From 378ab7ce3d627cdb1b44ac61220079113df57192 Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Wed, 8 Jul 2015 03:59:31 +0000
Subject: [PATCH] ARM: force on +vfp2 (ref #11817, ref #10602)

this seems likely to be a better default for the majority of users. plus the failure mode is a SIGILL, rather than random data getting returned from floating point computations
---
 README.arm.md   | 11 +++++++----
 src/codegen.cpp | 16 +++++++++++-----
 2 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/README.arm.md b/README.arm.md
index ea30b115f8784..97096189dbff0 100644
--- a/README.arm.md
+++ b/README.arm.md
@@ -57,10 +57,9 @@ If you run into issues building LLVM, see these notes:
 
 # Raspberry Pi
 
-The Raspberry Pi ARM CPU is not correctly detected by LLVM. Before
-starting the build, `export JULIA_CPU_ARCH=arm1176jzf-s`. This tells
-LLVM that the CPU has VFP support. See the discussion in
-[#10917](https://github.com/JuliaLang/julia/issues/10917).
+The Raspberry Pi ARM CPU type is not detected by LLVM.
+Before starting the build, it is recommented to add `export JULIA_CPU_ARCH=arm1176jzf-s`
+to your Make.user file to tune the generated code for your CPU architecture.
 
 # Raspberry Pi 2
 
@@ -73,6 +72,10 @@ In the case of Raspberry Pi 2, download LLVM binaries from the LLVM website, sin
 override USE_SYSTEM_LLVM=1
 ```
 
+# SIGILL during sysimg.o creation
+
+Its likely that your cpu does not support VFP. File an issue on the Julia issue tracker with the contents of /proc/cpuinfo.
+
 
 # Chromebook
 
diff --git a/src/codegen.cpp b/src/codegen.cpp
index 5605542e9fcd3..1e833c6fb0c95 100644
--- a/src/codegen.cpp
+++ b/src/codegen.cpp
@@ -5604,6 +5604,7 @@ extern "C" void jl_init_codegen(void)
     jl_mcjmm = new SectionMemoryManager();
 #endif
     const char *mattr[] = {
+#if defined(_CPU_X86_64_) || defined(_CPU_X86_)
 #ifndef USE_MCJIT
         // Temporarily disable Haswell BMI2 features due to LLVM bug.
         "-bmi2", "-avx2",
@@ -5611,6 +5612,8 @@ extern "C" void jl_init_codegen(void)
 #ifdef V128_BUG
         "-avx",
 #endif
+#endif
+        "", // padding to make sure this isn't an empty array (ref #11817)
     };
     SmallVector<std::string, 4> MAttrs(mattr, mattr+sizeof(mattr)/sizeof(mattr[0]));
 #ifdef LLVM36
@@ -5640,14 +5643,17 @@ extern "C" void jl_init_codegen(void)
     TheTriple.setEnvironment(Triple::ELF);
 #endif
 #endif
+   StringRef TheCPU = strcmp(jl_options.cpu_target,"native") ? StringRef(jl_options.cpu_target) : StringRef(sys::getHostCPUName());
+    if (TheCPU.empty() || TheCPU == StringRef("generic")) {
+        jl_printf(JL_STDERR, "warning: unable to determine host cpu name.\n");
+#ifdef _CPU_ARM_
+        MAttrs.append(1, "+vfp2"); // the processors that don't have VFP are old and (hopefully) rare. this affects the platform calling convention.
+#endif
+    }
     TargetMachine *targetMachine = eb.selectTarget(
             TheTriple,
             "",
-#if LLVM35
-            strcmp(jl_options.cpu_target,"native") ? StringRef(jl_options.cpu_target) : sys::getHostCPUName(),
-#else
-            strcmp(jl_options.cpu_target,"native") ? jl_options.cpu_target : "",
-#endif
+            TheCPU,
             MAttrs);
     jl_TargetMachine = targetMachine->getTarget().createTargetMachine(
             TheTriple.getTriple(),