[PATCH 0/3] bpf: add -mcpu and related feature options

[PATCH 0/3] bpf: add -mcpu and related feature options

[David Faust]

New instructions have been added over time to the eBPF ISA, but
previously there has been no good method to select which version to
target in GCC.

This patch adds the following options to the BPF backend:

  -mcpu={v1, v2, v3}
    Select which version of the eBPF ISA to target. This enables or
    disables generation of certain instructions. The default is v3.

  -mjmpext
    Enable extra conditional branch instructions.
    Enabled for CPU v2 and above.

  -mjmp32
    Enable 32-bit jump/branch instructions.
    Enabled for CPU v3 and above.

  -malu32
    Enable 32-bit ALU instructions.
    Enabled for CPU v3 and above.

Negative versions of -mjmpext, -mjmp32, and -malu32 options are also
supported.

David Faust (3):
  bpf: add -mcpu and related feature options
  bpf testsuite: add tests for new feature options
  doc: document BPF -mcpu and related options

 gcc/config/bpf/bpf-opts.h            |  7 ++++
 gcc/config/bpf/bpf-protos.h          |  1 +
 gcc/config/bpf/bpf.c                 | 41 ++++++++++++++++++++
 gcc/config/bpf/bpf.md                | 44 +++++++++++----------
 gcc/config/bpf/bpf.opt               | 29 ++++++++++++++
 gcc/doc/invoke.texi                  | 39 ++++++++++++++++++-
 gcc/testsuite/gcc.target/bpf/alu-1.c | 56 +++++++++++++++++++++++++++
 gcc/testsuite/gcc.target/bpf/jmp-1.c | 57 ++++++++++++++++++++++++++++
 8 files changed, 253 insertions(+), 21 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/bpf/alu-1.c
 create mode 100644 gcc/testsuite/gcc.target/bpf/jmp-1.c

-- 
2.33.0

[PATCH 1/3] bpf: add -mcpu and related feature options

[David Faust]

New instructions have been added over time to the eBPF ISA, but
previously there has been no good method to select which version to
target in GCC.

This patch adds the following options to the BPF backend:

  -mcpu={v1, v2, v3}
    Select which version of the eBPF ISA to target. This enables or
    disables generation of certain instructions. The default is v3.

  -mjmpext
    Enable extra conditional branch instructions.
    Enabled for CPU v2 and above.

  -mjmp32
    Enable 32-bit jump/branch instructions.
    Enabled for CPU v3 and above.

  -malu32
    Enable 32-bit ALU instructions.
    Enabled for CPU v3 and above.

gcc/ChangeLog:
	* config/bpf/bpf-opts.h (bpf_isa_version): New enum.
	* config/bpf/bpf-protos.h (bpf_expand_cbranch): New.
	* config/bpf/bpf.c (bpf_option_override): Handle -mcpu option.
	(bpf_expand_cbranch): New function.
	* config/bpf/bpf.md (AM mode iterator): Conditionalize support for SI
	mode.
	(zero_extendsidi2): Only use mov32 instruction if it is available.
	(SIM mode iterator): Conditionalize support for SI mode.
	(JM mode iterator): New.
	(cbranchdi4): Update name, use new JM iterator. Use bpf_expand_cbranch.
	(*branch_on_di): Update name, use new JM iterator.
	* config/bpf/bpf.opt: (mjmpext): New option.
	(malu32): Likewise.
	(mjmp32): Likewise.
	(mcpu): Likewise.
	(bpf_isa): New enum.
---
 gcc/config/bpf/bpf-opts.h   |  7 ++++++
 gcc/config/bpf/bpf-protos.h |  1 +
 gcc/config/bpf/bpf.c        | 41 ++++++++++++++++++++++++++++++++++
 gcc/config/bpf/bpf.md       | 44 ++++++++++++++++++++-----------------
 gcc/config/bpf/bpf.opt      | 29 ++++++++++++++++++++++++
 5 files changed, 102 insertions(+), 20 deletions(-)

diff --git a/gcc/config/bpf/bpf-opts.h b/gcc/config/bpf/bpf-opts.h
index 1bc930cd194..456e39c2200 100644
--- a/gcc/config/bpf/bpf-opts.h
+++ b/gcc/config/bpf/bpf-opts.h
@@ -53,4 +53,11 @@ enum bpf_kernel_version
   LINUX_NATIVE,
 };
 
+enum bpf_isa_version
+{
+  ISA_V1,
+  ISA_V2,
+  ISA_V3,
+};
+
 #endif /* ! BPF_OPTS_H */
diff --git a/gcc/config/bpf/bpf-protos.h b/gcc/config/bpf/bpf-protos.h
index 7ce3386ffda..e6bb9015449 100644
--- a/gcc/config/bpf/bpf-protos.h
+++ b/gcc/config/bpf/bpf-protos.h
@@ -29,6 +29,7 @@ extern void bpf_print_operand (FILE *, rtx, int);
 extern void bpf_print_operand_address (FILE *, rtx);
 extern void bpf_expand_prologue (void);
 extern void bpf_expand_epilogue (void);
+extern void bpf_expand_cbranch (machine_mode, rtx *);
 
 rtl_opt_pass * make_pass_bpf_core_attr (gcc::context *);
 
diff --git a/gcc/config/bpf/bpf.c b/gcc/config/bpf/bpf.c
index 01d9c03479e..82bb698bd91 100644
--- a/gcc/config/bpf/bpf.c
+++ b/gcc/config/bpf/bpf.c
@@ -242,6 +242,17 @@ bpf_option_override (void)
       target_flags |= MASK_BPF_CORE;
       write_symbols |= BTF_WITH_CORE_DEBUG;
     }
+
+  /* Determine available features from ISA setting (-mcpu=).  */
+  if (bpf_has_jmpext == -1)
+    bpf_has_jmpext = (bpf_isa >= ISA_V2);
+
+  if (bpf_has_alu32 == -1)
+    bpf_has_alu32 = (bpf_isa >= ISA_V3);
+
+  if (bpf_has_jmp32 == -1)
+    bpf_has_jmp32 = (bpf_isa >= ISA_V3);
+
 }
 
 #undef TARGET_OPTION_OVERRIDE
@@ -540,6 +551,36 @@ bpf_expand_epilogue (void)
   emit_jump_insn (gen_exit ());
 }
 
+/* Expand to the instructions for a conditional branch. This function
+   is called when expanding the 'cbranch<mode>4' pattern in bpf.md.  */
+
+void
+bpf_expand_cbranch (machine_mode mode, rtx *operands)
+{
+  /* If all jump instructions are available, nothing special to do here.  */
+  if (bpf_has_jmpext)
+    return;
+
+  enum rtx_code code = GET_CODE (operands[0]);
+
+  /* Without the conditional branch instructions jslt, jsle, jlt, jle, we need
+     to convert conditional branches that would use them to an available
+     operation instead by reversing the comparison.  */
+  if ((code == LT || code == LE || code == LTU || code == LEU))
+    {
+      /* Reverse the condition.  */
+      PUT_CODE (operands[0], reverse_condition (code));
+
+      /* Swap the operands, and ensure that the first is a register.  */
+      if (!register_operand (operands[2], mode))
+	operands[2] = force_reg (mode, operands[2]);
+
+      rtx tmp = operands[1];
+      operands[1] = operands[2];
+      operands[2] = tmp;
+    }
+}
+
 /* Return the initial difference between the specified pair of
    registers.  The registers that can figure in FROM, and TO, are
    specified by ELIMINABLE_REGS in bpf.h.
diff --git a/gcc/config/bpf/bpf.md b/gcc/config/bpf/bpf.md
index 03830cc250e..c8a85d66d08 100644
--- a/gcc/config/bpf/bpf.md
+++ b/gcc/config/bpf/bpf.md
@@ -100,9 +100,9 @@
 ;; insns, with the proper modes.
 ;;
 ;; 32-bit arithmetic (for SI modes) is implemented using the alu32
-;; instructions.
+;; instructions, if available.
 
-(define_mode_iterator AM [SI DI])
+(define_mode_iterator AM [(SI "bpf_has_alu32") DI])
 
 ;;; Addition
 (define_insn "add<AM:mode>3"
@@ -264,7 +264,7 @@
 	  (match_operand:SI 1 "nonimmediate_operand" "r,m")))]
   ""
   "@
-   mov32\t%0,%1
+   * return bpf_has_alu32 ? \"mov32\t%0,%1\" : \"mov\t%0,%1\;and\t%0,0xffffffff\";
    ldxw\t%0,%1"
   [(set_attr "type" "alu,ldx")])
 
@@ -313,7 +313,7 @@
 
 ;;;; Shifts
 
-(define_mode_iterator SIM [SI DI])
+(define_mode_iterator SIM [(SI "bpf_has_alu32") DI])
 
 (define_insn "ashr<SIM:mode>3"
   [(set (match_operand:SIM 0 "register_operand"                 "=r,r")
@@ -344,24 +344,28 @@
 ;; The eBPF jump instructions use 64-bit arithmetic when evaluating
 ;; the jump conditions.  Therefore we use DI modes below.
 
-(define_expand "cbranchdi4"
+(define_mode_iterator JM [(SI "bpf_has_jmp32") DI])
+
+(define_expand "cbranch<JM:mode>4"
   [(set (pc)
 	(if_then_else (match_operator 0 "comparison_operator"
-			[(match_operand:DI 1 "register_operand")
-			 (match_operand:DI 2 "reg_or_imm_operand")])
+			[(match_operand:JM 1 "register_operand")
+			 (match_operand:JM 2 "reg_or_imm_operand")])
 		      (label_ref (match_operand 3 "" ""))
 		      (pc)))]
   ""
 {
   if (!ordered_comparison_operator (operands[0], VOIDmode))
     FAIL;
+
+  bpf_expand_cbranch (<JM:MODE>mode, operands);
 })
 
-(define_insn "*branch_on_di"
+(define_insn "*branch_on_<JM:mode>"
   [(set (pc)
 	(if_then_else (match_operator 3 "ordered_comparison_operator"
-			 [(match_operand:DI 0 "register_operand" "r")
-			  (match_operand:DI 1 "reg_or_imm_operand" "rI")])
+			 [(match_operand:JM 0 "register_operand" "r")
+			  (match_operand:JM 1 "reg_or_imm_operand" "rI")])
 		      (label_ref (match_operand 2 "" ""))
 		      (pc)))]
   ""
@@ -370,16 +374,16 @@
 
   switch (code)
   {
-  case EQ: return "jeq\t%0,%1,%2"; break;
-  case NE: return "jne\t%0,%1,%2"; break;
-  case LT: return "jslt\t%0,%1,%2"; break;
-  case LE: return "jsle\t%0,%1,%2"; break;
-  case GT: return "jsgt\t%0,%1,%2"; break;
-  case GE: return "jsge\t%0,%1,%2"; break;
-  case LTU: return "jlt\t%0,%1,%2"; break;
-  case LEU: return "jle\t%0,%1,%2"; break;
-  case GTU: return "jgt\t%0,%1,%2"; break;
-  case GEU: return "jge\t%0,%1,%2"; break;
+  case EQ: return "jeq<msuffix>\t%0,%1,%2"; break;
+  case NE: return "jne<msuffix>\t%0,%1,%2"; break;
+  case LT: return "jslt<msuffix>\t%0,%1,%2"; break;
+  case LE: return "jsle<msuffix>\t%0,%1,%2"; break;
+  case GT: return "jsgt<msuffix>\t%0,%1,%2"; break;
+  case GE: return "jsge<msuffix>\t%0,%1,%2"; break;
+  case LTU: return "jlt<msuffix>\t%0,%1,%2"; break;
+  case LEU: return "jle<msuffix>\t%0,%1,%2"; break;
+  case GTU: return "jgt<msuffix>\t%0,%1,%2"; break;
+  case GEU: return "jge<msuffix>\t%0,%1,%2"; break;
   default:
     gcc_unreachable ();
     return "";
diff --git a/gcc/config/bpf/bpf.opt b/gcc/config/bpf/bpf.opt
index 4493067b987..e8b728ca69f 100644
--- a/gcc/config/bpf/bpf.opt
+++ b/gcc/config/bpf/bpf.opt
@@ -131,3 +131,32 @@ Set a hard limit for the size of each stack frame, in bytes.
 mco-re
 Target Mask(BPF_CORE)
 Generate all necessary information for BPF Compile Once - Run Everywhere.
+
+; Selecting BPF ISA features and versions
+
+mjmpext
+Target Var(bpf_has_jmpext) Init(-1)
+Enable extra conditional-branch instructions j(s)lt and j(s)le.
+
+malu32
+Target Var(bpf_has_alu32) Init(-1)
+Enable 32-bit ALU instructions.
+
+mjmp32
+Target Var(bpf_has_jmp32) Init(-1)
+Enable 32-bit jump instructions.
+
+mcpu=
+Target RejectNegative Joined Var(bpf_isa) Enum(bpf_isa) Init(ISA_V3)
+
+Enum
+Name(bpf_isa) Type(enum bpf_isa_version)
+
+EnumValue
+Enum(bpf_isa) String(v1) Value(ISA_V1)
+
+EnumValue
+Enum(bpf_isa) String(v2) Value(ISA_V2)
+
+EnumValue
+Enum(bpf_isa) String(v3) Value(ISA_V3)
-- 
2.33.0

[PATCH 2/3] bpf testsuite: add tests for new feature options

[David Faust]

This commit adds tests for the new -mjmpext, -mjmp32 and -malu32 feature
options in the BPF backend.

gcc/testsuite/ChangeLog:
	* gcc.target/bpf/alu-1.c: New test.
	* gcc.target/bpf/jmp-1.c: New test.
---
 gcc/testsuite/gcc.target/bpf/alu-1.c | 56 +++++++++++++++++++++++++++
 gcc/testsuite/gcc.target/bpf/jmp-1.c | 57 ++++++++++++++++++++++++++++
 2 files changed, 113 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/bpf/alu-1.c
 create mode 100644 gcc/testsuite/gcc.target/bpf/jmp-1.c

diff --git a/gcc/testsuite/gcc.target/bpf/alu-1.c b/gcc/testsuite/gcc.target/bpf/alu-1.c
new file mode 100644
index 00000000000..98149305e82
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/alu-1.c
@@ -0,0 +1,56 @@
+/* Ensure 32-bit ALU instructions are not generated if -malu32 is
+   not enabled.  */
+
+/* { dg-do compile } */
+/* { dg-options "-mno-alu32" } */
+
+int foo (int a, int b)
+{
+  a += 1;
+  b += a;
+  b -= 5;
+  a -= a;
+
+  a *= 2;
+  b *= a;
+
+  a |= 0xfafa;
+  b |= a;
+  b &= 0x00ffff00;
+  b &= a;
+
+  a <<= 2;
+  b <<= a;
+  b >>= 5;
+  a >>= b;
+
+  int c = a;
+  int d = 5;
+
+  d ^= a;
+  c ^= 0xe5e5e5e5;
+  c = -c;
+
+  unsigned int x = a;
+  unsigned int y = b;
+  x /= 3;
+  y /= x;
+  x %= 4;
+  y %= x;
+
+  return a + b - c + d - x + y;
+}
+
+/* { dg-final { scan-assembler-times "mov32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "add32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "sub32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "mul32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "div32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "mod32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "neg32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "and32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "or32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "xor32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "rsh32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "lsh32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "arsh32\t0" 0 } } */
diff --git a/gcc/testsuite/gcc.target/bpf/jmp-1.c b/gcc/testsuite/gcc.target/bpf/jmp-1.c
new file mode 100644
index 00000000000..eaf825395ef
--- /dev/null
+++ b/gcc/testsuite/gcc.target/bpf/jmp-1.c
@@ -0,0 +1,57 @@
+/* Ensure jlt, jslt, jle and jsle instructions are not generated if
+   -mjmpext is not enabled, and no 32-bit jump instructions are generated
+   if -mjmp32 is not enabled.  */
+
+/* { dg-do compile } */
+/* { dg-options "-mno-jmpext -mno-jmp32" } */
+
+int foo (int a, int b)
+{
+  if (a == 1)
+    b += 1;
+  if (a != 3)
+    b += 2;
+  if (a > 5)
+    b += 3;
+  if (a >= 7)
+    b += 4;
+  if (a < 9)
+    b += 5;
+  if (a <= 10)
+    b += 6;
+
+  return a + b;
+}
+
+unsigned int bar (unsigned int a, unsigned int b)
+{
+  if (a == 1)
+    b += 1;
+  if (a != 3)
+    b += 2;
+  if (a > 5)
+    b += 3;
+  if (a >= 7)
+    b += 4;
+  if (a < 9)
+    b += 5;
+  if (a <= 10)
+    b += 6;
+
+  return a + b;
+}
+
+/* { dg-final { scan-assembler-times "jlt\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jslt\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jle\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jsle\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jeq32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jne32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jlt32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jgt32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jle32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jge32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jslt32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jsgt32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jsle32\t0" 0 } } */
+/* { dg-final { scan-assembler-times "jsge32\t0" 0 } } */
-- 
2.33.0

[PATCH 3/3] doc: document BPF -mcpu and related options

[David Faust]

This commit adds documentation for the new BPF options -mcpu, -mjmpext,
-mjmp32, and -malu32.

gcc/ChangeLog:
	* doc/invoke.texi: Document BPF -mcpu, -mjmpext, -mjmp32 and -malu32
	options.
---
 gcc/doc/invoke.texi | 39 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index d4b3a66ee4f..66f69cf161f 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -904,7 +904,8 @@ Objective-C and Objective-C++ Dialects}.
 
 @emph{eBPF Options}
 @gccoptlist{-mbig-endian -mlittle-endian -mkernel=@var{version}
--mframe-limit=@var{bytes} -mxbpf -mco-re -mno-co-re}
+-mframe-limit=@var{bytes} -mxbpf -mco-re -mno-co-re
+-mjmpext -mjmp32 -malu32 -mcpu=@var{version}}
 
 @emph{FR30 Options}
 @gccoptlist{-msmall-model  -mno-lsim}
@@ -22636,6 +22637,42 @@ Generate code for a big-endian target.
 @opindex mlittle-endian
 Generate code for a little-endian target.  This is the default.
 
+@item -mjmpext
+@opindex mjmpext
+Enable generation of extra conditional-branch instructions.
+Enabled for CPU v2 and above.
+
+@item -mjmp32
+@opindex mjmp32
+Enable 32-bit jump instructions. Enabled for CPU v3 and above.
+
+@item -malu32
+@opindex malu32
+Enable 32-bit ALU instructions. Enabled for CPU v3 and above.
+
+@item -mcpu=@var{version}
+@opindex mcpu
+This specifies which version of the eBPF ISA to target. Newer versions
+may not be supported by all kernels. The default is @samp{v3}.
+
+Supported values for @var{version} are:
+
+@table @samp
+@item v1
+The first stable eBPF ISA with no special features or extensions.
+
+@item v2
+Supports the jump extensions, as in @option{-mjmpext}.
+
+@item v3
+All features of v2, plus:
+@itemize @minus
+@item 32-bit jump operations, as in @option{-mjmp32}
+@item 32-bit ALU operations, as in @option{-malu32}
+@end itemize
+
+@end table
+
 @item -mco-re
 @opindex mco-re
 Enable BPF Compile Once - Run Everywhere (CO-RE) support. Requires and
-- 
2.33.0

Re: [PATCH 0/3] bpf: add -mcpu and related feature options

[Jose E. Marchesi]

Hi David.

> New instructions have been added over time to the eBPF ISA, but
> previously there has been no good method to select which version to
> target in GCC.
>
> This patch adds the following options to the BPF backend:
>
>   -mcpu={v1, v2, v3}
>     Select which version of the eBPF ISA to target. This enables or
>     disables generation of certain instructions. The default is v3.
>
>   -mjmpext
>     Enable extra conditional branch instructions.
>     Enabled for CPU v2 and above.
>
>   -mjmp32
>     Enable 32-bit jump/branch instructions.
>     Enabled for CPU v3 and above.
>
>   -malu32
>     Enable 32-bit ALU instructions.
>     Enabled for CPU v3 and above.
>
> Negative versions of -mjmpext, -mjmp32, and -malu32 options are also
> supported.

The series is OK.
Thanks!

>
> David Faust (3):
>   bpf: add -mcpu and related feature options
>   bpf testsuite: add tests for new feature options
>   doc: document BPF -mcpu and related options
>
>  gcc/config/bpf/bpf-opts.h            |  7 ++++
>  gcc/config/bpf/bpf-protos.h          |  1 +
>  gcc/config/bpf/bpf.c                 | 41 ++++++++++++++++++++
>  gcc/config/bpf/bpf.md                | 44 +++++++++++----------
>  gcc/config/bpf/bpf.opt               | 29 ++++++++++++++
>  gcc/doc/invoke.texi                  | 39 ++++++++++++++++++-
>  gcc/testsuite/gcc.target/bpf/alu-1.c | 56 +++++++++++++++++++++++++++
>  gcc/testsuite/gcc.target/bpf/jmp-1.c | 57 ++++++++++++++++++++++++++++
>  8 files changed, 253 insertions(+), 21 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/bpf/alu-1.c
>  create mode 100644 gcc/testsuite/gcc.target/bpf/jmp-1.c