Skip to content

Commit

Permalink
[BuildLibCalls] Add more noundef to library functions
Browse files Browse the repository at this point in the history 
This patch follows D85345 and adds more noundef attributes to return values/arguments of library functions
that are mostly about accessing the file system or processes.

A few functions like `chmod` or `times` use typedef `mode_t` and `clock_t`.
They are neither struct nor union, so they cannot contain undef even if they're lowered to iN in IR. So, it is fine to add noundef to them.

- clock_t's actual type is size_t (C17, 7.27.1.3), so it isn't struct or union.

- For mode_t, either int or long is used in practice because programmers use bit manipulation. So, I think it is okay that it's never aggregate in practice.

After this patch, the remaining library functions are those that eagerly participate in optimizations: they can be removed, reordered, or
introduced by a transformation from primitive IR operations.
For them, a few testings is needed, since it may not be valid to add noundef anymore even if C standard says it's okay.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D85894
  • Loading branch information
@aqjune
aqjune committed Sep 9, 2020
1 parent 0fd425a commit 36c8621
Show file tree
Hide file tree
Showing 2 changed files with 75 additions and 42 deletions.
33 changes: 33 additions & 0 deletions llvm/lib/Transforms/Utils/BuildLibCalls.cpp
View file
Expand Up @@ -262,6 +262,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
return Changed;
case LibFunc_setbuf:
case LibFunc_setvbuf:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
return Changed;
Expand All @@ -274,6 +275,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
return Changed;
case LibFunc_stat:
case LibFunc_statvfs:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setDoesNotCapture(F, 1);
Expand Down Expand Up @@ -304,13 +306,15 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setOnlyReadsMemory(F, 2);
return Changed;
case LibFunc_setitimer:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 1);
Changed |= setDoesNotCapture(F, 2);
Changed |= setOnlyReadsMemory(F, 1);
return Changed;
case LibFunc_system:
// May throw; "system" is a valid pthread cancellation point.
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
Expand Down Expand Up @@ -369,11 +373,13 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setRetDoesNotAlias(F);
return Changed;
case LibFunc_mkdir:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_mktime:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
return Changed;
Expand All @@ -395,18 +401,21 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
case LibFunc_rmdir:
case LibFunc_remove:
case LibFunc_realpath:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_rename:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setDoesNotCapture(F, 1);
Changed |= setOnlyReadsMemory(F, 0);
Changed |= setOnlyReadsMemory(F, 1);
return Changed;
case LibFunc_readlink:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setDoesNotCapture(F, 1);
Expand Down Expand Up @@ -445,13 +454,15 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
return Changed;
case LibFunc_chmod:
case LibFunc_chown:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_ctermid:
case LibFunc_clearerr:
case LibFunc_closedir:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
return Changed;
Expand All @@ -464,6 +475,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotCapture(F, 0);
return Changed;
case LibFunc_access:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
Expand Down Expand Up @@ -583,6 +595,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotCapture(F, 0);
return Changed;
case LibFunc_getlogin_r:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
return Changed;
Expand All @@ -592,6 +605,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotCapture(F, 0);
return Changed;
case LibFunc_getenv:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setOnlyReadsMemory(F);
Changed |= setDoesNotCapture(F, 0);
Expand All @@ -603,10 +617,12 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotThrow(F);
return Changed;
case LibFunc_getitimer:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 1);
return Changed;
case LibFunc_getpwnam:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
Expand All @@ -617,21 +633,25 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotCapture(F, 1);
return Changed;
case LibFunc_uname:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
return Changed;
case LibFunc_unlink:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_unsetenv:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_utime:
case LibFunc_utimes:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setDoesNotCapture(F, 1);
Expand Down Expand Up @@ -669,6 +689,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotThrow(F);
return Changed;
case LibFunc_popen:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setRetDoesNotAlias(F);
Changed |= setDoesNotCapture(F, 0);
Expand All @@ -677,6 +698,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setOnlyReadsMemory(F, 1);
return Changed;
case LibFunc_pclose:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
return Changed;
Expand Down Expand Up @@ -733,16 +755,19 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_opendir:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setRetDoesNotAlias(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_tmpfile:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setRetDoesNotAlias(F);
return Changed;
case LibFunc_times:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
return Changed;
Expand All @@ -754,18 +779,22 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotAccessMemory(F);
return Changed;
case LibFunc_lstat:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setDoesNotCapture(F, 1);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_lchown:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setOnlyReadsMemory(F, 0);
return Changed;
case LibFunc_qsort:
// May throw; places call through function pointer.
// Cannot give undef pointer/size
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotCapture(F, 3);
return Changed;
case LibFunc_dunder_strdup:
Expand Down Expand Up @@ -799,6 +828,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
case LibFunc_stat64:
case LibFunc_lstat64:
case LibFunc_statvfs64:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setDoesNotCapture(F, 1);
Expand Down Expand Up @@ -828,6 +858,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
Changed |= setDoesNotCapture(F, 0);
return Changed;
case LibFunc_tmpfile64:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setRetDoesNotAlias(F);
return Changed;
Expand All @@ -847,6 +878,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
// Currently some platforms have the restrict keyword on the arguments to
// gettimeofday. To be conservative, do not add noalias to gettimeofday's
// arguments.
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotThrow(F);
Changed |= setDoesNotCapture(F, 0);
Changed |= setDoesNotCapture(F, 1);
Expand Down Expand Up @@ -874,6 +906,7 @@ bool llvm::inferLibFuncAttributes(Function &F, const TargetLibraryInfo &TLI) {
return Changed;
// int __nvvm_reflect(const char *)
case LibFunc_nvvm_reflect:
Changed |= setRetAndArgsNoUndef(F);
Changed |= setDoesNotAccessMemory(F);
Changed |= setDoesNotThrow(F);
return Changed;
Expand Down

0 comments on commit 36c8621

Please sign in to comment.