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| author | Lulu Cheng <chenglulu@loongson.cn> | 2023-06-07 10:21:58 +0800 |
|---|---|---|
| committer | Lulu Cheng <chenglulu@loongson.cn> | 2023-06-15 16:23:42 +0800 |
| commit | ddec24e5abe99033c8d6bbe544b4c2b35a0232f2 (patch) | |
| tree | 1048417dd3564c222b029531f010d1f094e6928a | |
| parent | a58bda46377ba74df9ba2bf0a22111c74a1abae8 (diff) | |
| download | gcc-ddec24e5abe99033c8d6bbe544b4c2b35a0232f2.zip gcc-ddec24e5abe99033c8d6bbe544b4c2b35a0232f2.tar.gz gcc-ddec24e5abe99033c8d6bbe544b4c2b35a0232f2.tar.bz2 | |
LoongArch: Avoid non-returning indirect jumps through $ra [PR110136]
Micro-architecture unconditionally treats a "jr $ra" as "return from subroutine",
hence doing "jr $ra" would interfere with both subroutine return prediction and
the more general indirect branch prediction.
Therefore, a problem like PR110136 can cause a significant increase in branch error
prediction rate and affect performance. The same problem exists with "indirect_jump".
gcc/ChangeLog:
PR target/110136
* config/loongarch/loongarch.md: Modify the register constraints for template
"jumptable" and "indirect_jump" from "r" to "e".
Co-authored-by: Andrew Pinski <apinski@marvell.com>
(cherry picked from commit 5430c86e71927492399129f3df80824c6c334ddf)
| -rw-r--r-- | gcc/config/loongarch/loongarch.md | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/gcc/config/loongarch/loongarch.md b/gcc/config/loongarch/loongarch.md index 8f8412f..a64142c 100644 --- a/gcc/config/loongarch/loongarch.md +++ b/gcc/config/loongarch/loongarch.md @@ -2622,6 +2622,10 @@ } [(set_attr "type" "branch")]) +;; Micro-architecture unconditionally treats a "jr $ra" as "return from subroutine", +;; non-returning indirect jumps through $ra would interfere with both subroutine +;; return prediction and the more general indirect branch prediction. + (define_expand "indirect_jump" [(set (pc) (match_operand 0 "register_operand"))] "" @@ -2632,7 +2636,7 @@ }) (define_insn "@indirect_jump<mode>" - [(set (pc) (match_operand:P 0 "register_operand" "r"))] + [(set (pc) (match_operand:P 0 "register_operand" "e"))] "" "jr\t%0" [(set_attr "type" "jump") @@ -2655,7 +2659,7 @@ (define_insn "@tablejump<mode>" [(set (pc) - (match_operand:P 0 "register_operand" "r")) + (match_operand:P 0 "register_operand" "e")) (use (label_ref (match_operand 1 "" "")))] "" "jr\t%0" |