Re: Add -fipa-strict-aliasing

[Jan Hubicka via Gcc-patches]

Hi,
this is a variant I comitted (with updated documentation as Richard
requested).
Honza

gcc/ChangeLog:

2021-12-13  Jan Hubicka  <hubi...@ucw.cz>

        * common.opt: Add -fipa-strict-aliasing.
        * doc/invoke.texi: Document -fipa-strict-aliasing.
        * ipa-modref.c (modref_access_analysis::record_access): Honor
        -fipa-strict-aliasing.
        (modref_access_analysis::record_access_lto): Likewise.

diff --git a/gcc/common.opt b/gcc/common.opt
index 445a53a265c..8f8fc2f9ee7 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1945,6 +1945,10 @@ fira-algorithm=
 Common Joined RejectNegative Enum(ira_algorithm) Var(flag_ira_algorithm) 
Init(IRA_ALGORITHM_CB) Optimization
 -fira-algorithm=[CB|priority]  Set the used IRA algorithm.
 
+fipa-strict-aliasing
+Common Var(flag_ipa_strict_aliasing) Init(1) Optimization
+Assume strict aliasing rules apply across (uninlined) function boundaries.
+
 Enum
 Name(ira_algorithm) Type(enum ira_algorithm) UnknownError(unknown IRA 
algorithm %qs)
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 9b4371b9213..e9f66287098 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -570,7 +570,7 @@ Objective-C and Objective-C++ Dialects}.
 -fsingle-precision-constant  -fsplit-ivs-in-unroller  -fsplit-loops@gol
 -fsplit-paths @gol
 -fsplit-wide-types  -fsplit-wide-types-early  -fssa-backprop  -fssa-phiopt @gol
--fstdarg-opt  -fstore-merging  -fstrict-aliasing @gol
+-fstdarg-opt  -fstore-merging  -fstrict-aliasing -fipa-strict-aliasing @gol
 -fthread-jumps  -ftracer  -ftree-bit-ccp @gol
 -ftree-builtin-call-dce  -ftree-ccp  -ftree-ch @gol
 -ftree-coalesce-vars  -ftree-copy-prop  -ftree-dce  -ftree-dominator-opts @gol
@@ -12423,6 +12423,16 @@ int f() @{
 The @option{-fstrict-aliasing} option is enabled at levels
 @option{-O2}, @option{-O3}, @option{-Os}.
 
+@item -fipa-strict-aliasing
+@opindex fipa-strict-aliasing
+Constrols whether rules of @option{-fstrict-aliasing} are applied across
+function boundaries.  Note that if multiple functions gets inlined into a
+signle function the memory accesses are no longer considred to be crossing a
+function bounday.
+
+The @option{-fipa-strict-aliasing} option is enabled by default and is
+effective only in combination with @option{-fstrict-aliasing}.
+
 @item -falign-functions
 @itemx -falign-functions=@var{n}
 @itemx -falign-functions=@var{n}:@var{m}
diff --git a/gcc/ipa-modref.c b/gcc/ipa-modref.c
index 2c89c63baf6..d6bd9d33278 100644
--- a/gcc/ipa-modref.c
+++ b/gcc/ipa-modref.c
@@ -999,9 +999,11 @@ modref_access_analysis::record_access (modref_records *tt,
                                       ao_ref *ref,
                                       modref_access_node &a)
 {
-  alias_set_type base_set = !flag_strict_aliasing ? 0
+  alias_set_type base_set = !flag_strict_aliasing
+                           || !flag_ipa_strict_aliasing ? 0
                            : ao_ref_base_alias_set (ref);
-  alias_set_type ref_set = !flag_strict_aliasing ? 0
+  alias_set_type ref_set = !flag_strict_aliasing
+                          || !flag_ipa_strict_aliasing ? 0
                            : (ao_ref_alias_set (ref));
   if (dump_file)
     {
@@ -1021,7 +1023,7 @@ modref_access_analysis::record_access_lto 
(modref_records_lto *tt, ao_ref *ref,
   /* get_alias_set sometimes use different type to compute the alias set
      than TREE_TYPE (base).  Do same adjustments.  */
   tree base_type = NULL_TREE, ref_type = NULL_TREE;
-  if (flag_strict_aliasing)
+  if (flag_strict_aliasing && flag_ipa_strict_aliasing)
     {
       tree base;