From 7c8ba5da80d5d95a8521010d6731d0d83036145d Mon Sep 17 00:00:00 2001
From: David Faust <david.faust@oracle.com>
Date: Tue, 22 Sep 2020 20:31:35 +0200
Subject: [PATCH] bpf: use xBPF signed div, mod insns when available

The 'mod' and 'div' operators in eBPF are unsigned, with no signed
counterpart. xBPF adds two new ALU operations, sdiv and smod, for
signed division and modulus, respectively. Update bpf.md with
'define_insn' blocks for signed div and mod to use them when targetting
xBPF, and add new tests to ensure they are used appropriately.

2020-09-17  David Faust  <david.faust@oracle.com>

gcc/
	* config/bpf/bpf.md: Add defines for signed div and mod operators.

gcc/testsuite/
	* gcc.target/bpf/diag-sdiv.c: New test.
	* gcc.target/bpf/diag-smod.c: New test.
	* gcc.target/bpf/xbpf-sdiv-1.c: New test.
	* gcc.target/bpf/xbpf-smod-1.c: New test.
---
 gcc/config/bpf/bpf.md                      | 20 ++++++++++++++++++++
 gcc/testsuite/gcc.target/bpf/diag-sdiv.c   | 12 ++++++++++++
 gcc/testsuite/gcc.target/bpf/diag-smod.c   | 12 ++++++++++++
 gcc/testsuite/gcc.target/bpf/xbpf-sdiv-1.c | 14 ++++++++++++++
 gcc/testsuite/gcc.target/bpf/xbpf-smod-1.c | 14 ++++++++++++++
 5 files changed, 72 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/bpf/diag-sdiv.c
 create mode 100644 gcc/testsuite/gcc.target/bpf/diag-smod.c
 create mode 100644 gcc/testsuite/gcc.target/bpf/xbpf-sdiv-1.c
 create mode 100644 gcc/testsuite/gcc.target/bpf/xbpf-smod-1.c

diff --git a/gcc/config/bpf/bpf.md b/gcc/config/bpf/bpf.md
index 769d8ea0096..8e7cf508ccf 100644
--- a/gcc/config/bpf/bpf.md
+++ b/gcc/config/bpf/bpf.md
@@ -165,6 +165,16 @@
   "div<msuffix>\t%0,%2"
   [(set_attr "type" "<mtype>")])
 
+;; However, xBPF does provide a signed division operator, sdiv.
+
+(define_insn "div<AM:mode>3"
+  [(set (match_operand:AM 0 "register_operand" "=r,r")
+        (div:AM (match_operand:AM 1 "register_operand" " 0,0")
+                (match_operand:AM 2 "reg_or_imm_operand" "r,I")))]
+  "TARGET_XBPF"
+  "sdiv<msuffix>\t%0,%2"
+  [(set_attr "type" "<mtype>")])
+
 ;;; Modulus
 
 ;; Note that eBPF doesn't provide instructions for signed integer
@@ -178,6 +188,16 @@
   "mod<msuffix>\t%0,%2"
   [(set_attr "type" "<mtype>")])
 
+;; Again, xBPF provides a signed version, smod.
+
+(define_insn "mod<AM:mode>3"
+  [(set (match_operand:AM 0 "register_operand" "=r,r")
+        (mod:AM (match_operand:AM 1 "register_operand" " 0,0")
+                (match_operand:AM 2 "reg_or_imm_operand" "r,I")))]
+  "TARGET_XBPF"
+  "smod<msuffix>\t%0,%2"
+  [(set_attr "type" "<mtype>")])
+
 ;;; Logical AND
 (define_insn "and<AM:mode>3"
   [(set (match_operand:AM 0 "register_operand" "=r,r")
diff --git a/gcc/testsuite/gcc.target/bpf/diag-sdiv.c b/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
new file mode 100644
index 00000000000..db0c494a789
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/diag-sdiv.c
@@ -0,0 +1,12 @@
+/* Verify signed division does not produce 'sdiv' insn in eBPF.  */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+void
+foo ()
+{
+  signed int x = 5;
+  signed int y = 2;
+  signed int z = x / y;
+}
+/* { dg-final { scan-assembler-not "sdiv(32)?\t%r" } } */
diff --git a/gcc/testsuite/gcc.target/bpf/diag-smod.c b/gcc/testsuite/gcc.target/bpf/diag-smod.c
new file mode 100644
index 00000000000..20234ee39cc
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/diag-smod.c
@@ -0,0 +1,12 @@
+/* Verify signed modulo does not produce 'smod' insn in eBPF.  */
+/* { dg-do compile } */
+/* { dg-options "-O0" } */
+
+void
+foo ()
+{
+  signed int x = 5;
+  signed int y = 2;
+  signed int z = x % y;
+}
+/* { dg-final { scan-assembler-not "smod(32)?\t%r" } } */
diff --git a/gcc/testsuite/gcc.target/bpf/xbpf-sdiv-1.c b/gcc/testsuite/gcc.target/bpf/xbpf-sdiv-1.c
new file mode 100644
index 00000000000..f6c5c9e9f1c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/xbpf-sdiv-1.c
@@ -0,0 +1,14 @@
+/* Verify that sdiv instruction is used for xBPF. */
+/* { dg-do compile } */
+/* { dg-options "-O0 -mxbpf" } */
+
+void
+foo ()
+{
+  signed int x = 5;
+  signed int y = 2;
+  signed int z = x / y;
+  signed int w = x / 3;
+}
+
+/* { dg-final { scan-assembler "sdiv(32)?\t%r" } } */
diff --git a/gcc/testsuite/gcc.target/bpf/xbpf-smod-1.c b/gcc/testsuite/gcc.target/bpf/xbpf-smod-1.c
new file mode 100644
index 00000000000..b3e5816b5cf
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/xbpf-smod-1.c
@@ -0,0 +1,14 @@
+/* Verify that smod instruction is used for xBPF. */
+/* { dg-do compile } */
+/* { dg-options "-O0 -mxbpf" } */
+
+void
+foo ()
+{
+  signed int x = 5;
+  signed int y = 2;
+  signed int z = x % y;
+  signed int w = x % 3;
+}
+
+/* { dg-final { scan-assembler "smod(32)?\t%r" } } */
-- 
2.30.2