Attach attribute "trap-func-name" to IR function

[ahatanak]

Summary

This patch is part of the work to make LTO and function multi-versioning work correctly.

Currently, the trap function name users specify on the command line using -ftrap-function is passed to the backend via TargetMachine's TargetOptions. This patch attaches attribute "trap-func-name" to the IR function instead so that we can use -ftrap-function for LTO builds and change the trap function name on a per-function basis.

[echristo]

Not sure we necessarily need a "put these function attributes on the functions" command line and map? Rationale?

-eric

[ahatanak]

In D10831#196951, @echristo wrote:

Not sure we necessarily need a "put these function attributes on the functions" command line and map? Rationale?

That's a good point. I don't think we need a new cc1 option for trap-function at all.

[ahatanak]

Remove cc1 option and simplify patch.

[echristo]

Lgtm thanks.

[ahatanak]

Thanks, I'll send the corresponding llvm patch shortly.

[ahatanak]

The new patch attaches "trap-func-name" to the call sites instead of the calling functions, which simplifies the handling of the attribute when functions are merged and inlined.

The relevant discussion I had with Eric is here:
http://reviews.llvm.org/D10832

[echristo]

You'll want to also test a trap inside of a ctor/dtor, global constructor (if you can), etc. The general change looks fine though.

Thanks!

-eric

[ahatanak]

I wasn't sure how to test traps inside ctor/dtor or global constructor, so I went ahead and committed the reviewed patch. I can add the tests later if I can find a way to emit traps for those functions.

[pcc]

Maybe I'm missing something, but I don't see why we need this attribute. Couldn't clang have been changed to implement -ftrap-function by generating a call to the trap function instead of emitting an llvm.trap intrinsic call?

[ahatanak]

AMDGPUAnnotateKernelFeatures::addFeatureAttributes looks for an llvm.trap instruction and adds attribute "amdgpu-queue-ptr" to the function if it finds one.

Other than that, it looks like your idea would work too.

lib/CodeGen/BackendUtil.cpp

TargetMachine *EmitAssemblyHelper::CreateTargetMachine(bool MustCreateTM) {
   }
 
   Options.LessPreciseFPMADOption = CodeGenOpts.LessPreciseFPMAD;
   Options.NoInfsFPMath = CodeGenOpts.NoInfsFPMath;
   Options.NoNaNsFPMath = CodeGenOpts.NoNaNsFPMath;
   Options.NoZerosInBSS = CodeGenOpts.NoZeroInitializedInBSS;
   Options.UnsafeFPMath = CodeGenOpts.UnsafeFPMath;
   Options.StackAlignmentOverride = CodeGenOpts.StackAlignment;
-  Options.TrapFuncName = CodeGenOpts.TrapFuncName;
   Options.PositionIndependentExecutable = LangOpts.PIELevel != 0;
   Options.FunctionSections = CodeGenOpts.FunctionSections;
   Options.DataSections = CodeGenOpts.DataSections;
   Options.UniqueSectionNames = CodeGenOpts.UniqueSectionNames;
 
   Options.MCOptions.MCRelaxAll = CodeGenOpts.RelaxAll;
   Options.MCOptions.MCSaveTempLabels = CodeGenOpts.SaveTempLabels;
   Options.MCOptions.MCUseDwarfDirectory = !CodeGenOpts.NoDwarfDirectoryAsm;

lib/CodeGen/CGCall.cpp

if (AttrOnCallSite) {
     FuncAttrs.addAttribute("use-soft-float",
                            llvm::toStringRef(CodeGenOpts.SoftFloat));
     FuncAttrs.addAttribute("stack-protector-buffer-size",
                            llvm::utostr(CodeGenOpts.SSPBufferSize));
 
     if (!CodeGenOpts.StackRealignment)
       FuncAttrs.addAttribute("no-realign-stack");
 
+    if (!CodeGenOpts.TrapFuncName.empty())
+      FuncAttrs.addAttribute("trap-func-name", CodeGenOpts.TrapFuncName);
+
     // Add target-cpu and target-features attributes to functions. If
     // we have a decl for the function and it has a target attribute then
     // parse that and add it to the feature set.
     StringRef TargetCPU = getTarget().getTargetOpts().CPU;
 
     // TODO: Features gets us the features on the command line including
     // feature dependencies. For canonicalization purposes we might want to
     // avoid putting features in the target-features set if we know it'll be

test/CodeGen/fn-attr.c

+// RUN: %clang_cc1 -triple thumbv7-apple-ios5 -function-attribute trap-func-name=trapfuncname1 -emit-llvm -o - %s | FileCheck %s
+
+// CHECK: attributes #0 = { {{.*}} "trap-func-name"="trapfuncname1"
+
+int foo1(int a) { return a; }