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build system: support wrong target triples with LLVM

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clang/LLVM is a bit more finicky with what target triples it accepts compared
to GCC. However, the GCC target triple is needed to properly locate the C
libraries. In case a locally installed GCC toolchain uses a technically not
fully correct target triple, it might be impossible to build with LLVM.

The solution here is to allow specifying a TARGET_ARCH_LLVM target triple
(which defaults to TARGET_ARCH), which is passed to clang. For locating the
C lib, still TARGET_ARCH is used.
This commit is contained in:
Marian Buschsieweke 2021-02-11 17:11:46 +01:00
parent e8cca1e079
commit 6dcd3bb8ff
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GPG Key ID: 61F64C6599B1539F
1 changed files with 4 additions and 3 deletions
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7
makefiles/toolchain/llvm.inc.mk
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@ -51,15 +51,16 @@ gcc_include_dirs = $(realpath \
) )
ifneq (,$(TARGET_ARCH)) ifneq (,$(TARGET_ARCH))
TARGET_ARCH_LLVM ?= $(TARGET_ARCH)
ifeq (,$(CFLAGS_CPU)) ifeq (,$(CFLAGS_CPU))
$(error CFLAGS_CPU must have been defined to use `llvm`.) $(error CFLAGS_CPU must have been defined to use `llvm`.)
endif endif
# Tell clang to cross compile # Tell clang to cross compile
CFLAGS += -target $(TARGET_ARCH) CFLAGS += -target $(TARGET_ARCH_LLVM)
CXXFLAGS += -target $(TARGET_ARCH) CXXFLAGS += -target $(TARGET_ARCH_LLVM)
# We currently don't use LLVM for linking (see comment above). # We currently don't use LLVM for linking (see comment above).
# LINKFLAGS += -target $(TARGET_ARCH) # LINKFLAGS += -target $(TARGET_ARCH_LLVM)
# Clang on Linux uses GCC's C and C++ headers and libstdc++ (installed with GCC) # Clang on Linux uses GCC's C and C++ headers and libstdc++ (installed with GCC)