[LibCalls] Mark puts/printf/perror as inaccessible_mem_or_argmem.

[fhahn]

Summary

Unless I am missing something, those functions should only access
either memory accessible through their arguments or inaccessible memory.

If I am not missing anything, it would probably be worth to add that
attribute to most libcalls.

[efriedma]

They can also write to errno.

[fhahn]

In D132406#3740566, @efriedma wrote:

They can also write to errno.

Argh, right, that's a shame. I think the most interesting property would be that they don't access local objects that have been captured. But I think we don't have a way to model that at the moment?

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

case LibFunc_putc_unlocked:
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_puts:
   case LibFunc_printf:
   case LibFunc_perror:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 0);
+    Changed |= setOnlyAccessesInaccessibleMemOrArgMem(F);
     Changed |= setOnlyReadsMemory(F, 0);
     break;
   case LibFunc_pread:
     // May throw; "pread" is a valid pthread cancellation point.
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_pwrite:

llvm/test/Transforms/InferFunctionAttrs/annotate.ll

 ; CHECK-LINUX: declare noundef i32 @open64(i8* nocapture noundef readonly, i32 noundef, ...) [[NOFREE]]
 declare i32 @open64(i8*, i32, ...)
 
 ; CHECK: declare noalias noundef %opaque* @opendir(i8* nocapture noundef readonly) [[NOFREE_NOUNWIND]]
 declare %opaque* @opendir(i8*)
 
 ; CHECK: declare noundef i32 @pclose(%opaque* nocapture noundef) [[NOFREE_NOUNWIND]]
 declare i32 @pclose(%opaque*)
-
-; CHECK: declare void @perror(i8* nocapture noundef readonly) [[NOFREE_NOUNWIND]]
+; CHECK: declare void @perror(i8* nocapture noundef readonly) [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND:#[0-9]+]]
 declare void @perror(i8*)
 
 ; CHECK: declare noalias noundef %opaque* @popen(i8* nocapture noundef readonly, i8* nocapture noundef readonly) [[NOFREE_NOUNWIND]]
 declare %opaque* @popen(i8*, i8*)
 
 ; CHECK: declare i32 @posix_memalign(i8**, i64, i64) [[NOFREE]]
 declare i32 @posix_memalign(i8**, i64, i64)
 
 ; CHECK: declare double @pow(double, double) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare double @pow(double, double)
 
 ; CHECK: declare float @powf(float, float) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare float @powf(float, float)
 
 ; CHECK: declare x86_fp80 @powl(x86_fp80, x86_fp80) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare x86_fp80 @powl(x86_fp80, x86_fp80)
 
 ; CHECK: declare noundef i64 @pread(i32 noundef, i8* nocapture noundef, i64 noundef, i64 noundef) [[NOFREE]]
 declare i64 @pread(i32, i8*, i64, i64)
 
-; CHECK: declare noundef i32 @printf(i8* nocapture noundef readonly, ...) [[NOFREE_NOUNWIND]]
+; CHECK: declare noundef i32 @printf(i8* nocapture noundef readonly, ...) [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND]]
 declare i32 @printf(i8*, ...)
 
 ; CHECK: declare noundef i32 @putc(i32 noundef, %opaque* nocapture noundef) [[NOFREE_NOUNWIND]]
 declare i32 @putc(i32, %opaque*)
 
 ; CHECK: declare noundef i32 @putchar(i32 noundef) [[NOFREE_NOUNWIND]]
 declare i32 @putchar(i32)
 
 ; CHECK-KNOWN: declare noundef i32 @putchar_unlocked(i32 noundef) [[NOFREE_NOUNWIND]]
 ; CHECK-UNKNOWN: declare i32 @putchar_unlocked(i32){{$}}
 declare i32 @putchar_unlocked(i32)
 
-; CHECK: declare noundef i32 @puts(i8* nocapture noundef readonly) [[NOFREE_NOUNWIND]]
+; CHECK: declare noundef i32 @puts(i8* nocapture noundef readonly) [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND]]
 declare i32 @puts(i8*)
 
 ; CHECK: declare noundef i64 @pwrite(i32 noundef, i8* nocapture noundef readonly, i64 noundef, i64 noundef) [[NOFREE]]
 declare i64 @pwrite(i32, i8*, i64, i64)
 
 ; CHECK: declare void @qsort(i8* noundef, i64 noundef, i64 noundef, i32 (i8*, i8*)* nocapture noundef) [[NOFREE]]
 declare void @qsort(i8*, i64, i64, i32 (i8*, i8*)*)
 

 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGMEMONLY_NOUNWIND_WILLRETURN_ALLOCKIND_FREE_FAMILY_MALLOC]] = { inaccessiblemem_or_argmemonly mustprogress nounwind willreturn allockind("free") "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[NOFREE_WILLRETURN]] = { mustprogress nofree willreturn }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN_ALLOCKIND_ALLOCUNINIT_ALLOCSIZE0_FAMILY_MALLOC]] = { inaccessiblememonly mustprogress nofree nounwind willreturn allockind("alloc,uninitialized") allocsize(0) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[ARGMEMONLY_NOFREE_NOUNWIND_READONLY_WILLRETURN]] = { argmemonly mustprogress nofree nounwind readonly willreturn }
 ; CHECK-DAG: attributes [[NOFREE]] = { nofree }
 ; CHECK-DAG: attributes [[ARGMEMONLY_NOFREE_NOUNWIND]] = { argmemonly nofree nounwind }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGMEMONLY_NOUNWIND_WILLRETURN_ALLOCKIND_REALLOC_ALLOCSIZE1_FAMILY_MALLOC]] = { inaccessiblemem_or_argmemonly mustprogress nounwind willreturn allockind("realloc") allocsize(1) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND_WILLRETURN_FAMILY_MALLOC]] = { inaccessiblemem_or_argmemonly mustprogress nofree nounwind willreturn "alloc-family"="malloc" }
+; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGONLY_NOFREE_NOUNWIND]] = { inaccessiblemem_or_argmemonly nofree nounwind }
 
 ; CHECK-NVPTX-DAG: attributes [[NOFREE_NOUNWIND_READNONE]] = { nofree nosync nounwind readnone }
 
 ; CHECK-AIX-DAG: attributes [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN_ALLOCSIZE0_FAMILY_VEC_MALLOC]] = { inaccessiblememonly mustprogress nofree nounwind willreturn allockind("alloc,uninitialized") allocsize(0) "alloc-family"="vec_malloc" }
 ; CHECK-AIX-DAG: attributes [[INACCESSIBLEMEMORARGMEMONLY_NOUNWIND_WILLRETURN_FAMILY_VEC_MALLOC]] = { inaccessiblemem_or_argmemonly mustprogress nounwind willreturn allockind("free") "alloc-family"="vec_malloc" }
 ; CHECK-AIX-DAG: attributes [[INACCESSIBLEMEMORARGMEMONLY_NOUNWIND_WILLRETURN_ALLOCSIZE_FAMILY_VEC_MALLOC]] = { inaccessiblemem_or_argmemonly mustprogress nounwind willreturn allockind("realloc") allocsize(1) "alloc-family"="vec_malloc" }
 ; CHECK-AIX-DAG: attributes [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN_ALLOCSIZE01_FAMILY_VEC_MALLOC]] = { inaccessiblememonly mustprogress nofree nounwind willreturn allockind("alloc,zeroed") allocsize(0,1) "alloc-family"="vec_malloc" }