gcc/0226-Backport-SME-riscv-Add-support-for-strlen-inline-exp.patch

From 637e6469f2225b6f6f6b0c84b4e7abcd8dfd7ca4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Christoph=20M=C3=BCllner?= <christoph.muellner@vrull.eu>
Date: Wed, 28 Sep 2022 11:19:06 +0200
Subject: [PATCH 127/157] [Backport][SME] riscv: Add support for strlen inline
 expansion
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Reference: https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=df48285b2484eb4f8e0570c566677114eb0e553a

Note: Only introduce the definitions of function
emit_likely_jump_insn and emit_unlikely_jump_insn,
and drop others.

This patch implements the expansion of the strlen builtin for RV32/RV64
for xlen-aligned aligned strings if Zbb or XTheadBb instructions are available.
The inserted sequences are:

rv32gc_zbb (RV64 is similar):
      add     a3,a0,4
      li      a4,-1
.L1:  lw      a5,0(a0)
      add     a0,a0,4
      orc.b   a5,a5
      beq     a5,a4,.L1
      not     a5,a5
      ctz     a5,a5
      srl     a5,a5,0x3
      add     a0,a0,a5
      sub     a0,a0,a3

rv64gc_xtheadbb (RV32 is similar):
      add       a4,a0,8
.L2:  ld        a5,0(a0)
      add       a0,a0,8
      th.tstnbz a5,a5
      beqz      a5,.L2
      th.rev    a5,a5
      th.ff1    a5,a5
      srl       a5,a5,0x3
      add       a0,a0,a5
      sub       a0,a0,a4

This allows to inline calls to strlen(), with optimized code for
xlen-aligned strings, resulting in the following benefits over
a call to libc:
* no call/ret instructions
* no stack frame allocation
* no register saving/restoring
* no alignment test

The inlining mechanism is gated by a new switch ('-minline-strlen')
and by the variable 'optimize_size'.

Tested using the glibc string tests.

Signed-off-by: Christoph Müllner <christoph.muellner@vrull.eu>

gcc/ChangeLog:

	* config.gcc: Add new object riscv-string.o.
	riscv-string.cc.
	* config/riscv/riscv-protos.h (riscv_expand_strlen):
	New function.
	* config/riscv/riscv.md (strlen<mode>): New expand INSN.
	* config/riscv/riscv.opt: New flag 'minline-strlen'.
	* config/riscv/t-riscv: Add new object riscv-string.o.
	* config/riscv/thead.md (th_rev<mode>2): Export INSN name.
	(th_rev<mode>2): Likewise.
	(th_tstnbz<mode>2): New INSN.
	* doc/invoke.texi: Document '-minline-strlen'.
	* emit-rtl.cc (emit_likely_jump_insn): New helper function.
	(emit_unlikely_jump_insn): Likewise.
	* rtl.h (emit_likely_jump_insn): New prototype.
	(emit_unlikely_jump_insn): Likewise.
	* config/riscv/riscv-string.cc: New file.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/xtheadbb-strlen-unaligned.c: New test.
	* gcc.target/riscv/xtheadbb-strlen.c: New test.
	* gcc.target/riscv/zbb-strlen-disabled-2.c: New test.
	* gcc.target/riscv/zbb-strlen-disabled.c: New test.
	* gcc.target/riscv/zbb-strlen-unaligned.c: New test.
	* gcc.target/riscv/zbb-strlen.c: New test.
---
 gcc/emit-rtl.cc | 24 ++++++++++++++++++++++++
 gcc/rtl.h       |  2 ++
 2 files changed, 26 insertions(+)

diff --git a/gcc/emit-rtl.cc b/gcc/emit-rtl.cc
index 1e02ae254..2df5ff414 100644
--- a/gcc/emit-rtl.cc
+++ b/gcc/emit-rtl.cc
@@ -5163,6 +5163,30 @@ emit_jump_insn (rtx x)
   return last;
 }
 
+/* Make an insn of code JUMP_INSN with pattern X,
+   add a REG_BR_PROB note that indicates very likely probability,
+   and add it to the end of the doubly-linked list.  */
+
+rtx_insn *
+emit_likely_jump_insn (rtx x)
+{
+  rtx_insn *jump = emit_jump_insn (x);
+  add_reg_br_prob_note (jump, profile_probability::very_likely ());
+  return jump;
+}
+
+/* Make an insn of code JUMP_INSN with pattern X,
+   add a REG_BR_PROB note that indicates very unlikely probability,
+   and add it to the end of the doubly-linked list.  */
+
+rtx_insn *
+emit_unlikely_jump_insn (rtx x)
+{
+  rtx_insn *jump = emit_jump_insn (x);
+  add_reg_br_prob_note (jump, profile_probability::very_unlikely ());
+  return jump;
+}
+
 /* Make an insn of code CALL_INSN with pattern X
    and add it to the end of the doubly-linked list.  */
 
diff --git a/gcc/rtl.h b/gcc/rtl.h
index 488016bb4..a0db225cb 100644
--- a/gcc/rtl.h
+++ b/gcc/rtl.h
@@ -3333,6 +3333,8 @@ extern rtx_note *emit_note_after (enum insn_note, rtx_insn *);
 extern rtx_insn *emit_insn (rtx);
 extern rtx_insn *emit_debug_insn (rtx);
 extern rtx_insn *emit_jump_insn (rtx);
+extern rtx_insn *emit_likely_jump_insn (rtx);
+extern rtx_insn *emit_unlikely_jump_insn (rtx);
 extern rtx_insn *emit_call_insn (rtx);
 extern rtx_code_label *emit_label (rtx);
 extern rtx_jump_table_data *emit_jump_table_data (rtx);
-- 
2.33.0