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From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: peter.maydell@linaro.org,
	"Philippe Mathieu-Daudé" <philmd@linaro.org>,
	"Idan Horowitz" <idan.horowitz@gmail.com>
Subject: [PULL v2 05/15] tcg: Mark tcg helpers noinline to avoid an issue with LTO
Date: Mon, 23 Jan 2023 16:04:57 -1000	[thread overview]
Message-ID: <20230124020507.3732200-6-richard.henderson@linaro.org> (raw)
In-Reply-To: <20230124020507.3732200-1-richard.henderson@linaro.org>

Marking helpers __attribute__((noinline)) prevents an issue
with GCC's ipa-split pass under --enable-lto.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1454
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Idan Horowitz <idan.horowitz@gmail.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/exec/helper-proto.h | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/include/exec/helper-proto.h b/include/exec/helper-proto.h
index c4b1bda632..7a3f04b58c 100644
--- a/include/exec/helper-proto.h
+++ b/include/exec/helper-proto.h
@@ -6,34 +6,49 @@
 
 #include "exec/helper-head.h"
 
+/*
+ * Work around an issue with --enable-lto, in which GCC's ipa-split pass
+ * decides to split out the noreturn code paths that raise an exception,
+ * taking the __builtin_return_address() along into the new function,
+ * where it no longer computes a value that returns to TCG generated code.
+ * Despite the name, the noinline attribute affects splitter, so this
+ * prevents the optimization in question.  Given that helpers should not
+ * otherwise be called directly, this should have any other visible effect.
+ *
+ * See https://gitlab.com/qemu-project/qemu/-/issues/1454
+ */
+#define DEF_HELPER_ATTR  __attribute__((noinline))
+
 #define DEF_HELPER_FLAGS_0(name, flags, ret) \
-dh_ctype(ret) HELPER(name) (void);
+dh_ctype(ret) HELPER(name) (void) DEF_HELPER_ATTR;
 
 #define DEF_HELPER_FLAGS_1(name, flags, ret, t1) \
-dh_ctype(ret) HELPER(name) (dh_ctype(t1));
+dh_ctype(ret) HELPER(name) (dh_ctype(t1)) DEF_HELPER_ATTR;
 
 #define DEF_HELPER_FLAGS_2(name, flags, ret, t1, t2) \
-dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2));
+dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2)) DEF_HELPER_ATTR;
 
 #define DEF_HELPER_FLAGS_3(name, flags, ret, t1, t2, t3) \
-dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2), dh_ctype(t3));
+dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2), \
+                            dh_ctype(t3)) DEF_HELPER_ATTR;
 
 #define DEF_HELPER_FLAGS_4(name, flags, ret, t1, t2, t3, t4) \
 dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2), dh_ctype(t3), \
-                                   dh_ctype(t4));
+                            dh_ctype(t4)) DEF_HELPER_ATTR;
 
 #define DEF_HELPER_FLAGS_5(name, flags, ret, t1, t2, t3, t4, t5) \
 dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2), dh_ctype(t3), \
-                            dh_ctype(t4), dh_ctype(t5));
+                            dh_ctype(t4), dh_ctype(t5)) DEF_HELPER_ATTR;
 
 #define DEF_HELPER_FLAGS_6(name, flags, ret, t1, t2, t3, t4, t5, t6) \
 dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2), dh_ctype(t3), \
-                            dh_ctype(t4), dh_ctype(t5), dh_ctype(t6));
+                            dh_ctype(t4), dh_ctype(t5), \
+                            dh_ctype(t6)) DEF_HELPER_ATTR;
 
 #define DEF_HELPER_FLAGS_7(name, flags, ret, t1, t2, t3, t4, t5, t6, t7) \
 dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2), dh_ctype(t3), \
                             dh_ctype(t4), dh_ctype(t5), dh_ctype(t6), \
-                            dh_ctype(t7));
+                            dh_ctype(t7)) DEF_HELPER_ATTR;
 
 #define IN_HELPER_PROTO
 
@@ -51,5 +66,6 @@ dh_ctype(ret) HELPER(name) (dh_ctype(t1), dh_ctype(t2), dh_ctype(t3), \
 #undef DEF_HELPER_FLAGS_5
 #undef DEF_HELPER_FLAGS_6
 #undef DEF_HELPER_FLAGS_7
+#undef DEF_HELPER_ATTR
 
 #endif /* HELPER_PROTO_H */
-- 
2.34.1



  parent reply	other threads:[~2023-01-24  2:06 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-24  2:04 [PULL v2 00/15] tcg patch queue Richard Henderson
2023-01-24  2:04 ` [PULL v2 01/15] tcg: Avoid recursion in tcg_gen_mulu2_i32 Richard Henderson
2023-01-24  2:04 ` [PULL v2 02/15] tcg/arm: Use register pair allocation for qemu_{ld, st}_i64 Richard Henderson
2023-01-24  2:04 ` [PULL v2 03/15] common-user/host/ppc: Implement safe-syscall.inc.S Richard Henderson
2023-01-24  2:04 ` [PULL v2 04/15] linux-user: Implment host/ppc/host-signal.h Richard Henderson
2023-01-24  2:04 ` Richard Henderson [this message]
2023-01-24  2:04 ` [PULL v2 06/15] target/loongarch: Enable the disassembler for host tcg Richard Henderson
2023-01-24  2:04 ` [PULL v2 07/15] target/loongarch: Disassemble jirl properly Richard Henderson
2023-01-24  2:05 ` [PULL v2 08/15] target/loongarch: Disassemble pcadd* addresses Richard Henderson
2023-01-24  2:05 ` [PULL v2 09/15] tcg/loongarch64: Optimize immediate loading Richard Henderson
2023-01-24  2:05 ` [PULL v2 10/15] tcg/loongarch64: Update tcg-insn-defs.c.inc Richard Henderson
2023-01-24  2:05 ` [PULL v2 11/15] tcg/loongarch64: Introduce tcg_out_addi Richard Henderson
2023-01-24  2:05 ` [PULL v2 12/15] tcg/loongarch64: Improve setcond expansion Richard Henderson
2023-01-24  2:05 ` [PULL v2 13/15] tcg/loongarch64: Implement movcond Richard Henderson
2023-01-24  2:05 ` [PULL v2 14/15] tcg/loongarch64: Use tcg_pcrel_diff in tcg_out_ldst Richard Henderson
2023-01-24  2:05 ` [PULL v2 15/15] tcg/loongarch64: Reorg goto_tb implementation Richard Henderson
2023-02-03 12:42 ` [PULL v2 00/15] tcg patch queue Peter Maydell

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