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LoongArch: Fix runtime error in a gcc build with --with-build-config=bootstrap-ubsan

Message ID 20231123030556.31356-1-guojie@loongson.cn
State Accepted
Headers
Series LoongArch: Fix runtime error in a gcc build with --with-build-config=bootstrap-ubsan |

Checks

Context Check Description
snail/gcc-patch-check success Github commit url

Commit Message

Guo Jie Nov. 23, 2023, 3:05 a.m. UTC 
  gcc/ChangeLog:

	* config/loongarch/loongarch.cc (loongarch_split_plus_constant):
	avoid left shift of negative value -0x8000.

---
 gcc/config/loongarch/loongarch.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Xi Ruoyao Nov. 23, 2023, 3:31 a.m. UTC | #1 
On Thu, 2023-11-23 at 11:05 +0800, Guo Jie wrote:
> gcc/ChangeLog:
> 
> 	* config/loongarch/loongarch.cc (loongarch_split_plus_constant):
> 	avoid left shift of negative value -0x8000.

> ---
>  gcc/config/loongarch/loongarch.cc | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
> index 33357c670e1..81cd9fa1e7c 100644
> --- a/gcc/config/loongarch/loongarch.cc
> +++ b/gcc/config/loongarch/loongarch.cc
> @@ -4249,7 +4249,7 @@ loongarch_split_plus_constant (rtx *op, machine_mode mode)
>    else if (loongarch_addu16i_imm12_operand_p (v, mode))
>      a = (v & ~HWIT_UC_0xFFF) + ((v & 0x800) << 1);
>    else if (mode == DImode && DUAL_ADDU16I_OPERAND (v))
> -    a = (v > 0 ? 0x7fff : -0x8000) << 16;
> +    a = (v > 0 ? 0x7fff0000 : ~0x7fffffff);

LGTM.

"-0x8000 << 16" is allowed by C++20 [it allows x << 16 as long as x * (1
<< 16) does not overflow], but not C++11.

Unfortunately when I wrote the code I just used the C++20 specification
as a reference...  Thanks for the correction.
chenglulu Nov. 27, 2023, 2:54 a.m. UTC | #2 
Pushed to r14-5864.

在 2023/11/23 上午11:05, Guo Jie 写道:
> gcc/ChangeLog:
>
> 	* config/loongarch/loongarch.cc (loongarch_split_plus_constant):
> 	avoid left shift of negative value -0x8000.
>
> ---
>   gcc/config/loongarch/loongarch.cc | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
> index 33357c670e1..81cd9fa1e7c 100644
> --- a/gcc/config/loongarch/loongarch.cc
> +++ b/gcc/config/loongarch/loongarch.cc
> @@ -4249,7 +4249,7 @@ loongarch_split_plus_constant (rtx *op, machine_mode mode)
>     else if (loongarch_addu16i_imm12_operand_p (v, mode))
>       a = (v & ~HWIT_UC_0xFFF) + ((v & 0x800) << 1);
>     else if (mode == DImode && DUAL_ADDU16I_OPERAND (v))
> -    a = (v > 0 ? 0x7fff : -0x8000) << 16;
> +    a = (v > 0 ? 0x7fff0000 : ~0x7fffffff);
>     else
>       gcc_unreachable ();
>
diff mbox series

Patch

diff --git a/gcc/config/loongarch/loongarch.cc b/gcc/config/loongarch/loongarch.cc
index 33357c670e1..81cd9fa1e7c 100644
--- a/gcc/config/loongarch/loongarch.cc
+++ b/gcc/config/loongarch/loongarch.cc
@@ -4249,7 +4249,7 @@  loongarch_split_plus_constant (rtx *op, machine_mode mode)
   else if (loongarch_addu16i_imm12_operand_p (v, mode))
     a = (v & ~HWIT_UC_0xFFF) + ((v & 0x800) << 1);
   else if (mode == DImode && DUAL_ADDU16I_OPERAND (v))
-    a = (v > 0 ? 0x7fff : -0x8000) << 16;
+    a = (v > 0 ? 0x7fff0000 : ~0x7fffffff);
   else
     gcc_unreachable ();