[llvm-dev] How to add NOP?

[Volkan Keles via llvm-dev]

According to LLVM Language Reference Manual (
http://llvm.org/docs/LangRef.html#global-variables), the address space is 0
for those global variables.

"A global variable may be declared to reside in a target-specific numbered
address space. For targets that support them, address spaces may affect how
optimizations are performed and/or what target instructions are used to
access the variable. The default address space is zero. The address space
qualifier must precede any other attributes."

Volkan


On Mon, Oct 12, 2015 at 5:31 AM Erdem Derebaşoğlu <
erdemderebasoglu at hotmail.com> wrote:

> Here it is:
>
> ; ModuleID = 'omp_hello.c'
> target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
> target triple = "x86_64-unknown-linux-gnu"
>
> %ident_t = type { i32, i32, i32, i32, i8* }
> %struct.anon = type { i32* }
>
> @.str = private unnamed_addr constant [30 x i8] c"Hello World from thread
> = %d\0A\00", align 1
> @.str.1 = private unnamed_addr constant [24 x i8] c"Number of threads =
> %d\0A\00", align 1
> @.str.2 = private unnamed_addr constant [23 x i8]
> c";unknown;unknown;0;0;;\00", align 1
> @0 = private unnamed_addr constant %ident_t { i32 0, i32 66, i32 0, i32 0,
> i8* getelementptr inbounds ([23 x i8], [23 x i8]* @.str.2, i32 0, i32 0) }
> @1 = private unnamed_addr constant %ident_t { i32 0, i32 2, i32 0, i32 0,
> i8* getelementptr inbounds ([23 x i8], [23 x i8]* @.str.2, i32 0, i32 0) }
>
> ; Function Attrs: nounwind optsize uwtable
> define i32 @main(i32 %argc, i8** nocapture readnone %argv) #0 {
> entry:
>   %a = alloca i32, align 4
>   %agg.captured = alloca %struct.anon, align 8
>   tail call void @omp_set_num_threads(i32 4) #4
>   %0 = bitcast i32* %a to i8*
>   call void @llvm.lifetime.start(i64 4, i8* %0) #1
>   store i32 5, i32* %a, align 4, !tbaa !1
>   %1 = getelementptr inbounds %struct.anon, %struct.anon* %agg.captured,
> i64 0, i32 0
>   store i32* %a, i32** %1, align 8, !tbaa !5
>   call void (%ident_t*, i32, void (i32*, i32*, ...)*, ...)
> @__kmpc_fork_call(%ident_t* nonnull @1, i32 1, void (i32*, i32*, ...)*
> bitcast (void (i32*, i32*, %struct.anon*)* @.omp_outlined. to void (i32*,
> i32*, ...)*), %struct.anon* nonnull %agg.captured) #1
>   call void @llvm.lifetime.end(i64 4, i8* %0) #1
>   ret i32 0
> }
>
> ; Function Attrs: nounwind
> declare void @llvm.lifetime.start(i64, i8* nocapture) #1
>
> ; Function Attrs: optsize
> declare void @omp_set_num_threads(i32) #2
>
> ; Function Attrs: nounwind optsize uwtable
> define internal void @.omp_outlined.(i32* nocapture readonly
> %.global_tid., i32* nocapture readnone %.bound_tid., %struct.anon*
> nocapture readonly %__context) #0 {
> entry:
>   %call = tail call i32 @omp_get_thread_num() #4
>   %0 = getelementptr inbounds %struct.anon, %struct.anon* %__context, i64
> 0, i32 0
>   %ref = load i32*, i32** %0, align 8, !tbaa !5
>   %1 = load i32, i32* %ref, align 4, !tbaa !1
>   %call1 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds
> ([30 x i8], [30 x i8]* @.str, i64 0, i64 0), i32 %1) #4
>   %cmp = icmp eq i32 %call, 0
>   br i1 %cmp, label %if.then, label %if.end
>
> if.then:                                          ; preds = %entry
> call void asm "negl %eax;", ""()
>   %call2 = tail call i32 @omp_get_num_threads() #4
>   %call3 = tail call i32 (i8*, ...) @printf(i8* getelementptr inbounds
> ([24 x i8], [24 x i8]* @.str.1, i64 0, i64 0), i32 %call2) #4
>   br label %if.end
>
> if.end:                                           ; preds = %if.then,
> %entry
>   %2 = load i32, i32* %.global_tid., align 4, !tbaa !1
>   %3 = tail call i32 @__kmpc_cancel_barrier(%ident_t* nonnull @0, i32 %2)
> #1
>   ret void
> }
>
> ; Function Attrs: optsize
> declare i32 @omp_get_thread_num() #2
>
> ; Function Attrs: nounwind optsize
> declare i32 @printf(i8* nocapture readonly, ...) #3
>
> ; Function Attrs: optsize
> declare i32 @omp_get_num_threads() #2
>
> declare i32 @__kmpc_cancel_barrier(%ident_t*, i32)
>
> ; Function Attrs: nounwind
> declare void @llvm.lifetime.end(i64, i8* nocapture) #1
>
> declare void @__kmpc_fork_call(%ident_t*, i32, void (i32*, i32*, ...)*,
> ...)
>
> attributes #0 = { nounwind optsize uwtable "disable-tail-calls"="false"
> "less-precise-fpmad"="false" "no-frame-pointer-elim"="false"
> "no-infs-fp-math"="false" "no-nans-fp-math"="false"
> "stack-protector-buffer-size"="8" "target-cpu"="x86-64"
> "target-features"="+sse,+sse2" "unsafe-fp-math"="false"
> "use-soft-float"="false" }
> attributes #1 = { nounwind }
> attributes #2 = { optsize "disable-tail-calls"="false"
> "less-precise-fpmad"="false" "no-frame-pointer-elim"="false"
> "no-infs-fp-math"="false" "no-nans-fp-math"="false"
> "stack-protector-buffer-size"="8" "target-cpu"="x86-64"
> "target-features"="+sse,+sse2" "unsafe-fp-math"="false"
> "use-soft-float"="false" }
> attributes #3 = { nounwind optsize "disable-tail-calls"="false"
> "less-precise-fpmad"="false" "no-frame-pointer-elim"="false"
> "no-infs-fp-math"="false" "no-nans-fp-math"="false"
> "stack-protector-buffer-size"="8" "target-cpu"="x86-64"
> "target-features"="+sse,+sse2" "unsafe-fp-math"="false"
> "use-soft-float"="false" }
> attributes #4 = { nounwind optsize }
>
> !llvm.ident = !{!0}
>
> !0 = !{!"clang version 3.8.0 (trunk 243832)"}
> !1 = !{!2, !2, i64 0}
> !2 = !{!"int", !3, i64 0}
> !3 = !{!"omnipotent char", !4, i64 0}
> !4 = !{!"Simple C/C++ TBAA"}
> !5 = !{!3, !3, i64 0}
>
> Erdem
>
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