Expand our own config.guess-like logic in configure, rather than only asking LLVM. We have to decide some things before we get an LLVM to ask.

Makefile.in

@@ -11,7 +11,8 @@ ifneq ($(MAKE_RESTARTS),)
 CFG_INFO := $(info cfg: make restarts: $(MAKE_RESTARTS))
 endif
 
-CFG_INFO := $(info cfg: building on $(CFG_OSTYPE) $(CFG_CPUTYPE))
+CFG_INFO := $(info cfg: shell host triple $(CFG_HOST_TRIPLE))
+CFG_INFO := $(info cfg: llvm host triple $(CFG_LLVM_TRIPLE))
 
 ifdef CFG_DISABLE_OPTIMIZE
   $(info cfg: disabling rustc optimization (CFG_DISABLE_OPTIMIZE))

configure

@@ -127,8 +127,8 @@ need_cmd sed
 msg "inspecting environment"
 
 CFG_OSTYPE=$(uname -s)
-
 CFG_CPUTYPE=$(uname -m)
+
 if [ $CFG_OSTYPE = Darwin -a $CFG_CPUTYPE = i386 ]
 then
     # Darwin's `uname -s` lies and always returns i386. We have to use sysctl
@@ -139,6 +139,54 @@ then
     fi
 fi
 
+
+# The goal here is to come up with the same triple as LLVM would,
+# at least for the subset of platforms we're willing to target.
+
+case $CFG_OSTYPE in
+
+    Linux)
+        CFG_OSTYPE=unknown-linux-gnu
+        ;;
+
+    FreeBSD)
+        CFG_OSTYPE=unknown-freebsd
+        ;;
+
+    Darwin)
+        CFG_OSTYPE=apple-darwin
+        ;;
+
+    MINGW32*)
+        CFG_OSTYPE=pc-mingw32
+        ;;
+
+    *)
+        err "unknown OS type: $CFG_OSTYPE"
+        ;;
+esac
+
+
+case $CFG_CPUTYPE in
+
+    i386 | i486 | i686 | i786 | x86)
+        CFG_CPUTYPE=i686
+        ;;
+
+    xscale | arm)
+        CFG_CPUTYPE=arm
+        ;;
+
+    x86_64 | x86-64 | x64)
+        CFG_CPUTYPE=x86_64
+        ;;
+
+    *)
+        err "unknown CPU type: $CFG_CPUTYPE"
+esac
+
+CFG_HOST_TRIPLE="${CFG_CPUTYPE}-${CFG_OSTYPE}"
+
 CFG_SELF=$(echo $0 | tr '\\' '/')
 CFG_SRC_DIR=${CFG_SELF%${CFG_SELF##*/}}
 CFG_BUILD_DIR=$(echo $PWD | tr '\\' '/')
@@ -180,6 +228,7 @@ putvar CFG_SRC_DIR
 putvar CFG_BUILD_DIR
 putvar CFG_OSTYPE
 putvar CFG_CPUTYPE
+putvar CFG_HOST_TRIPLE
 putvar CFG_CONFIGURE_ARGS
 
 step_msg "looking for build programs"

mk/platform.mk

@@ -7,7 +7,7 @@ CFG_GCCISH_LINK_FLAGS :=
 # embedded into the executable, so use a no-op command.
 CFG_DSYMUTIL := true
 
-ifeq ($(CFG_OSTYPE), FreeBSD)
+ifeq ($(findstring freebsd,$(CFG_OSTYPE)),)
   CFG_LIB_NAME=lib$(1).so
   CFG_GCCISH_CFLAGS += -fPIC -march=i686 -I/usr/local/include
   CFG_GCCISH_LINK_FLAGS += -shared -fPIC -lpthread -lrt
@@ -20,7 +20,7 @@ ifeq ($(CFG_OSTYPE), FreeBSD)
   CFG_DEF_SUFFIX := .bsd.def
 endif
 
-ifeq ($(CFG_OSTYPE), Linux)
+ifneq ($(findstring linux,$(CFG_OSTYPE)),)
   CFG_LIB_NAME=lib$(1).so
   CFG_GCCISH_CFLAGS += -fPIC -march=i686
   CFG_GCCISH_LINK_FLAGS += -shared -fPIC -ldl -lpthread -lrt
@@ -46,7 +46,7 @@ ifeq ($(CFG_OSTYPE), Linux)
   endif
 endif
 
-ifeq ($(CFG_OSTYPE), Darwin)
+ifneq ($(findstring darwin,$(CFG_OSTYPE)),)
   CFG_LIB_NAME=lib$(1).dylib
   CFG_UNIXY := 1
   CFG_LDENV := DYLD_LIBRARY_PATH
@@ -69,7 +69,7 @@ ifeq ($(CFG_OSTYPE), Darwin)
   CFG_DEF_SUFFIX := .darwin.def
 endif
 
-ifneq ($(findstring MINGW,$(CFG_OSTYPE)),)
+ifneq ($(findstring mingw,$(CFG_OSTYPE)),)
   CFG_WINDOWSY := 1
 endif