[llvm-bugs] [Bug 30732] New: neon instructions emitted for targets without it.

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=30732

            Bug ID: 30732
           Summary: neon instructions emitted for targets without it.
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: ARM
          Assignee: unassignedbugs at nondot.org
          Reporter: yyc1992 at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

>From `lib/Target/ARM/ARM.td` it seems that all ARMv7a targets have
`FeatureNEON`. However, this should be an optional feature on armv7-a and for
example the scaleway server uses cortex-a7 without neon instructions.

I initially noticed this in the julia codegen. It can also be reproduced using
clang by compiling `double f(void) { return 0.0; }` with `clang
--target=arm-linux-unknown-gnueabihf -march=armv7-a -mcpu=generic -O2 f.c -S -o
-`. The asm generated has `.fpu    neon` and is using neon instruction
`vmov.i32        d0, #0x0` to construct the return value.

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