rs6000: Skip empty inline asm in rs6000_update_ipa_fn_target_info [PR111366]

PR111366 exposes one thing that can be improved in function
rs6000_update_ipa_fn_target_info is to skip the given empty
inline asm string, since it's impossible to adopt any
hardware features (so far HTM).

Since this rs6000_update_ipa_fn_target_info related approach
exists in GCC12 and later, the affected project highway has
updated its target pragma with ",htm", see the link:
https://github.com/google/highway/commit/15e63d61eb535f478bc
I'd not bother to consider an inline asm parser for now but
will file a separated PR for further enhancement.

	PR target/111366

gcc/ChangeLog:

	* config/rs6000/rs6000.cc (rs6000_update_ipa_fn_target_info): Skip
	empty inline asm.

gcc/testsuite/ChangeLog:

	* g++.target/powerpc/pr111366.C: New test.

2 files changed, 54 insertions, 3 deletions

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index e6c0486..cc9253b 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -25477,9 +25477,12 @@ rs6000_update_ipa_fn_target_info (unsigned int &info, const gimple *stmt)
   /* Assume inline asm can use any instruction features.  */
   if (gimple_code (stmt) == GIMPLE_ASM)
     {
-      /* Should set any bits we concerned, for now OPTION_MASK_HTM is
-	 the only bit we care about.  */
-      info |= RS6000_FN_TARGET_INFO_HTM;
+      const char *asm_str = gimple_asm_string (as_a<const gasm *> (stmt));
+      /* Ignore empty inline asm string.  */
+      if (strlen (asm_str) > 0)
+	/* Should set any bits we concerned, for now OPTION_MASK_HTM is
+	   the only bit we care about.  */
+	info |= RS6000_FN_TARGET_INFO_HTM;
       return false;
     }
   else if (gimple_code (stmt) == GIMPLE_CALL)
diff --git a/gcc/testsuite/g++.target/powerpc/pr111366.C b/gcc/testsuite/g++.target/powerpc/pr111366.C
new file mode 100644
index 0000000..6d3d8eb
--- /dev/null
+++ b/gcc/testsuite/g++.target/powerpc/pr111366.C
@@ -0,0 +1,48 @@
+/* { dg-do compile } */
+/* Use -Wno-attributes to suppress the possible warning on always_inline.  */
+/* { dg-options "-O2 -mdejagnu-cpu=power9 -Wno-attributes" } */
+
+/* Verify it doesn't emit any error messages.  */
+
+#include <stddef.h>
+#define HWY_PRAGMA(tokens) _Pragma (#tokens)
+#define HWY_PUSH_ATTRIBUTES(targets_str) HWY_PRAGMA (GCC target targets_str)
+__attribute__ ((always_inline)) void
+PreventElision ()
+{
+  asm("");
+}
+#define HWY_BEFORE_NAMESPACE() HWY_PUSH_ATTRIBUTES (",cpu=power10")
+HWY_BEFORE_NAMESPACE () namespace detail
+{
+  template <typename, size_t, int> struct CappedTagChecker
+  {
+  };
+}
+template <typename T, size_t kLimit, int kPow2 = 0>
+using CappedTag = detail::CappedTagChecker<T, kLimit, kPow2>;
+template <typename, size_t, size_t kMinArg, class Test> struct ForeachCappedR
+{
+  static void Do (size_t, size_t)
+  {
+    CappedTag<int, kMinArg> d;
+    Test () (int(), d);
+  }
+};
+template <class Test> struct ForPartialVectors
+{
+  template <typename T> void operator() (T)
+  {
+    ForeachCappedR<T, 1, 1, Test>::Do (1, 1);
+  }
+};
+struct TestFloorLog2
+{
+  template <class T, class DF> void operator() (T, DF) { PreventElision (); }
+};
+void
+TestAllFloorLog2 ()
+{
+  ForPartialVectors<TestFloorLog2> () (float());
+}
+