diff options
Diffstat (limited to 'lib/Target/ARM/ARMSubtarget.cpp')
| -rw-r--r-- | lib/Target/ARM/ARMSubtarget.cpp | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/lib/Target/ARM/ARMSubtarget.cpp b/lib/Target/ARM/ARMSubtarget.cpp index 8653c462f0..9ff0d61481 100644 --- a/lib/Target/ARM/ARMSubtarget.cpp +++ b/lib/Target/ARM/ARMSubtarget.cpp @@ -162,10 +162,23 @@ void ARMSubtarget::resetSubtargetFeatures(StringRef CPU, StringRef FS) { if (!isThumb() || hasThumb2()) PostRAScheduler = true; - // v6+ may or may not support unaligned mem access depending on the system - // configuration. - if (!StrictAlign && hasV6Ops() && isTargetDarwin()) - AllowsUnalignedMem = true; + if (!StrictAlign) { + // Assume pre-ARMv6 doesn't support unaligned accesses. + // + // ARMv6 may or may not support unaligned accesses depending on the + // SCTLR.U bit, which is architecture-specific. We assume ARMv6 + // Darwin targets support unaligned accesses, and others don't. + // + // ARMv7 always has SCTLR.U set to 1, but it has a new SCTLR.A bit + // which raises an alignment fault on unaligned accesses. Linux + // defaults this bit to 0 and handles it as a system-wide (not + // per-process) setting. It is therefore safe to assume that ARMv7+ + // targets support unaligned accesses. + // + // The above behavior is consistent with GCC. + if (hasV7Ops() || (hasV6Ops() && isTargetDarwin())) + AllowsUnalignedMem = true; + } // NEON f32 ops are non-IEEE 754 compliant. Darwin is ok with it by default. uint64_t Bits = getFeatureBits(); |