In some applications (notably the Linux kernel), "break 0" is used as a
trap that a handler may be able to recover. But in GCC the "trap"
pattern is meant to make the program rightfully die instead.
As [1] describes, sometimes it's vital to distinguish between the two
cases. The kernel developers prefer "break 1" here, but in the
user-space it's better to trigger a SIGILL instead of SIGTRAP as the
latter is more likely used as a application-defined trap.
To support both cases, make the code generation configurable with a new
option.
[1]:https://lore.kernel.org/[email protected]
gcc/
* config/loongarch/genopts/loongarch.opt.in (-mbreak-code=):
New.
* config/loongarch/loongarch.opt: Regenerate.
* config/loongarch/loongarch.md (trap): Separate to a
define_insn and a define_expand which takes la_break_code.
* doc/invoke.texi (-mbreak-code=): Document.
* config/loongarch/loongarch.opt.urls: Regenerate.
gcc/testsuite
* gcc.target/loongarch/trap-default.c: New test.
* gcc.target/loongarch/trap-1.c: New test.
---
gcc/config/loongarch/genopts/loongarch.opt.in | 4 ++++
gcc/config/loongarch/loongarch.md | 14 +++++++++++---
gcc/config/loongarch/loongarch.opt | 4 ++++
gcc/config/loongarch/loongarch.opt.urls | 3 +++
gcc/doc/invoke.texi | 13 ++++++++++++-
gcc/testsuite/gcc.target/loongarch/trap-1.c | 9 +++++++++
gcc/testsuite/gcc.target/loongarch/trap-default.c | 9 +++++++++
7 files changed, 52 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/loongarch/trap-1.c
create mode 100644 gcc/testsuite/gcc.target/loongarch/trap-default.c
diff --git a/gcc/config/loongarch/genopts/loongarch.opt.in
b/gcc/config/loongarch/genopts/loongarch.opt.in
index 39c1545e540..f0c089a928e 100644
--- a/gcc/config/loongarch/genopts/loongarch.opt.in
+++ b/gcc/config/loongarch/genopts/loongarch.opt.in
@@ -205,6 +205,10 @@ mmax-inline-memcpy-size=
Target Joined RejectNegative UInteger Var(la_max_inline_memcpy_size)
Init(1024) Save
-mmax-inline-memcpy-size=SIZE Set the max size of memcpy to inline, default
is 1024.
+mbreak-code=
+Target Joined UInteger Var(la_break_code) Init(-1) Save
+-mbreak-code=CODE Use 'break CODE' for traps supposed to be
unrecoverable, or an 'amswap.w' instruction leading to INE if CODE is out of
range.
+
Enum
Name(explicit_relocs) Type(int)
The code model option names for -mexplicit-relocs:
diff --git a/gcc/config/loongarch/loongarch.md
b/gcc/config/loongarch/loongarch.md
index a275a2d0158..025c86ecd62 100644
--- a/gcc/config/loongarch/loongarch.md
+++ b/gcc/config/loongarch/loongarch.md
@@ -679,14 +679,22 @@ (define_expand "<optab><mode>3"
;; ....................
;;
-(define_insn "trap"
- [(trap_if (const_int 1) (const_int 0))]
+(define_insn "*trap"
+ [(trap_if (const_int 1) (match_operand 0 "const_int_operand"))]
""
{
- return "break\t0";
+ return (const_uimm15_operand (operands[0], VOIDmode)
+ ? "break\t%0"
+ : "amswap.w\t$r0,$r1,$r0");
}
[(set_attr "type" "trap")])
+(define_expand "trap"
+ [(trap_if (const_int 1) (match_dup 0))]
+ ""
+{
+ operands[0] = GEN_INT (la_break_code);
+})
;;
diff --git a/gcc/config/loongarch/loongarch.opt
b/gcc/config/loongarch/loongarch.opt
index fbe61c0bf7c..628eabe8d59 100644
--- a/gcc/config/loongarch/loongarch.opt
+++ b/gcc/config/loongarch/loongarch.opt
@@ -213,6 +213,10 @@ mmax-inline-memcpy-size=
Target Joined RejectNegative UInteger Var(la_max_inline_memcpy_size)
Init(1024) Save
-mmax-inline-memcpy-size=SIZE Set the max size of memcpy to inline, default
is 1024.
+mbreak-code=
+Target Joined UInteger Var(la_break_code) Init(-1) Save
+-mbreak-code=CODE Use 'break CODE' for traps supposed to be
unrecoverable, or an 'amswap.w' instruction leading to INE if CODE is out of
range.
+
Enum
Name(explicit_relocs) Type(int)
The code model option names for -mexplicit-relocs:
diff --git a/gcc/config/loongarch/loongarch.opt.urls
b/gcc/config/loongarch/loongarch.opt.urls
index 606a211f322..c93f04683e1 100644
--- a/gcc/config/loongarch/loongarch.opt.urls
+++ b/gcc/config/loongarch/loongarch.opt.urls
@@ -48,6 +48,9 @@ UrlSuffix(gcc/LoongArch-Options.html#index-mstrict-align-1)
mmax-inline-memcpy-size=
UrlSuffix(gcc/LoongArch-Options.html#index-mmax-inline-memcpy-size)
+mbreak-code=
+UrlSuffix(gcc/LoongArch-Options.html#index-mbreak-code)
+
mexplicit-relocs=
UrlSuffix(gcc/LoongArch-Options.html#index-mexplicit-relocs-1)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 6bd51289dcd..9dcf06cd6c8 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1096,7 +1096,7 @@ Objective-C and Objective-C++ Dialects}.
-mfpu=@var{fpu-type} -msimd=@var{simd-type}
-msoft-float -msingle-float -mdouble-float -mlsx -mno-lsx -mlasx -mno-lasx
-mbranch-cost=@var{n} -maddr-reg-reg-cost=@var{n} -mcheck-zero-division
--mno-check-zero-division
+-mno-check-zero-division -mbreak-code=@var{code}
-mcond-move-int -mno-cond-move-int
-mcond-move-float -mno-cond-move-float
-memcpy -mno-memcpy -mstrict-align -mno-strict-align -G @var{num}
@@ -28439,6 +28439,17 @@ Trap (do not trap) on integer division by zero. The
default is
@option{-mcheck-zero-division} for @option{-O0} or @option{-Og}, and
@option{-mno-check-zero-division} for other optimization levels.
+@opindex mbreak-code
+@item -mbreak-code=@var{code}
+Emit a @code{break} @var{code} instruction for irrecoverable traps
+from @code{__builtin_trap} or inserted by the compiler (for example
+an erroneous path isolated with
+@option{-fisolate-erroneous-paths-dereference}), or an
+@code{amswap.w $r0, $r1, $r0} instruction which will cause the hardware
+to trigger an Instruction Not-defined Exception if @var{code} is negative
+or greater than 32767. The default is -1, meaning to use the
+@code{amswap.w} instruction.
+
@opindex mcond-move-int
@item -mcond-move-int
@itemx -mno-cond-move-int
diff --git a/gcc/testsuite/gcc.target/loongarch/trap-1.c
b/gcc/testsuite/gcc.target/loongarch/trap-1.c
new file mode 100644
index 00000000000..8936f60cce2
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/trap-1.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -w -fisolate-erroneous-paths-dereference -mbreak-code=1"
} */
+/* { dg-final { scan-assembler "break\\t1" } } */
+
+int
+bug (void)
+{
+ return *(int *)0;
+}
diff --git a/gcc/testsuite/gcc.target/loongarch/trap-default.c
b/gcc/testsuite/gcc.target/loongarch/trap-default.c
new file mode 100644
index 00000000000..32948d4c822
--- /dev/null
+++ b/gcc/testsuite/gcc.target/loongarch/trap-default.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -w -fisolate-erroneous-paths-dereference" } */
+/* { dg-final { scan-assembler "amswap\\.w\\t\\\$r0,\\\$r1,\\\$r0" } } */
+
+int
+bug (void)
+{
+ return *(int *)0;
+}
