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[ARM] Pass subtarget feature "+strict-align". 

This commit changes the driver to save subtarget feature "+strict-align" to the
IR instead of using backend option "arm-strict-align". This is needed for LTO.

Also, move the logic in ARM backend that was deciding whether strict alignment
should be forced to the front-end.

rdar://problem/21529937

http://reviews.llvm.org/D11472

llvm-svn: 243489
This commit is contained in:
Akira Hatanaka 2015-07-28 22:26:45 +00:00
parent fc6eb071ab
commit 7651dd8359
3 changed files with 67 additions and 25 deletions
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57
clang/lib/Driver/Tools.cpp
View File

@ -799,6 +799,42 @@ static void getARMTargetFeatures(const Driver &D, const llvm::Triple &Triple,
Features.push_back("+long-calls");
}
// Kernel code has more strict alignment requirements.
if (KernelOrKext)
Features.push_back("+strict-align");
else if (Arg *A = Args.getLastArg(options::OPT_mno_unaligned_access,
options::OPT_munaligned_access)) {
if (A->getOption().matches(options::OPT_munaligned_access)) {
// No v6M core supports unaligned memory access (v6M ARM ARM A3.2).
if (Triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6m)
D.Diag(diag::err_target_unsupported_unaligned) << "v6m";
} else
Features.push_back("+strict-align");
} else {
// 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 and NetBSD 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+
// Linux targets support unaligned accesses. The same goes for NaCl.
//
// The above behavior is consistent with GCC.
int VersionNum = getARMSubArchVersionNumber(Triple);
if (Triple.isOSDarwin() || Triple.isOSNetBSD()) {
if (VersionNum < 6)
Features.push_back("+strict-align");
} else if (Triple.isOSLinux() || Triple.isOSNaCl()) {
if (VersionNum < 7)
Features.push_back("+strict-align");
} else
Features.push_back("+strict-align");
}
// llvm does not support reserving registers in general. There is support
// for reserving r9 on ARM though (defined as a platform-specific register
// in ARM EABI).
@ -879,27 +915,6 @@ void Clang::AddARMTargetArgs(const ArgList &Args, ArgStringList &CmdArgs,
CmdArgs.push_back("hard");
}
// Kernel code has more strict alignment requirements.
if (KernelOrKext) {
CmdArgs.push_back("-backend-option");
CmdArgs.push_back("-arm-strict-align");
}
// -mkernel implies -mstrict-align; don't add the redundant option.
if (!KernelOrKext) {
if (Arg *A = Args.getLastArg(options::OPT_mno_unaligned_access,
options::OPT_munaligned_access)) {
CmdArgs.push_back("-backend-option");
if (A->getOption().matches(options::OPT_mno_unaligned_access))
CmdArgs.push_back("-arm-strict-align");
else {
if (Triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6m)
D.Diag(diag::err_target_unsupported_unaligned) << "v6m";
CmdArgs.push_back("-arm-no-strict-align");
}
}
}
// Forward the -mglobal-merge option for explicit control over the pass.
if (Arg *A = Args.getLastArg(options::OPT_mglobal_merge,
options::OPT_mno_global_merge)) {

4
clang/test/Driver/apple-kext-mkernel.c
View File

@ -12,8 +12,8 @@
// RUN: FileCheck --check-prefix=CHECK-ARM < %t %s
// CHECK-ARM: "-target-feature" "+long-calls"
// CHECK-ARM: "-backend-option" "-arm-strict-align"
// CHECK-ARM-NOT: "-backend-option" "-arm-strict-align"
// CHECK-ARM: "-target-feature" "+strict-align"
// CHECK-ARM-NOT: "-target-feature" "+strict-align"
// CHECK-ARM: "-fno-builtin"
// CHECK-ARM: "-fno-rtti"
// CHECK-ARM: "-fno-common"

31
clang/test/Driver/arm-alignment.c
View File

@ -7,6 +7,18 @@
// RUN: %clang -target arm-none-gnueabi -mno-unaligned-access -munaligned-access -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM < %t %s
// RUN: %clang -target armv6-apple-darwin -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM < %t %s
// RUN: %clang -target armv6-netbsd-eabi -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM < %t %s
// RUN: %clang -target armv7-unknown-linux -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM < %t %s
// RUN: %clang -target armv7-unknown-nacl-gnueabihf -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-ARM < %t %s
// RUN: %clang -target aarch64-none-gnueabi -munaligned-access -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-AARCH64 < %t %s
@ -16,7 +28,7 @@
// RUN: %clang -target aarch64-none-gnueabi -mno-unaligned-access -munaligned-access -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-UNALIGNED-AARCH64 < %t %s
// CHECK-UNALIGNED-ARM: "-backend-option" "-arm-no-strict-align"
// CHECK-UNALIGNED-ARM-NOT: "-target-feature" "+strict-align"
// CHECK-UNALIGNED-AARCH64: "-backend-option" "-aarch64-no-strict-align"
@ -32,6 +44,21 @@
// RUN: %clang -target arm-none-gnueabi -munaligned-access -mstrict-align -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
// RUN: %clang -target arm-none-gnueabi -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
// RUN: %clang -target armv5-apple-darwin -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
// RUN: %clang -target armv5t-netbsd-eabi -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
// RUN: %clang -target armv6-unknown-linux -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
// RUN: %clang -target armv6-unknown-nacl-gnueabihf -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-ALIGNED-ARM < %t %s
// RUN: %clang -target aarch64-none-gnueabi -mno-unaligned-access -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-ALIGNED-AARCH64 < %t %s
@ -47,7 +74,7 @@
// RUN: %clang -target aarch64-none-gnueabi -mkernel -mno-unaligned-access -### %s 2> %t
// RUN: FileCheck --check-prefix=CHECK-ALIGNED-AARCH64 < %t %s
// CHECK-ALIGNED-ARM: "-backend-option" "-arm-strict-align"
// CHECK-ALIGNED-ARM: "-target-feature" "+strict-align"
// CHECK-ALIGNED-AARCH64: "-backend-option" "-aarch64-strict-align"
// Make sure that v6M cores always trigger the unsupported aligned accesses error