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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
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
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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
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