[PATCH v10 4/4] ree: Improve ree pass for rs6000 target using defined ABI interfaces

[PATCH v10 4/4] ree: Improve ree pass for rs6000 target using defined ABI interfaces

[Ajit Agarwal]

Hello Vineet and Jeff:

This version 10 of the patch uses abi interfaces to remove zero and sign extension elimination.
Bootstrapped and regtested on powerpc-linux-gnu.

In this version (version 9) of the patch following review comments are incorporated.

a) Removal of hard code zero_extend and sign_extend  in abi interfaces.
b) Source and destination with different registers are considered.
c) Further enhancements.
d) Added sign extension elimination using abi interfaces.
d) Addressed remaining review comments.

Please check if its addressed bootstrapped failure with RISC-V.
Also please let me know if there is anything missing in this patch.

Ok for trunk?

Thanks & Regards
Ajit


ree: Improve ree pass for rs6000 target using defined abi interfaces

For rs6000 target we see redundant zero and sign extension and done
to improve ree pass to eliminate such redundant zero and sign extension
using defined ABI interfaces.

2023-10-21  Ajit Kumar Agarwal  <aagarwa1@linux.ibm.com>

gcc/ChangeLog:

        * ree.cc (combine_reaching_defs): Use of zero_extend and sign_extend
        defined abi interfaces.
        (add_removable_extension): Use of defined abi interfaces for no
        reaching defs.
        (abi_extension_candidate_return_reg_p): New function.
        (abi_extension_candidate_p): New function.
        (abi_extension_candidate_argno_p): New function.
        (abi_handle_regs): New function.
        (abi_target_promote_function_mode): New function.

gcc/testsuite/ChangeLog:

        * g++.target/powerpc/zext-elim-3.C
---
 gcc/ree.cc                                    | 145 +++++++++++++++++-
 .../g++.target/powerpc/zext-elim-3.C          |  13 ++
 2 files changed, 154 insertions(+), 4 deletions(-)
 create mode 100644 gcc/testsuite/g++.target/powerpc/zext-elim-3.C

diff --git a/gcc/ree.cc b/gcc/ree.cc
index fc04249fa84..51b1aab165e 100644
--- a/gcc/ree.cc
+++ b/gcc/ree.cc
@@ -514,7 +514,8 @@ get_uses (rtx_insn *insn, rtx reg)
     if (REGNO (DF_REF_REG (def)) == REGNO (reg))
       break;
 
-  gcc_assert (def != NULL);
+  if (def == NULL)
+    return NULL;
 
   ref_chain = DF_REF_CHAIN (def);
 
@@ -750,6 +751,124 @@ get_extended_src_reg (rtx src)
   return src;
 }
 
+/* Return TRUE if target mode is equal to source mode of zero_extend
+   or sign_extend otherwise false.  */
+
+static bool
+abi_target_promote_function_mode (machine_mode mode)
+{
+  int unsignedp;
+  machine_mode tgt_mode
+    = targetm.calls.promote_function_mode (NULL_TREE, mode, &unsignedp,
+					   NULL_TREE, 1);
+
+  if (tgt_mode == mode)
+    return true;
+  else
+    return false;
+}
+
+/* Return TRUE if the candidate insn is zero extend and regno is
+   a return registers.  */
+
+static bool
+abi_extension_candidate_return_reg_p (/*rtx_insn *insn, */int regno)
+{
+  if (targetm.calls.function_value_regno_p (regno))
+    return true;
+
+  return false;
+}
+
+/* Return TRUE if reg source operand of zero_extend is argument registers
+   and not return registers and source and destination operand are same
+   and mode of source and destination operand are not same.  */
+
+static bool
+abi_extension_candidate_p (rtx_insn *insn)
+{
+  rtx set = single_set (insn);
+  machine_mode dst_mode = GET_MODE (SET_DEST (set));
+  rtx orig_src = XEXP (SET_SRC (set), 0);
+
+  if (!FUNCTION_ARG_REGNO_P (REGNO (orig_src))
+      || abi_extension_candidate_return_reg_p (/*insn,*/ REGNO (orig_src)))
+    return false;
+
+  /* Mode of destination and source should be different.  */
+  if (dst_mode == GET_MODE (orig_src))
+    return false;
+
+  machine_mode mode = GET_MODE (XEXP (SET_SRC (set), 0));
+  bool promote_p = abi_target_promote_function_mode (mode);
+
+  /* REGNO of source and destination should be same if not
+      promoted.  */
+  if (!promote_p && REGNO (SET_DEST (set)) != REGNO (orig_src))
+    return false;
+
+  return true;
+}
+
+/* Return TRUE if the candidate insn is zero extend and regno is
+   an argument registers.  */
+
+static bool
+abi_extension_candidate_argno_p (/*rtx_code code, */int regno)
+{
+  if (FUNCTION_ARG_REGNO_P (regno))
+    return true;
+
+  return false;
+}
+
+/* Return TRUE if the candidate insn doesn't have defs and have
+ * uses without RTX_BIN_ARITH/RTX_COMM_ARITH/RTX_UNARY rtx class.  */
+
+static bool
+abi_handle_regs (rtx_insn *insn)
+{
+  if (side_effects_p (PATTERN (insn)))
+    return false;
+
+  struct df_link *uses = get_uses (insn, SET_DEST (PATTERN (insn)));
+
+  if (!uses)
+    return false;
+
+  for (df_link *use = uses; use; use = use->next)
+    {
+      if (!use->ref)
+	return false;
+
+      if (BLOCK_FOR_INSN (insn) != BLOCK_FOR_INSN (DF_REF_INSN (use->ref)))
+	return false;
+
+      rtx_insn *use_insn = DF_REF_INSN (use->ref);
+
+      if (GET_CODE (PATTERN (use_insn)) == SET)
+	{
+	  rtx_code code = GET_CODE (SET_SRC (PATTERN (use_insn)));
+
+	  if (GET_RTX_CLASS (code) == RTX_BIN_ARITH
+	      || GET_RTX_CLASS (code) == RTX_COMM_ARITH
+	      || GET_RTX_CLASS (code) == RTX_UNARY)
+	    return false;
+	}
+     }
+
+  rtx set = single_set (insn);
+
+  if (GET_CODE (SET_SRC (set)) == SIGN_EXTEND)
+    {
+      machine_mode mode = GET_MODE (XEXP (SET_SRC (set), 0));
+      bool promote_p = abi_target_promote_function_mode (mode);
+
+      return promote_p;
+    }
+  return true;
+}
+
 /* This function goes through all reaching defs of the source
    of the candidate for elimination (CAND) and tries to combine
    the extension with the definition instruction.  The changes
@@ -770,6 +889,11 @@ combine_reaching_defs (ext_cand *cand, const_rtx set_pat, ext_state *state)
 
   state->defs_list.truncate (0);
   state->copies_list.truncate (0);
+  rtx orig_src = XEXP (SET_SRC (cand->expr),0);
+
+  if (abi_extension_candidate_p (cand->insn)
+      && (!get_defs (cand->insn, orig_src, NULL)))
+    return abi_handle_regs (cand->insn);
 
   outcome = make_defs_and_copies_lists (cand->insn, set_pat, state);
 
@@ -1112,13 +1236,16 @@ add_removable_extension (const_rtx expr, rtx_insn *insn,
       rtx reg = XEXP (src, 0);
       struct df_link *defs, *def;
       ext_cand *cand;
+      defs = get_defs (insn, reg, NULL);
 
       /* Zero-extension of an undefined value is partly defined (it's
 	 completely undefined for sign-extension, though).  So if there exists
 	 a path from the entry to this zero-extension that leaves this register
 	 uninitialized, removing the extension could change the behavior of
 	 correct programs.  So first, check it is not the case.  */
-      if (code == ZERO_EXTEND && !bitmap_bit_p (init_regs, REGNO (reg)))
+      if (code == ZERO_EXTEND
+	  && !bitmap_bit_p (init_regs, REGNO (reg))
+	  && !abi_extension_candidate_argno_p (REGNO (reg)))
 	{
 	  if (dump_file)
 	    {
@@ -1131,9 +1258,14 @@ add_removable_extension (const_rtx expr, rtx_insn *insn,
 	}
 
       /* Second, make sure we can get all the reaching definitions.  */
-      defs = get_defs (insn, reg, NULL);
       if (!defs)
 	{
+	  if (abi_extension_candidate_argno_p (REGNO (reg)))
+	    {
+	      ext_cand e = {expr, code, mode, insn};
+	      insn_list->safe_push (e);
+	      return;
+	    }
 	  if (dump_file)
 	    {
 	      fprintf (dump_file, "Cannot eliminate extension:\n");
@@ -1321,7 +1453,8 @@ find_and_remove_re (void)
 	      && (REGNO (SET_DEST (set)) != REGNO (XEXP (SET_SRC (set), 0))))
 	    {
               reinsn_copy_list.safe_push (curr_cand->insn);
-              reinsn_copy_list.safe_push (state.defs_list[0]);
+	      if (state.defs_list.length () != 0)
+		reinsn_copy_list.safe_push (state.defs_list[0]);
 	    }
 	  reinsn_del_list.safe_push (curr_cand->insn);
 	  state.modified[INSN_UID (curr_cand->insn)].deleted = 1;
@@ -1345,6 +1478,10 @@ find_and_remove_re (void)
   for (unsigned int i = 0; i < reinsn_copy_list.length (); i += 2)
     {
       rtx_insn *curr_insn = reinsn_copy_list[i];
+
+      if ((i+1) >= reinsn_copy_list.length ())
+	continue;
+
       rtx_insn *def_insn = reinsn_copy_list[i + 1];
 
       /* Use the mode of the destination of the defining insn
diff --git a/gcc/testsuite/g++.target/powerpc/zext-elim-3.C b/gcc/testsuite/g++.target/powerpc/zext-elim-3.C
new file mode 100644
index 00000000000..5a050df06ff
--- /dev/null
+++ b/gcc/testsuite/g++.target/powerpc/zext-elim-3.C
@@ -0,0 +1,13 @@
+/* { dg-options "-mcpu=power9 -O2" } */
+
+void *memset(void *b, int c, unsigned long len)
+{
+  unsigned long i;
+
+  for (i = 0; i < len; i++)
+    ((unsigned char *)b)[i] = c;
+
+   return b;
+}
+
+/* { dg-final { scan-assembler-not "\mrlwinm\M" } } */
-- 
2.39.3