[InferAttrs] Mark frexp and modf as memory(argmem: write)

[dwoodwor-intel]

Summary

These two math library functions can't write to errno, but they do
produce two results and store the second result to a pointer passed as
their second argument. Appropriately marking them as
memory(argmem: write) enables more optimizations on calls to them.

[dwoodwor-intel]

I don't have commit access; @xbolva00, can you merge this for me? Please use Daniel Woodworth <[e-mail]> as my name/email address

[dwoodwor-intel]

It's been a week, so it's time for a review ping.

@xbolva00, does this change needs more approvals? Should I nominate someone else to merge it?

[xbolva00]

Yes, please, as I would be able to commit it for you only next week.

[vitalybuka]

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

481–482

this is not true with sanitizers, interceptors may check metadata

Maybe we can add TargetLibraryInfo::hasSanitizer() and use it here

[efriedma]

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

481–482

If this is actually an issue, it would impact every libcall we mark with memory attributes; please move the discussion elsewhere (maybe a Discourse thread).

llvm/lib/Transforms/Utils/BuildLibCalls.cpp

case LibFunc_memrchr:
     Changed |= setOnlyReadsMemory(F);
     Changed |= setWillReturn(F);
     break;
   case LibFunc_modf:
   case LibFunc_modff:
   case LibFunc_modfl:
     Changed |= setDoesNotThrow(F);
     Changed |= setWillReturn(F);
+    Changed |= setOnlyAccessesArgMemory(F);
+    Changed |= setOnlyWritesMemory(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_memcpy:
     Changed |= setDoesNotThrow(F);
     Changed |= setOnlyAccessesArgMemory(F);
     Changed |= setWillReturn(F);
     Changed |= setDoesNotAlias(F, 0);
     Changed |= setReturnedArg(F, 0);
case LibFunc_fstat:
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_frexp:
   case LibFunc_frexpf:
   case LibFunc_frexpl:
     Changed |= setDoesNotThrow(F);
     Changed |= setWillReturn(F);
+    Changed |= setOnlyAccessesArgMemory(F);
+    Changed |= setOnlyWritesMemory(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_fstatvfs:
     Changed |= setRetAndArgsNoUndef(F);
     Changed |= setDoesNotThrow(F);
     Changed |= setDoesNotCapture(F, 1);
     break;
   case LibFunc_fgets:

llvm/test/Transforms/InferFunctionAttrs/annotate.ll

 declare i64 @fread(ptr, i64, i64, ptr)
 
 ; CHECK: declare void @free(ptr allocptr nocapture noundef) [[INACCESSIBLEMEMORARGMEMONLY_NOUNWIND_WILLRETURN_ALLOCKIND_FREE_FAMILY_MALLOC:#[0-9]+]]
 declare void @free(ptr)
 
 ; CHECK-AIX: declare void @vec_free(ptr allocptr nocapture noundef) [[INACCESSIBLEMEMORARGMEMONLY_NOUNWIND_WILLRETURN_FAMILY_VEC_MALLOC:#[0-9]+]]
 declare void @vec_free(ptr)
 
-; CHECK: declare double @frexp(double, ptr nocapture) [[NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
+; CHECK: declare double @frexp(double, ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN_WRITEONLY:#[0-9]+]]
 declare double @frexp(double, ptr)
 
-; CHECK: declare float @frexpf(float, ptr nocapture) [[NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare float @frexpf(float, ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare float @frexpf(float, ptr)
 
-; CHECK: declare x86_fp80 @frexpl(x86_fp80, ptr nocapture) [[NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare x86_fp80 @frexpl(x86_fp80, ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare x86_fp80 @frexpl(x86_fp80, ptr)
 
 ; CHECK: declare noundef i32 @fscanf(ptr nocapture noundef, ptr nocapture noundef readonly, ...) [[NOFREE_NOUNWIND]]
 declare i32 @fscanf(ptr, ptr, ...)
 
 ; CHECK: declare noundef i32 @fseek(ptr nocapture noundef, i64 noundef, i32 noundef) [[NOFREE_NOUNWIND]]
 declare i32 @fseek(ptr, i64, i32)
 

 declare ptr @memset(ptr, i32, i64)
 
 ; CHECK: declare ptr @__memset_chk(ptr writeonly, i32, i64, i64) [[ARGMEMONLY_NOFREE_NOUNWIND]]
 declare ptr @__memset_chk(ptr, i32, i64, i64)
 
 ; CHECK: declare noundef i32 @mkdir(ptr nocapture noundef readonly, i16 noundef zeroext) [[NOFREE_NOUNWIND]]
 declare i32 @mkdir(ptr, i16 zeroext)
 
-; CHECK: declare noundef i64 @mktime(ptr nocapture noundef) [[NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare noundef i64 @mktime(ptr nocapture noundef) [[NOFREE_NOUNWIND_WILLRETURN:#[0-9]+]]
 declare i64 @mktime(ptr)
 
-; CHECK: declare double @modf(double, ptr nocapture) [[NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare double @modf(double, ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare double @modf(double, ptr)
 
-; CHECK: declare float @modff(float, ptr nocapture) [[NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare float @modff(float, ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare float @modff(float, ptr)
 
-; CHECK: declare x86_fp80 @modfl(x86_fp80, ptr nocapture) [[NOFREE_NOUNWIND_WILLRETURN]]
+; CHECK: declare x86_fp80 @modfl(x86_fp80, ptr nocapture) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare x86_fp80 @modfl(x86_fp80, ptr)
 
 ; CHECK: declare double @nearbyint(double) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare double @nearbyint(double)
 
 ; CHECK: declare float @nearbyintf(float) [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]]
 declare float @nearbyintf(float)
 

 declare void @memset_pattern4(ptr, ptr, i64)
 ; CHECK-DARWIN: declare void @memset_pattern8(ptr nocapture writeonly, ptr nocapture readonly, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
 declare void @memset_pattern8(ptr, ptr, i64)
 ; CHECK-DARWIN: declare void @memset_pattern16(ptr nocapture writeonly, ptr nocapture readonly, i64) [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]]
 declare void @memset_pattern16(ptr, ptr, i64)
 
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND_WILLRETURN]] = { mustprogress nofree nounwind willreturn }
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]] = { mustprogress nofree nounwind willreturn memory(write) }
+; CHECK-DAG: attributes [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN_WRITEONLY]] = { mustprogress nofree nounwind willreturn memory(argmem: write) }
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND]] = { nofree nounwind }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN_ALLOCKIND_ALLOCUNINIT_ALLOCSIZE1_FAMILY_MALLOC]] = { mustprogress nofree nounwind willreturn allockind("alloc,uninitialized,aligned") allocsize(1) memory(inaccessiblemem: readwrite) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMONLY_NOFREE_NOUNWIND_WILLRETURN_ALLOCKIND_ALLOCZEROED_ALLOCSIZE01_FAMILY_MALLOC]] = { mustprogress nofree nounwind willreturn allockind("alloc,zeroed") allocsize(0,1) memory(inaccessiblemem: readwrite) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND_READONLY_WILLRETURN]] = { mustprogress nofree nounwind willreturn memory(read) }
 ; CHECK-DAG: attributes [[ARGMEMONLY_NOFREE_NOUNWIND_WILLRETURN]] = { mustprogress nofree nounwind willreturn memory(argmem: readwrite) }
 ; CHECK-DAG: attributes [[NOFREE_NOUNWIND_READONLY]] = { nofree nounwind memory(read) }
 ; CHECK-DAG: attributes [[INACCESSIBLEMEMORARGMEMONLY_NOUNWIND_WILLRETURN_ALLOCKIND_FREE_FAMILY_MALLOC]] = { mustprogress nounwind willreturn allockind("free") memory(argmem: readwrite, inaccessiblemem: readwrite) "alloc-family"="malloc" }
 ; CHECK-DAG: attributes [[NOFREE_WILLRETURN]] = { mustprogress nofree willreturn }