gcc-14/0019-LoongArch-Add-support-to-annotate-tablejump.patch

From f0416e6a2af1fb1f2b18a4410e679f25c57c5e9f Mon Sep 17 00:00:00 2001
From: Xi Ruoyao <xry111@xry111.site>
Date: Thu, 11 Jul 2024 19:43:48 +0800
Subject: [PATCH 19/20] 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.target/loongarch/jump-table-annotate.c    | 15 +++++++++++++++
 4 files changed, 34 insertions(+), 1 deletion(-)
 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 d00950cb4..d5bbf01d8 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 f70ca85bf..bd0825002 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 91cb5236a..6a396b539 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/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