||
+            g->zig_target.arch.arch == ZigLLVM_x86_64)
+        {
             fn_type->data.fn.calling_convention = LLVMColdCallConv;
+        } else {
+            fn_type->data.fn.calling_convention = LLVMFastCallConv;
         }
     } else if (fn_type_id->is_extern) {
         fn_type->data.fn.calling_convention = LLVMCCallConv;
diff --git a/src/codegen.cpp b/src/codegen.cpp
index 7383cf8769..292aa22566 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -268,6 +268,9 @@ static LLVMValueRef fn_llvm_value(CodeGen *g, FnTableEntry *fn_table_entry) {
         LLVMAddFunctionAttr(fn_table_entry->llvm_value, LLVMNoReturnAttribute);
     }
     LLVMSetFunctionCallConv(fn_table_entry->llvm_value, fn_type->data.fn.calling_convention);
+    if (fn_type->data.fn.fn_type_id.is_cold) {
+        ZigLLVMAddFunctionAttrCold(fn_table_entry->llvm_value);
+    }
     LLVMAddFunctionAttr(fn_table_entry->llvm_value, LLVMNoUnwindAttribute);
     if (!g->is_release_build && fn_table_entry->fn_inline != FnInlineAlways) {
         ZigLLVMAddFunctionAttr(fn_table_entry->llvm_value, "no-frame-pointer-elim", "true");
diff --git a/src/zig_llvm.cpp b/src/zig_llvm.cpp
index d6c32b01b2..c59a533a05 100644
--- a/src/zig_llvm.cpp
+++ b/src/zig_llvm.cpp
@@ -561,6 +561,14 @@ void ZigLLVMAddFunctionAttr(LLVMValueRef fn_ref, const char *attr_name, const ch
     func->setAttributes(new_attr_set);
 }
 
+void ZigLLVMAddFunctionAttrCold(LLVMValueRef fn_ref) {
+    Function *func = unwrap<Function>(fn_ref);
+    const AttributeSet attr_set = func->getAttributes();
+    const AttributeSet new_attr_set = attr_set.addAttribute(func->getContext(), AttributeSet::FunctionIndex,
+            Attribute::Cold);
+    func->setAttributes(new_attr_set);
+}
+
 
 static_assert((Triple::ArchType)ZigLLVM_LastArchType == Triple::LastArchType, "");
 static_assert((Triple::VendorType)ZigLLVM_LastVendorType == Triple::LastVendorType, "");
diff --git a/src/zig_llvm.hpp b/src/zig_llvm.hpp
index d6795db68c..0062757b95 100644
--- a/src/zig_llvm.hpp
+++ b/src/zig_llvm.hpp
@@ -165,6 +165,7 @@ ZigLLVMDILocation *ZigLLVMGetDebugLoc(unsigned line, unsigned col, ZigLLVMDIScop
 void ZigLLVMSetFastMath(LLVMBuilderRef builder_wrapped, bool on_state);
 
 void ZigLLVMAddFunctionAttr(LLVMValueRef fn, const char *attr_name, const char *attr_value);
+void ZigLLVMAddFunctionAttrCold(LLVMValueRef fn);
 
 unsigned ZigLLVMGetPrefTypeAlignment(LLVMTargetDataRef TD, LLVMTypeRef Ty);