[gcc r10-9881] [PR98722] LRA: Check that target has no 3-op add insn to transform 2 plus expression.

[Przemyslaw Wirkus <wirkus@gcc.gnu.org>]

https://gcc.gnu.org/g:1791b11d9cae388ae18a768eeb96c998439c986a

commit r10-9881-g1791b11d9cae388ae18a768eeb96c998439c986a
Author: Vladimir N. Makarov <vmakarov@redhat.com>
Date:   Wed Jan 20 11:40:14 2021 -0500

    [PR98722] LRA: Check that target has no 3-op add insn to transform 2 plus expression.
    
    Patch cf2ac1c30af0fa783c8d72e527904dda5d8cc330 for solving PR97969 was
    assumed for targets with absent 3-op add insn.  But the original patch did
    not check this.  This patch adds the check.
    
    gcc/ChangeLog:
    
            PR rtl-optimization/98722
            * lra-eliminations.c (eliminate_regs_in_insn): Check that target
            has no 3-op add insn to transform insns containing two pluses.
    
    gcc/testsuite/ChangeLog:
    
            PR rtl-optimization/98722
            * g++.target/s390/pr98722.C: New.
    
    (cherry picked from commit 4334b524274203125193a08a8485250c41c2daa9)

Diff:
---
 gcc/lra-eliminations.c                  |  5 ++++-
 gcc/testsuite/g++.target/s390/pr98722.C | 12 ++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/gcc/lra-eliminations.c b/gcc/lra-eliminations.c
index e2d4b24db2a..d9e78d44312 100644
--- a/gcc/lra-eliminations.c
+++ b/gcc/lra-eliminations.c
@@ -1057,7 +1057,10 @@ eliminate_regs_in_insn (rtx_insn *insn, bool replace_p, bool first_p,
 	reg2 = SUBREG_REG (reg2);
       if (REG_P (reg1) && REG_P (reg2)
 	  && REGNO (reg1) < FIRST_PSEUDO_REGISTER
-	  && REGNO (reg2) >= FIRST_PSEUDO_REGISTER)
+	  && REGNO (reg2) >= FIRST_PSEUDO_REGISTER
+	  && GET_MODE (reg1) == Pmode
+	  && !have_addptr3_insn (gen_reg_rtx (Pmode), reg1,
+				 XEXP (XEXP (SET_SRC (set), 0), 1)))
 	{
 	  XEXP (XEXP (SET_SRC (set), 0), 0) = op2;
 	  XEXP (SET_SRC (set), 1) = op1;
diff --git a/gcc/testsuite/g++.target/s390/pr98722.C b/gcc/testsuite/g++.target/s390/pr98722.C
new file mode 100644
index 00000000000..64edaf3de21
--- /dev/null
+++ b/gcc/testsuite/g++.target/s390/pr98722.C
@@ -0,0 +1,12 @@
+// { dg-do compile }
+// { dg-options "-Og -fno-tree-fre -fno-split-wide-types" }
+struct B {
+  virtual void Method();
+};
+typedef void (B::*fn_type_a)();
+
+int main() {
+  fn_type_a f(&B::Method);
+  B b;
+  (b.*f)();
+}