Implement proper support for `-falign-functions`
This implements support for the previously ignored flag
`-falign-functions`. This allows the frontend to request alignment on
function definitions in the translation unit where they are not
explicitly requested in code. This is compatible with the GCC behaviour
and the ICC behaviour.
The scalar value passed to `-falign-functions` aligns functions to a
power-of-two boundary. If flag is used, the functions are aligned to
16-byte boundaries. If the scalar is specified, it must be an integer
less than or equal to 4096. If the value is not a power-of-two, the
driver will round it up to the nearest power of two.
llvm-svn: 330378
diff --git a/clang/lib/Driver/ToolChains/CommonArgs.cpp b/clang/lib/Driver/ToolChains/CommonArgs.cpp
index 869cf4c..1527238 100644
--- a/clang/lib/Driver/ToolChains/CommonArgs.cpp
+++ b/clang/lib/Driver/ToolChains/CommonArgs.cpp
@@ -1033,6 +1033,40 @@
return std::make_tuple(RelocM, 0U, false);
}
+// `-falign-functions` indicates that the functions should be aligned to a
+// 16-byte boundary.
+//
+// `-falign-functions=1` is the same as `-fno-align-functions`.
+//
+// The scalar `n` in `-falign-functions=n` must be an integral value between
+// [0, 65536]. If the value is not a power-of-two, it will be rounded up to
+// the nearest power-of-two.
+//
+// If we return `0`, the frontend will default to the backend's preferred
+// alignment.
+//
+// NOTE: icc only allows values between [0, 4096]. icc uses `-falign-functions`
+// to mean `-falign-functions=16`. GCC defaults to the backend's preferred
+// alignment. For unaligned functions, we default to the backend's preferred
+// alignment.
+unsigned tools::ParseFunctionAlignment(const ToolChain &TC,
+ const ArgList &Args) {
+ const Arg *A = Args.getLastArg(options::OPT_falign_functions,
+ options::OPT_falign_functions_EQ,
+ options::OPT_fno_align_functions);
+ if (!A || A->getOption().matches(options::OPT_fno_align_functions))
+ return 0;
+
+ if (A->getOption().matches(options::OPT_falign_functions))
+ return 0;
+
+ unsigned Value = 0;
+ if (StringRef(A->getValue()).getAsInteger(10, Value) || Value > 65536)
+ TC.getDriver().Diag(diag::err_drv_invalid_int_value)
+ << A->getAsString(Args) << A->getValue();
+ return Value ? llvm::Log2_32_Ceil(std::min(Value, 65536u)) : Value;
+}
+
void tools::AddAssemblerKPIC(const ToolChain &ToolChain, const ArgList &Args,
ArgStringList &CmdArgs) {
llvm::Reloc::Model RelocationModel;