gcc/0186-LoongArch-Add-support-to-annotate-tablejump.patch

From 5079c41ada379bd8d1bdb92dd2b91e72e9496ea6 Mon Sep 17 00:00:00 2001
From: Xi Ruoyao <xry111@xry111.site>
Date: Thu, 11 Jul 2024 19:43:48 +0800
Subject: [PATCH 186/188] LoongArch: Add support to annotate tablejump

This is per the request from the kernel developers.  For generating the
ORC unwind info, the objtool program needs to analysis the control flow
of a .o file.  If a jump table is used, objtool has to correlate the
jump instruction with the table.

On x86 (where objtool was initially developed) it's simple: a relocation
entry natrually correlates them because one single instruction is used
for table-based jump.  But on an RISC machine objtool would have to
reconstruct the data flow if it must find out the correlation on its
own.

So, emit an additional section to store the correlation info as pairs of
addresses, each pair contains the address of a jump instruction (jr) and
the address of the jump table.  This is very trivial to implement in
GCC.

gcc/ChangeLog:

	* config/loongarch/genopts/loongarch.opt.in
	(mannotate-tablejump): New option.
	* config/loongarch/loongarch.opt: Regenerate.
	* config/loongarch/loongarch.md (tablejump<mode>): Emit
	additional correlation info between the jump instruction and the
	jump table, if -mannotate-tablejump.
	* doc/invoke.texi: Document -mannotate-tablejump.

gcc/testsuite/ChangeLog:

	* gcc.target/loongarch/jump-table-annotate.c: New test.

Suggested-by: Tiezhu Yang <yangtiezhu@loongson.cn>
---
 gcc/config/loongarch/genopts/loongarch.opt.in     |  4 ++++
 gcc/config/loongarch/loongarch.md                 | 12 +++++++++++-
 gcc/config/loongarch/loongarch.opt                |  4 ++++
 gcc/doc/invoke.texi                               | 13 ++++++++++++-
 .../gcc.target/loongarch/jump-table-annotate.c    | 15 +++++++++++++++
 5 files changed, 46 insertions(+), 2 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/loongarch/jump-table-annotate.c

diff --git a/gcc/config/loongarch/genopts/loongarch.opt.in b/gcc/config/loongarch/genopts/loongarch.opt.in
index 0ecd10922..20795f6bd 100644
--- a/gcc/config/loongarch/genopts/loongarch.opt.in
+++ b/gcc/config/loongarch/genopts/loongarch.opt.in
@@ -301,3 +301,7 @@ default value is 4.
 ; CPUCFG independently, so we use bit flags to specify them.
 TargetVariable
 HOST_WIDE_INT la_isa_evolution = 0
+
+mannotate-tablejump
+Target Mask(ANNOTATE_TABLEJUMP) Save
+Annotate table jump instruction (jr {reg}) to correlate it with the jump table.
diff --git a/gcc/config/loongarch/loongarch.md b/gcc/config/loongarch/loongarch.md
index 15960a79f..66236a7c7 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -3496,12 +3496,22 @@
   DONE;
 })
 
+(define_mode_attr mode_size [(DI "8") (SI "4")])
+
 (define_insn "@tablejump<mode>"
   [(set (pc)
 	(match_operand:P 0 "register_operand" "e"))
    (use (label_ref (match_operand 1 "" "")))]
   ""
-  "jr\t%0"
+  {
+    return TARGET_ANNOTATE_TABLEJUMP
+      ? "1:jr\t%0\n\t"
+	".pushsection\t.discard.tablejump_annotate\n\t"
+	"\t.<mode_size>byte\t1b\n\t"
+	"\t.<mode_size>byte\t%1\n\t"
+	".popsection"
+      : "jr\t%0";
+  }
   [(set_attr "type" "jump")
    (set_attr "mode" "none")])
 
diff --git a/gcc/config/loongarch/loongarch.opt b/gcc/config/loongarch/loongarch.opt
index 69b3b965c..16fed6ec3 100644
--- a/gcc/config/loongarch/loongarch.opt
+++ b/gcc/config/loongarch/loongarch.opt
@@ -310,6 +310,10 @@ default value is 4.
 TargetVariable
 HOST_WIDE_INT la_isa_evolution = 0
 
+mannotate-tablejump
+Target Mask(ANNOTATE_TABLEJUMP) Save
+Annotate table jump instruction (jr {reg}) to correlate it with the jump table
+
 mfrecipe
 Target Mask(ISA_FRECIPE) Var(la_isa_evolution)
 Support frecipe.{s/d} and frsqrte.{s/d} instructions.
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index f6d59317b..d2c52cdf4 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1011,7 +1011,7 @@ Objective-C and Objective-C++ Dialects}.
 -mcmodel=@var{code-model} -mrelax -mpass-mrelax-to-as @gol
 -mrecip  -mrecip=@var{opt} -mfrecipe -mno-frecipe -mdiv32 -mno-div32 @gol
 -mlam-bh -mno-lam-bh -mlamcas -mno-lamcas -mld-seq-sa -mno-ld-seq-sa @gol
--mtls-dialect=@var{opt}}
+-mtls-dialect=@var{opt} -mannotate-tablejump -mno-annotate-tablejump}
 
 @emph{M32R/D Options}
 @gccoptlist{-m32r2  -m32rx  -m32r @gol
@@ -24750,6 +24750,17 @@ Whether a load-load barrier (@code{dbar 0x700}) is needed.  When build with
 This option controls which tls dialect may be used for general dynamic and
 local dynamic TLS models.
 
+@opindex mannotate-tablejump
+@opindex mno-annotate-tablejump
+@item -mannotate-tablejump
+@itemx -mno-annotate-tablejump
+Create an annotation section @code{.discard.tablejump_annotate} to
+correlate the @code{jirl} instruction and the jump table when a jump
+table is used to optimize the @code{switch} statement.  Some external
+tools, for example @file{objtool} of the Linux kernel building system,
+need the annotation to analysis the control flow.  The default is
+@option{-mno-annotate-tablejump}.
+
 @table @samp
 @item trad
 Use traditional TLS. This is the default.
diff --git a/gcc/testsuite/gcc.target/loongarch/jump-table-annotate.c b/gcc/testsuite/gcc.target/loongarch/jump-table-annotate.c
new file mode 100644
index 000000000..9d58e60e3
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/jump-table-annotate.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-mannotate-tablejump" } */
+
+extern void asdf(int);
+void foo(int x) {
+  switch (x) {
+  case 0: asdf(10); break;
+  case 1: asdf(11); break;
+  case 2: asdf(12); break;
+  case 3: asdf(13); break;
+  case 4: asdf(14); break;
+  }
+}
+
+/* { dg-final { scan-assembler "\\.discard\\.tablejump_annotate" } } */
-- 
2.43.0