[PATCH V3] rs6000: cannot_force_const_mem for HIGH code rtx[PR106460]

[Jiufu Guo <guojiufu@linux.ibm.com>]

Hi,

As the issue in PR106460, a rtx 'high:DI (symbol_ref:DI ("var_48")' is tried
to store into constant pool and ICE occur.  But actually, this rtx represents
partial address and can not be put into a .rodata section.

This patch updates rs6000_cannot_force_const_mem to return true for rtx(s) with
HIGH code, because these rtx(s) indicate part of address and are not ok for
constant pool.

Below are some examples:
(high:DI (const:DI (plus:DI (symbol_ref:DI ("xx") (const_int 12 [0xc])))))
(high:DI (symbol_ref:DI ("var_1")..)))

This patch updated the previous patch, and drafted an test case which ICE
without the patch, and assoicated with one PR.
https://gcc.gnu.org/pipermail/gcc-patches/2022-July/597712.html
This patch also updated the message for previous patch V2.

I would ask help to review this patch one more time.

Bootstrap and regtest pass on ppc64 and ppc64le.
Is this ok for trunk.

BR,
Jeff(Jiufu)

	PR target/106460

gcc/ChangeLog:

	* config/rs6000/rs6000.cc (rs6000_cannot_force_const_mem): Return true
	for HIGH code rtx.

gcc/testsuite/ChangeLog:

	* gcc.target/powerpc/pr106460.c: New test.
---
 gcc/config/rs6000/rs6000.cc                 |  7 +++++--
 gcc/testsuite/gcc.target/powerpc/pr106460.c | 11 +++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/powerpc/pr106460.c

diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
index 2f3146e56f8..04e3a393147 100644
--- a/gcc/config/rs6000/rs6000.cc
+++ b/gcc/config/rs6000/rs6000.cc
@@ -9643,8 +9643,11 @@ rs6000_init_stack_protect_guard (void)
 static bool
 rs6000_cannot_force_const_mem (machine_mode mode ATTRIBUTE_UNUSED, rtx x)
 {
-  if (GET_CODE (x) == HIGH
-      && GET_CODE (XEXP (x, 0)) == UNSPEC)
+  /* If GET_CODE (x) is HIGH, the 'X' represets the high part of a symbol_ref.
+     It indicates partial address,  which can not be put into a constant pool.
+     e.g.  (high:DI (unspec:DI [(symbol_ref/u:DI ("*.LC0")..)
+     (high:DI (symbol_ref:DI ("var")..)).  */
+  if (GET_CODE (x) == HIGH)
     return true;
 
   /* A TLS symbol in the TOC cannot contain a sum.  */
diff --git a/gcc/testsuite/gcc.target/powerpc/pr106460.c b/gcc/testsuite/gcc.target/powerpc/pr106460.c
new file mode 100644
index 00000000000..dfaffcb6e28
--- /dev/null
+++ b/gcc/testsuite/gcc.target/powerpc/pr106460.c
@@ -0,0 +1,11 @@
+/* { dg-options "-O1 -mdejagnu-cpu=power10" } */
+
+/* (high:DI (symbol_ref:DI ("var_48")..))) should not cause ICE. */
+extern short var_48;
+void
+foo (double *r)
+{
+  if (var_48)
+    *r = 1234.5678;
+}
+
-- 
2.17.1