Notice about lack of SIMD support.

In some cases, when SIMD primitives are used without the -fllvm flag, instead of giving the friendly SIMD vector instructions require the LLVM back-end., GHC crashes with varying messages.

The simplest example is

{-# LANGUAGE MagicHash #-}
module Foo where
import GHC.Prim
data V = V Int8X16#

In 7.8.4 this crashes with

ghc: panic! (the 'impossible' happened)
  (GHC version 7.8.4 for x86_64-unknown-linux):
	Size.intSize W128

According to osa1, in HEAD this still crashes, but with

ghc-stage2: panic! (the 'impossible' happened)
  (GHC version 7.11.20150717 for x86_64-unknown-linux):
        Format.intFormat W128

Trac metadata

Trac field	Value
Version	7.8.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
Test case
Differential revisions
BlockedBy
Related
Blocking
CC
Operating system
Architecture

changed weight to 5

added Tbug Trac import labels

This issue is still present on master. I took a quick look at the problem and I made a patch replacing the panic with a sorry message proposing the usage of -fllvm. Here's what ghc says with my patch:

ghc-stage2: sorry! (unimplemented feature or known bug)
  (GHC version 8.1.20160610 for x86_64-unknown-linux):
	Native code generator cannot produce code for Format.intFormat W128
	Consider using the llvm backend with -fllvm

Is this solution convenient ?

Looks good to me!

mentioned in commit f12fb8ab

changed milestone to %8.0.2

It would likely be worth merging this for 8.0.2.

added 1 deleted label

closed

Merged to ghc-8.0 as c6509496.

Trac metadata

Trac field	Value
Resolution	Unresolved → ResolvedFixed

removed 1 deleted label

added compiler crash label

added Pnormal label