[llvm-commits] [llvm] r143600 - in /llvm/trunk: lib/CodeGen/MachineInstr.cpp test/CodeGen/X86/MachineLICM-HoistSelectorRefs.ll

[Chris Lattner]

On Nov 2, 2011, at 5:56 PM, Pete Cooper wrote:

> Author: pete
> Date: Wed Nov  2 19:56:36 2011
> New Revision: 143600
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=143600&view=rev
> Log:
> Treat objc selector reference globals as invariant so that MachineLICM can hoist them out of loops.  Fixes <rdar://problem/6027699>

Hi Pete,

Special casing this by-name seems really gross.  Shouldn't this be handled by introducing a new linkage type, or some sort of metadata?  Also, would it be possible to catch this in the early LICM pass?

-Chris

>    llvm/trunk/test/CodeGen/X86/MachineLICM-HoistSelectorRefs.ll
> Modified:
>    llvm/trunk/lib/CodeGen/MachineInstr.cpp
> 
> Modified: llvm/trunk/lib/CodeGen/MachineInstr.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineInstr.cpp?rev=143600&r1=143599&r2=143600&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/MachineInstr.cpp (original)
> +++ llvm/trunk/lib/CodeGen/MachineInstr.cpp Wed Nov  2 19:56:36 2011
> @@ -1232,6 +1232,19 @@
>   return false;
> }
> 
> +/// pointsToRuntimeConstantMemory - Return true if this value points to data
> +/// which does never changes once the program starts running
> +static bool pointsToRuntimeConstantMemory(const Value *V) {
> +  if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) {
> +    StringRef Name = GV->getName();
> +    // These special values are known to be constant at runtime
> +    // TODO: a new linkage type for these would be far better than this check
> +    if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_"))
> +      return true;
> +  }
> +  return false;
> +}
> +
> /// isInvariantLoad - Return true if this instruction is loading from a
> /// location whose value is invariant across the function.  For example,
> /// loading a value from the constant pool or from the argument area
> @@ -1259,6 +1272,8 @@
>       if (const PseudoSourceValue *PSV = dyn_cast<PseudoSourceValue>(V))
>         if (PSV->isConstant(MFI))
>           continue;
> +      if (pointsToRuntimeConstantMemory(V))
> +        continue;
>       // If we have an AliasAnalysis, ask it whether the memory is constant.
>       if (AA && AA->pointsToConstantMemory(
>                       AliasAnalysis::Location(V, (*I)->getSize(),
> 
> Added: llvm/trunk/test/CodeGen/X86/MachineLICM-HoistSelectorRefs.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/MachineLICM-HoistSelectorRefs.ll?rev=143600&view=auto
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/MachineLICM-HoistSelectorRefs.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/MachineLICM-HoistSelectorRefs.ll Wed Nov  2 19:56:36 2011
> @@ -0,0 +1,30 @@
> +; RUN: llc < %s -march=x86-64 -mattr=+sse3,+sse41 -stats |& grep {1 machine-licm}
> +; rdar://6027699
> +
> +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
> +target triple = "x86_64-apple-macosx10.7.2"
> +
> +; STATS: 1 machine-licm
> +
> +@"\01L_OBJC_METH_VAR_NAME_" = internal global [4 x i8] c"foo\00", section "__TEXT,__objc_methname,cstring_literals", align 1
> +@"\01L_OBJC_SELECTOR_REFERENCES_" = internal global i8* getelementptr inbounds ([4 x i8]* @"\01L_OBJC_METH_VAR_NAME_", i64 0, i64 0), section "__DATA, __objc_selrefs, literal_pointers, no_dead_strip"
> +@"\01L_OBJC_IMAGE_INFO" = internal constant [2 x i32] [i32 0, i32 16], section "__DATA, __objc_imageinfo, regular, no_dead_strip"
> + at llvm.used = appending global [3 x i8*] [i8* getelementptr inbounds ([4 x i8]* @"\01L_OBJC_METH_VAR_NAME_", i32 0, i32 0), i8* bitcast (i8** @"\01L_OBJC_SELECTOR_REFERENCES_" to i8*), i8* bitcast ([2 x i32]* @"\01L_OBJC_IMAGE_INFO" to i8*)], section "llvm.metadata"
> +
> +define void @test(i8* %x) uwtable ssp {
> +entry:
> +  br label %for.body
> +
> +for.body:                                         ; preds = %for.body, %entry
> +  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
> +  %0 = load i8** @"\01L_OBJC_SELECTOR_REFERENCES_", align 8
> +  %call = tail call i8* bitcast (i8* (i8*, i8*, ...)* @objc_msgSend to i8* (i8*, i8*)*)(i8* %x, i8* %0)
> +  %inc = add i32 %i.01, 1
> +  %exitcond = icmp eq i32 %inc, 10000
> +  br i1 %exitcond, label %for.end, label %for.body
> +
> +for.end:                                          ; preds = %for.body
> +  ret void
> +}
> +
> +declare i8* @objc_msgSend(i8*, i8*, ...) nonlazybind
> 
> 
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