[gcc r13-4466] LRA: Check hard reg availability of pseudo and its subreg for pseudo reload

[Vladimir Makarov <vmakarov@gcc.gnu.org>]

https://gcc.gnu.org/g:70596a0fb2a2ec072e1e97e37616e05041dfa4e5

commit r13-4466-g70596a0fb2a2ec072e1e97e37616e05041dfa4e5
Author: Vladimir N. Makarov <vmakarov@redhat.com>
Date:   Fri Dec 2 08:18:04 2022 -0500

    LRA: Check hard reg availability of pseudo and its subreg for pseudo reload
    
    Do not reload subreg pseudo if there are hard regs for subreg mode
    but there are no hard regs for pseudo mode.
    
            PR target/106462
    
    gcc/ChangeLog:
    
            * lra-constraints.cc (curr_insn_transform): Check available hard
            regs for pseudo and its subreg to decide what to reload.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/mips/pr106462.c: New test.

Diff:
---
 gcc/lra-constraints.cc                   | 13 ++++++++++++-
 gcc/testsuite/gcc.target/mips/pr106462.c | 12 ++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index d92ab76908c..02b5ab4a316 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -4582,7 +4582,18 @@ curr_insn_transform (bool check_only_p)
 		      || (partial_subreg_p (mode, GET_MODE (reg))
 			  && known_le (GET_MODE_SIZE (GET_MODE (reg)),
 				       UNITS_PER_WORD)
-			  && WORD_REGISTER_OPERATIONS)))
+			  && WORD_REGISTER_OPERATIONS))
+		  /* Avoid the situation when there are no available hard regs
+		     for the pseudo mode but there are ones for the subreg
+		     mode: */
+		  && !(goal_alt[i] != NO_REGS
+		       && REGNO (reg) >= FIRST_PSEUDO_REGISTER
+		       && (prohibited_class_reg_set_mode_p
+			   (goal_alt[i], reg_class_contents[goal_alt[i]],
+			    GET_MODE (reg)))
+		       && !(prohibited_class_reg_set_mode_p
+			    (goal_alt[i], reg_class_contents[goal_alt[i]],
+			     mode))))
 		{
 		  /* An OP_INOUT is required when reloading a subreg of a
 		     mode wider than a word to ensure that data beyond the
diff --git a/gcc/testsuite/gcc.target/mips/pr106462.c b/gcc/testsuite/gcc.target/mips/pr106462.c
new file mode 100644
index 00000000000..c9105409524
--- /dev/null
+++ b/gcc/testsuite/gcc.target/mips/pr106462.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-mabi=64 -msingle-float" } */
+
+extern void bar (float x, short y);
+
+void foo (int argc)
+{
+    short c = argc * 2;
+    float a = (float)(short)c, b = 9.5;
+
+    bar (b/a, c);
+}