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From: "juntangc at amazon dot com" <sourceware-bugzilla@sourceware.org>
To: glibc-bugs@sourceware.org
Subject: [Bug libc/29330] New: hp-timing not correct for graviton
Date: Thu, 07 Jul 2022 16:42:24 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D29330

            Bug ID: 29330
           Summary: hp-timing not correct for graviton
           Product: glibc
           Version: unspecified
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: juntangc at amazon dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

hp-timing is only used on benchtests today, but it can be used on other thi=
ngs
in the future. It's broken on graviton beacuse the freq we have is 10500000=
00.
1000000000ULL/1050000000ULL =3D 0 and thus benchtests output are all 0.

The following patch can fix the bug:

```
diff --git a/sysdeps/aarch64/hp-timing.h b/sysdeps/aarch64/hp-timing.h
index f7f7ac7cae..270e0c2e24 100644
--- a/sysdeps/aarch64/hp-timing.h
+++ b/sysdeps/aarch64/hp-timing.h
@@ -41,7 +41,7 @@ typedef uint64_t hp_timing_t;
 #define HP_TIMING_DIFF(Diff, Start, End)                       \
 ({  hp_timing_t freq;                                          \
     __asm__ __volatile__ ("mrs %0, cntfrq_el0" : "=3Dr" (freq)); \
-   (Diff) =3D ((End) - (Start)) * (UINT64_C(1000000000) / freq); \
+   (Diff) =3D (hp_timing_t)((End) - (Start)) * ((1000000000.0) / freq);  \
 })

 #endif /* hp-timing.h */
```

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