Support unaligned load/store on more ARM targets

This patch matches GCC behavior: the code used to only allow unaligned
load/store on ARM for v6+ Darwin, it will now allow unaligned load/store
for v6+ Darwin as well as for v7+ on Linux and NaCl.

The distinction is made because v6 doesn't guarantee support (but LLVM
assumes that Apple controls hardware+kernel and therefore have
conformant v6 CPUs), whereas v7 does provide this guarantee (and
Linux/NaCl behave sanely).

The patch keeps the -arm-strict-align command line option, and adds
-arm-no-strict-align. They behave similarly to GCC's -mstrict-align and
-mnostrict-align.

I originally encountered this discrepancy in FastIsel tests which expect
unaligned load/store generation. Overall this should slightly improve
performance in most cases because of reduced I$ pressure.

llvm-svn: 182175

1 files changed, 2 insertions, 3 deletions

diff --git a/llvm/lib/Target/ARM/ARMSubtarget.h b/llvm/lib/Target/ARM/ARMSubtarget.h
index 038eb76ae1d..d01316511c4 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.h
+++ b/llvm/lib/Target/ARM/ARMSubtarget.h
@@ -270,9 +270,8 @@ public:
 
   bool isTargetIOS() const { return TargetTriple.getOS() == Triple::IOS; }
   bool isTargetDarwin() const { return TargetTriple.isOSDarwin(); }
-  bool isTargetNaCl() const {
-    return TargetTriple.getOS() == Triple::NaCl;
-  }
+  bool isTargetNaCl() const { return TargetTriple.getOS() == Triple::NaCl; }
+  bool isTargetLinux() const { return TargetTriple.getOS() == Triple::Linux; }
   bool isTargetELF() const { return !isTargetDarwin(); }
 
   bool isAPCS_ABI() const { return TargetABI == ARM_ABI_APCS; }