Re: [PATCH v2] rs6000: Fix some issues in rs6000_can_inline_p [PR102059]

["Kewen.Lin" <linkw@linux.ibm.com>]

[-- Attachment #1: Type: text/plain, Size: 7096 bytes --]

Hi Segher,

on 2021/12/6 下午9:06, Segher Boessenkool wrote:
> On Fri, Dec 03, 2021 at 11:46:53AM +0800, Kewen.Lin wrote:
>>>> This patch is to fix the inconsistent behaviors for non-LTO mode
>>>> and LTO mode.  As Martin pointed out, currently the function
>>>> rs6000_can_inline_p simply makes it inlinable if callee_tree is
>>>> NULL, but it's wrong, we should use the command line options
>>>> from target_option_default_node as default.
>>>
>>> This is not documented.
>>
>> Yeah, but according to the document for the target attribute [1],
>> "Multiple target back ends implement the target attribute to specify
>> that a function is to be compiled with different target options than
>> specified on the command line. The original target command-line options
>> are ignored. ", it seems to say the function without any target
>> attribute/pragma will be compiled with target options specified on the
>> command line.  I think it's a normal expectation for users.
> 
> The whole target_option_default_node is not documented, I meant.
> 

Ah, you meant that.  Yeah, it can be improved separately.

>> Excepting for the inconsistent behaviors between LTO and non-LTO,
>> it can also make the below case different.
>>
>> // Option: -O2 -mcpu=power8 -mhtm
>>
>> int foo(int *b) {
>>   *b += __builtin_ttest();
>>   return *b;
>> }
>>
>> __attribute__((target("no-htm"))) int bar(int *a) {
>>   *a = foo(a);
>>   return 0;
>> }
>>
>> Without this fix, bar inlines foo but get the error as below:
>>
>> In function ‘foo’,
>>     inlined from ‘bar’ at test.c:8:8:
>> test.c:3:9: error: ‘__builtin_ttest’ requires the ‘-mhtm’ option
>>     3 |   *b += __builtin_ttest();
>>       |         ^~~~~~~~~~~~~~~~~
>>
>> Since bar doesn't support foo's required HTM feature.
>>
>> With this fix, bar doesn't inline foo and the case gets compiled well.
> 
> And if you inline something no-htm into something that allows htm?  That
> should work fine, be allowed just fine.
> 

Thanks for helping to answer this, Peter!

>>>> It also replaces
>>>> rs6000_isa_flags with the one from target_option_default_node
>>>> when caller_tree is NULL as rs6000_isa_flags could probably
>>>> change since initialization.
>>>
>>> Is this enough then?  Are there no other places that use
>>> rs6000_isa_flags?  Is it correct for us to have that variable at all
>>> anymore?  Etc.
>>
>> Good question, I think the answer is yes.  I digged into it and found
>> the current target option save/restore scheme would keep rs6000_isa_flags
>> to be the same as the one saved in target_option_default_node for the context
>> of inlining.  So I put one assertion as below:
>>
>>     if (!caller_tree) {
>>       caller_tree = target_option_default_node;
>>       gcc_assert (rs6000_isa_flags
>>                   == TREE_TARGET_OPTION (caller_tree)->x_rs6000_isa_flags);
>>     }
>>
>> And kicked off regression testings on both BE and LE, the result showed
>> only one same failure, which seems to be a latent bug.  I've filed PR103515
>> for it.
> 
> Ah cool :-)  Please send a patch to add that asser then (well, once we
> can bootstrap with it ;-) )
> 

OK.

>> This bug also indicates it's better to use target_option_default_node
>> rather than rs6000_isa_flags when the caller_tree is NULL.  Since
>> the target_option_default_node is straightforward and doesn't rely
>> on the assumption that rs6000_isa_flags would be kept as the default
>> one correctly, it doesn't suffer from bugs like PR103515.
> 
> So we should not ever use rs6000_isa_flags anymore?
> 

If the question is for the scope in function rs6000_can_inline_p, yes.

Before this patch, the only use of rs6000_isa_flags is:

   /* If the caller has option attributes, then use them.
      Otherwise, use the command line options.  */
      if (caller_tree)
	caller_isa = TREE_TARGET_OPTION (caller_tree)->x_rs6000_isa_flags;
      else
	caller_isa = rs6000_isa_flags;

This patch changes this part to be like (logically):

      if (caller_tree)
	caller_isa = TREE_TARGET_OPTION (caller_tree)->x_rs6000_isa_flags;
      else
	caller_isa = TREE_TARGET_OPTION (target_option_default_node)->x_rs6000_isa_flags;

If the question is for the others out of function rs6000_can_inline_p, no.
The rs6000_isa_flags holds the flags for the current context of either top level
or some given function decl.  As function rs6000_set_current_function shows, we
already consider target_option_default_node for the case that there is NULL
DECL_FUNCTION_SPECIFIC_TARGET for one decl.

>>> The fusion ones are obvious.  The other two are not.  Please put those
>>> two more obviously separate (not somewhere in the sea of fusion
>>> options), and some comment wouldn't hurt either.  You can make it
>>> separate statements even, make it really stand out.
>>>
>>
>> Fixed by splitting it into: fusion_options_mask and optimization_options_mask.
>> I'm not happy for the later name, but poor to get a better in mind.  Do you
>> have any suggestions on the name and words?
> 
> You dont have to split it into variables, as you found out then you get
> the usual naming problem.  But you can just split it in the code:
> 
>   if (important_condition
>       || another_important_one
>       /* comment explaining things */
>       || bla1 || bla2 || bla3 || bla4 || bla5)
> 

Got it, thanks.  Removed those two variables and updated it to:

  /* Some features can be tolerated for always inlines.  */
  unsigned HOST_WIDE_INT always_inline_safe_mask
    /* Fusion option masks.  */
    = OPTION_MASK_P8_FUSION | OPTION_MASK_P10_FUSION
      | OPTION_MASK_P8_FUSION_SIGN | OPTION_MASK_P10_FUSION
      | OPTION_MASK_P10_FUSION_LD_CMPI | OPTION_MASK_P10_FUSION_2LOGICAL
      | OPTION_MASK_P10_FUSION_LOGADD | OPTION_MASK_P10_FUSION_ADDLOG
      | OPTION_MASK_P10_FUSION_2ADD
      /* Like fusion, some option masks which are just for optimization.  */
      | OPTION_MASK_SAVE_TOC_INDIRECT | OPTION_MASK_PCREL_OPT;

>>> Why are there OPTION_MASKs for separate P10 fusion types here, as well as
>>> MASK_P10_FUSION?
>>
>> Mike helped to explain the history, I've updated all of them using OPTION_MASK_
>> to avoid potential confusion.
> 
> That is one thing, sure, but why are both needed?  Both the "main" flag,
> and the "details" flags.

Because they are taken as independent bits in the below checking with bitwise
manipulation, like:

  (caller_isa & callee_isa) == callee_isa)

> 
> (The latter should soon go away btw).
> 
> 
> Segher
> 

The updated patch is attached, just changing always_inline_safe_mask
should be no any functional changes comparing to the previous version.

Does it look good to you?

BR,
Kewen
---
gcc/ChangeLog:

	PR ipa/102059
	* config/rs6000/rs6000.c (rs6000_can_inline_p): Adjust with
	target_option_default_node and consider always_inline_safe flags.

gcc/testsuite/ChangeLog:

	PR ipa/102059
	* gcc.target/powerpc/pr102059-1.c: New test.
	* gcc.target/powerpc/pr102059-2.c: New test.
	* gcc.target/powerpc/pr102059-3.c: New test.
	* gcc.target/powerpc/pr102059-4.c: New test.
	* gcc.target/powerpc/pr102059-5.c: New test.

-----

[-- Attachment #2: PR102059_v3.patch --]
[-- Type: text/plain, Size: 10829 bytes --]

---
 gcc/config/rs6000/rs6000.c                    | 91 ++++++++++++------
 gcc/testsuite/gcc.target/powerpc/pr102059-1.c | 24 +++++
 gcc/testsuite/gcc.target/powerpc/pr102059-2.c | 20 ++++
 gcc/testsuite/gcc.target/powerpc/pr102059-3.c | 95 +++++++++++++++++++
 gcc/testsuite/gcc.target/powerpc/pr102059-4.c | 22 +++++
 gcc/testsuite/gcc.target/powerpc/pr102059-5.c | 22 +++++
 6 files changed, 246 insertions(+), 28 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr102059-1.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr102059-2.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr102059-3.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr102059-4.c
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr102059-5.c

diff --git a/gcc/config/rs6000/rs6000.c b/gcc/config/rs6000/rs6000.c
index 289c1b3df24..856bd271a14 100644
--- a/gcc/config/rs6000/rs6000.c
+++ b/gcc/config/rs6000/rs6000.c
@@ -25539,45 +25539,80 @@ rs6000_generate_version_dispatcher_body (void *node_p)
 static bool
 rs6000_can_inline_p (tree caller, tree callee)
 {
-  bool ret = false;
   tree caller_tree = DECL_FUNCTION_SPECIFIC_TARGET (caller);
   tree callee_tree = DECL_FUNCTION_SPECIFIC_TARGET (callee);
 
-  /* If the callee has no option attributes, then it is ok to inline.  */
+  /* If the caller/callee has option attributes, then use them.
+     Otherwise, use the command line options.  */
   if (!callee_tree)
-    ret = true;
+    callee_tree = target_option_default_node;
+  if (!caller_tree)
+    caller_tree = target_option_default_node;
+
+  struct cl_target_option *caller_opts = TREE_TARGET_OPTION (caller_tree);
+  struct cl_target_option *callee_opts = TREE_TARGET_OPTION (callee_tree);
+  HOST_WIDE_INT caller_isa = caller_opts->x_rs6000_isa_flags;
+  HOST_WIDE_INT callee_isa = callee_opts->x_rs6000_isa_flags;
+
+  bool always_inline
+    = DECL_DISREGARD_INLINE_LIMITS (callee)
+      && lookup_attribute ("always_inline", DECL_ATTRIBUTES (callee));
+
+  /* Some features can be tolerated for always inlines.  */
+  unsigned HOST_WIDE_INT always_inline_safe_mask
+    /* Fusion option masks.  */
+    = OPTION_MASK_P8_FUSION | OPTION_MASK_P10_FUSION
+      | OPTION_MASK_P8_FUSION_SIGN | OPTION_MASK_P10_FUSION
+      | OPTION_MASK_P10_FUSION_LD_CMPI | OPTION_MASK_P10_FUSION_2LOGICAL
+      | OPTION_MASK_P10_FUSION_LOGADD | OPTION_MASK_P10_FUSION_ADDLOG
+      | OPTION_MASK_P10_FUSION_2ADD
+      /* Like fusion, some option masks which are just for optimization.  */
+      | OPTION_MASK_SAVE_TOC_INDIRECT | OPTION_MASK_PCREL_OPT;
+
+  /* To adjust callee is enough since we just check for subset.  */
+  if (always_inline)
+    callee_isa &= ~always_inline_safe_mask;
+
+  /* The callee's options must be a subset of the caller's options, i.e.
+     a vsx function may inline an altivec function, but a no-vsx function
+     must not inline a vsx function.  */
+  if ((caller_isa & callee_isa) != callee_isa)
+    {
+      if (TARGET_DEBUG_TARGET)
+	fprintf (stderr,
+		 "rs6000_can_inline_p:, caller %s, callee %s, cannot "
+		 "inline since callee's options set isn't a subset of "
+		 "caller's options set.\n",
+		 get_decl_name (caller), get_decl_name (callee));
+      return false;
+    }
 
-  else
+  /* For those options that the callee has explicitly enabled or disabled,
+     then we must enforce that the callee's and caller's options match
+     exactly; see PR70010.  */
+  HOST_WIDE_INT explicit_isa = callee_opts->x_rs6000_isa_flags_explicit;
+  if (always_inline)
+    explicit_isa &= ~always_inline_safe_mask;
+  if ((caller_isa & explicit_isa) != (callee_isa & explicit_isa))
     {
-      HOST_WIDE_INT caller_isa;
-      struct cl_target_option *callee_opts = TREE_TARGET_OPTION (callee_tree);
-      HOST_WIDE_INT callee_isa = callee_opts->x_rs6000_isa_flags;
-      HOST_WIDE_INT explicit_isa = callee_opts->x_rs6000_isa_flags_explicit;
-
-      /* If the caller has option attributes, then use them.
-	 Otherwise, use the command line options.  */
-      if (caller_tree)
-	caller_isa = TREE_TARGET_OPTION (caller_tree)->x_rs6000_isa_flags;
-      else
-	caller_isa = rs6000_isa_flags;
-
-      /* The callee's options must be a subset of the caller's options, i.e.
-	 a vsx function may inline an altivec function, but a no-vsx function
-	 must not inline a vsx function.  However, for those options that the
-	 callee has explicitly enabled or disabled, then we must enforce that
-	 the callee's and caller's options match exactly; see PR70010.  */
-      if (((caller_isa & callee_isa) == callee_isa)
-	  && (caller_isa & explicit_isa) == (callee_isa & explicit_isa))
-	ret = true;
+      if (TARGET_DEBUG_TARGET)
+	fprintf (stderr,
+		 "rs6000_can_inline_p:, caller %s, callee %s, cannot "
+		 "inline since callee's options set isn't a subset of "
+		 "caller's options set by considering callee's "
+		 "explicitly set options.\n",
+		 get_decl_name (caller), get_decl_name (callee));
+      return false;
     }
 
   if (TARGET_DEBUG_TARGET)
-    fprintf (stderr, "rs6000_can_inline_p:, caller %s, callee %s, %s inline\n",
-	     get_decl_name (caller), get_decl_name (callee),
-	     (ret ? "can" : "cannot"));
+    fprintf (stderr,
+	     "rs6000_can_inline_p:, caller %s, callee %s, can inline.\n",
+	     get_decl_name (caller), get_decl_name (callee));
 
-  return ret;
+  return true;
 }
+
 \f
 /* Allocate a stack temp and fixup the address so it meets the particular
    memory requirements (either offetable or REG+REG addressing).  */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr102059-1.c b/gcc/testsuite/gcc.target/powerpc/pr102059-1.c
new file mode 100644
index 00000000000..d2a002cf141
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr102059-1.c
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target powerpc_htm_ok } */
+/* { dg-options "-O2 -mdejagnu-cpu=power8" } */
+
+/* Verify it emits inlining error msg at non-LTO mode.  */
+
+#include <htmintrin.h>
+
+static inline int __attribute__ ((always_inline))
+foo (int *b) /* { dg-error "inlining failed in call to .* target specific option mismatch" } */
+{
+  int res = _HTM_STATE(__builtin_ttest());
+  *b += res;
+  return *b;
+}
+
+#pragma GCC target "cpu=power10"
+int
+bar (int *a)
+{
+  *a = foo (a); /* { dg-message "called from here" } */
+  return 0;
+}
+
diff --git a/gcc/testsuite/gcc.target/powerpc/pr102059-2.c b/gcc/testsuite/gcc.target/powerpc/pr102059-2.c
new file mode 100644
index 00000000000..1d5d6c38bf3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr102059-2.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mno-vsx" } */
+
+/* Verify it emits inlining error msg when the callee has explicit
+   disabling option from command line.  */
+
+vector int c, a, b;
+
+static inline void __attribute__ ((__always_inline__))
+foo () /* { dg-error "inlining failed in call to .* target specific option mismatch" } */
+{
+  c = a + b;
+}
+
+__attribute__ ((target ("vsx")))
+int main ()
+{
+  foo (); /* { dg-message "called from here" } */
+  c = a + b;
+}
diff --git a/gcc/testsuite/gcc.target/powerpc/pr102059-3.c b/gcc/testsuite/gcc.target/powerpc/pr102059-3.c
new file mode 100644
index 00000000000..9684cab986a
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr102059-3.c
@@ -0,0 +1,95 @@
+/* { dg-do compile } */
+/* -Wno-attributes suppresses always_inline warnings.  */
+/* { dg-options "-O2 -mdejagnu-cpu=power8 -Wno-attributes" } */
+
+/* Verify it doesn't emit inlining error msg since some mismatched
+   features are considered as safe for always_inline.  */
+
+/* 1. Callee enables Power8 fusion implicitly, while caller
+      with Power9 doesn't support power8 fusion at all.  */
+
+__attribute__ ((always_inline))
+int callee1 (int *b)
+{
+  *b += 1;
+  return *b;
+}
+
+#pragma GCC target "cpu=power9"
+int caller1 (int *a)
+{
+  *a = callee1 (a);
+  return 0;
+}
+
+/* 2. Caller enables indirect toc save feature while callee
+      disables it explicitly.  */
+
+#pragma GCC target "save-toc-indirect"
+__attribute__ ((always_inline))
+int callee2 (int *b)
+{
+  *b += 2;
+  return *b;
+}
+
+#pragma GCC target "no-save-toc-indirect"
+int caller2 (int *a)
+{
+  *a = callee2 (a);
+  return 0;
+}
+
+/* 3. Caller disables Power10 fusion explicitly, while callee
+      still supports it as Power10 turns it on by default.  */
+
+#pragma GCC target "cpu=power10"
+__attribute__ ((always_inline))
+int callee3 (int *b)
+{
+  *b += 3;
+  return *b;
+}
+
+#pragma GCC target "cpu=power10,no-power10-fusion"
+int caller3 (int *a)
+{
+  *a = callee3 (a);
+  return 0;
+}
+
+/* 4. Caller enables Power10 fusion implicitly, while callee
+      disables it explicitly.  */
+
+#pragma GCC target "no-power10-fusion"
+__attribute__ ((always_inline))
+int callee4 (int *b)
+{
+  *b += 4;
+  return *b;
+}
+
+#pragma GCC target "cpu=power10"
+int caller4 (int *a)
+{
+  *a = callee4 (a);
+  return 0;
+}
+
+/* 5. Caller disables pcrel-opt while callee enables it explicitly.  */
+
+#pragma GCC target "cpu=power10,no-pcrel-opt"
+__attribute__ ((always_inline))
+int callee5 (int *b)
+{
+  *b += 5;
+  return *b;
+}
+
+#pragma GCC target "cpu=power10,pcrel-opt"
+int caller5 (int *a)
+{
+  *a = callee5 (a);
+  return 0;
+}
+
diff --git a/gcc/testsuite/gcc.target/powerpc/pr102059-4.c b/gcc/testsuite/gcc.target/powerpc/pr102059-4.c
new file mode 100644
index 00000000000..0f27f2ce7d7
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr102059-4.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* -Wno-attributes suppresses always_inline warnings.  */
+/* { dg-options "-O2 -mdejagnu-cpu=power8 -mno-power8-fusion -Wno-attributes" } */
+
+/* Verify it doesn't emit inlining error msg since the flag power8
+   fusion is considered as safe for always_inline, it's still safe
+   even the flag is set explicitly.  */
+
+__attribute__ ((always_inline))
+int foo (int *b)
+{
+  *b += 10;
+  return *b;
+}
+
+#pragma GCC target "power8-fusion"
+int bar (int *a)
+{
+  *a = foo (a);
+  return 0;
+}
+
diff --git a/gcc/testsuite/gcc.target/powerpc/pr102059-5.c b/gcc/testsuite/gcc.target/powerpc/pr102059-5.c
new file mode 100644
index 00000000000..826ce88025f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr102059-5.c
@@ -0,0 +1,22 @@
+/* { dg-do compile } */
+/* { dg-require-effective-target powerpc_htm_ok } */
+/* { dg-options "-O2 -mdejagnu-cpu=power8 -mhtm" } */
+
+/* Verify the inlining won't perform when the callee requires
+   some target feature which isn't supported by caller, even
+   if the callee doesn't have any target attributes or pragmas.
+   If the inlining performs here, the compilation will fail.  */
+
+int
+foo (int *b)
+{
+  *b += __builtin_ttest ();
+  return *b;
+}
+
+__attribute__ ((target ("no-htm"))) int
+bar (int *a)
+{
+  *a = foo (a);
+  return 0;
+}
-- 
2.25.1