[gcc r13-5761] RA: Implement reuse of equivalent memory for caller saves optimization (2nd version)

[gcc r13-5761] RA: Implement reuse of equivalent memory for caller saves optimization (2nd version)

[Vladimir Makarov]

https://gcc.gnu.org/g:10827a92f1a8c3207b327515f77845b34c1d9512

commit r13-5761-g10827a92f1a8c3207b327515f77845b34c1d9512
Author: Vladimir N. Makarov <vmakarov@redhat.com>
Date:   Thu Feb 9 15:18:48 2023 -0500

    RA: Implement reuse of equivalent memory for caller saves optimization (2nd version)
    
    The test pr103541.c shows opportunity to reuse memory with constant address for
    caller saves optimization for constant or pure function call.  The patch
    implements the memory reuse.
    
            PR rtl-optimization/103541
            PR rtl-optimization/108711
    
    gcc/ChangeLog:
    
            * ira.h (struct ira_reg_equiv_s): Add new field caller_save_p.
            * ira.cc (validate_equiv_mem): Check memref address variance.
            (no_equiv): Clear caller_save_p flag.
            (update_equiv_regs): Define caller save equivalence for
            valid_combine.
            (setup_reg_equiv): Clear defined_p flag for caller save equivalence.
            * lra-constraints.cc (lra_copy_reg_equiv): Add new arg
            call_save_p.  Use caller save equivalence depending on the arg.
            (split_reg): Adjust the call.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.target/i386/pr103541.c: New.
            * g++.target/i386/pr108711.C: New.

Diff:
---
 gcc/ira.cc                               | 21 ++++++++++++++++++---
 gcc/ira.h                                |  5 ++++-
 gcc/lra-constraints.cc                   | 15 +++++++++------
 gcc/testsuite/g++.target/i386/pr108711.C | 20 ++++++++++++++++++++
 gcc/testsuite/gcc.target/i386/pr103541.c | 14 ++++++++++++++
 5 files changed, 65 insertions(+), 10 deletions(-)

diff --git a/gcc/ira.cc b/gcc/ira.cc
index 66df03e8a59..6143db06c52 100644
--- a/gcc/ira.cc
+++ b/gcc/ira.cc
@@ -3070,6 +3070,8 @@ validate_equiv_mem_from_store (rtx dest, const_rtx set ATTRIBUTE_UNUSED,
     info->equiv_mem_modified = true;
 }
 
+static int equiv_init_varies_p (rtx x);
+
 enum valid_equiv { valid_none, valid_combine, valid_reload };
 
 /* Verify that no store between START and the death of REG invalidates
@@ -3113,7 +3115,8 @@ validate_equiv_mem (rtx_insn *start, rtx reg, rtx memref)
 	     been changed and all hell breaks loose.  */
 	  ret = valid_combine;
 	  if (!MEM_READONLY_P (memref)
-	      && !RTL_CONST_OR_PURE_CALL_P (insn))
+	      && (!RTL_CONST_OR_PURE_CALL_P (insn)
+		  || equiv_init_varies_p (XEXP (memref, 0))))
 	    return valid_none;
 	}
 
@@ -3414,6 +3417,7 @@ no_equiv (rtx reg, const_rtx store ATTRIBUTE_UNUSED,
   if (reg_equiv[regno].is_arg_equivalence)
     return;
   ira_reg_equiv[regno].defined_p = false;
+  ira_reg_equiv[regno].caller_save_p = false;
   ira_reg_equiv[regno].init_insns = NULL;
   for (; list; list = list->next ())
     {
@@ -3766,7 +3770,18 @@ update_equiv_regs (void)
 		{
 		  replacement = copy_rtx (SET_SRC (set));
 		  if (validity == valid_reload)
-		    note = set_unique_reg_note (insn, REG_EQUIV, replacement);
+		    {
+		      note = set_unique_reg_note (insn, REG_EQUIV, replacement);
+		    }
+		  else
+		    {
+		      /* We still can use this equivalence for caller save
+			 optimization in LRA.  Mark this.  */
+		      ira_reg_equiv[regno].caller_save_p = true;
+		      ira_reg_equiv[regno].init_insns
+			= gen_rtx_INSN_LIST (VOIDmode, insn,
+					     ira_reg_equiv[regno].init_insns);
+		    }
 		}
 	    }
 
@@ -4156,7 +4171,7 @@ setup_reg_equiv (void)
 		   legitimate, we ignore such REG_EQUIV notes.  */
 		if (memory_operand (x, VOIDmode))
 		  {
-		    ira_reg_equiv[i].defined_p = true;
+		    ira_reg_equiv[i].defined_p = !ira_reg_equiv[i].caller_save_p;
 		    ira_reg_equiv[i].memory = x;
 		    continue;
 		  }
diff --git a/gcc/ira.h b/gcc/ira.h
index 58b50dbe8a2..3d35025a46e 100644
--- a/gcc/ira.h
+++ b/gcc/ira.h
@@ -175,8 +175,11 @@ extern struct target_ira *this_target_ira;
 /* Major structure describing equivalence info for a pseudo.  */
 struct ira_reg_equiv_s
 {
-  /* True if we can use this equivalence.  */
+  /* True if we can use this as a general equivalence.  */
   bool defined_p;
+  /* True if we can use this equivalence only for caller save/restore
+     location.  */
+  bool caller_save_p;
   /* True if the usage of the equivalence is profitable.  */
   bool profitable_p;
   /* Equiv. memory, constant, invariant, and initializing insns of
diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 7bffbc07ee2..dd4f68bbfc0 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -5771,14 +5771,17 @@ choose_split_class (enum reg_class allocno_class,
   return best_cl;
 }
 
-/* Copy any equivalence information from ORIGINAL_REGNO to NEW_REGNO.
-   It only makes sense to call this function if NEW_REGNO is always
-   equal to ORIGINAL_REGNO.  */
+/* Copy any equivalence information from ORIGINAL_REGNO to NEW_REGNO.  It only
+   makes sense to call this function if NEW_REGNO is always equal to
+   ORIGINAL_REGNO.  Set up defined_p flag when caller_save_p flag is set up and
+   CALL_SAVE_P is true.  */
 
 static void
-lra_copy_reg_equiv (unsigned int new_regno, unsigned int original_regno)
+lra_copy_reg_equiv (unsigned int new_regno, unsigned int original_regno,
+		    bool call_save_p)
 {
-  if (!ira_reg_equiv[original_regno].defined_p)
+  if (!ira_reg_equiv[original_regno].defined_p
+      && !(call_save_p && ira_reg_equiv[original_regno].caller_save_p))
     return;
 
   ira_expand_reg_equiv ();
@@ -5958,7 +5961,7 @@ split_reg (bool before_p, int original_regno, rtx_insn *insn,
      rematerializing the original value instead of spilling to the stack.  */
   if (!HARD_REGISTER_NUM_P (original_regno)
       && mode == PSEUDO_REGNO_MODE (original_regno))
-    lra_copy_reg_equiv (new_regno, original_regno);
+    lra_copy_reg_equiv (new_regno, original_regno, call_save_p);
   lra_reg_info[new_regno].restore_rtx = regno_reg_rtx[original_regno];
   bitmap_set_bit (&lra_split_regs, new_regno);
   if (to != NULL)
diff --git a/gcc/testsuite/g++.target/i386/pr108711.C b/gcc/testsuite/g++.target/i386/pr108711.C
new file mode 100644
index 00000000000..0a223e005e5
--- /dev/null
+++ b/gcc/testsuite/g++.target/i386/pr108711.C
@@ -0,0 +1,20 @@
+/* PR target/108711.C */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-exceptions" } */
+struct Expression_list {
+  Expression_list *copy();
+} vals_;
+struct Parser_expression {
+  Parser_expression();
+};
+struct Composite_literal_expression : Parser_expression {
+  Composite_literal_expression(bool has_keys, Expression_list *,
+                               bool all_are_names)
+      : has_keys_(has_keys), all_are_names_(all_are_names) {}
+  void do_copy();
+  bool has_keys_;
+  bool all_are_names_;
+};
+void Composite_literal_expression::do_copy() {
+  new Composite_literal_expression(has_keys_, vals_.copy(), all_are_names_);
+}
diff --git a/gcc/testsuite/gcc.target/i386/pr103541.c b/gcc/testsuite/gcc.target/i386/pr103541.c
new file mode 100644
index 00000000000..72b257d42ee
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr103541.c
@@ -0,0 +1,14 @@
+/* PR rtl-optimization/103541 */
+/* { dg-do compile  { target x86_64-*-* } } */
+/* { dg-options "-O2" } */
+
+float a;
+__attribute__((const)) float foo (float);
+
+float
+test()
+{
+        return a + foo(a) + a;
+}
+
+/* { dg-final { scan-assembler-not "\\\(%rsp\\\)" } } */