[clang][driver] Support option '-mcpu' on target AVR.

[benshi001]

Summary

The options '-mcpu' and '-mmcu' has the same functionality except
'-mmcu' is used only for target AVR and MSP430. I think newer AVR
projects should use clang common style options instead of older
avr-gcc style.

Currently we keep '-mmcu' for compatibility with avr-gcc,
and '-mcpu' is superior to '-mmcu'.

[benshi001]

clang/test/Driver/avr-mmcu.c

48

These 4 tests are redundant with their previous lines, so they should be removed.

[arichardson]

clang/lib/Driver/ToolChains/CommonArgs.cpp

387

It looks to me that -mcpu will always take precedence over -mmcu with this code even if mmcu comes later in the command line. Wouldn't it make more sense to treat them as aliases?

[benshi001]

clang/lib/Driver/ToolChains/CommonArgs.cpp

387

That's really a good idea. Thanks!

[MaskRay]

This makes -mmcu= available for non-AVR targets, which is not right.
Even for AVR, if this is a plain alias, is this really necessary? Usually having more than one aliases for one functionality just create confusion as users don't know which one is the canonical.
I think one choice is for AVR users to migrate -mmcu= (if any) to -mcpu=, if there are a significant number of uses. Making a project buildable with Clang usually requires porting efforts, and this request may not be unreasonable.

[benshi001]

In D139305#3974946, @MaskRay wrote:

This makes -mmcu= available for non-AVR targets, which is not right.
Even for AVR, if this is a plain alias, is this really necessary? Usually having more than one aliases for one functionality just create confusion as users don't know which one is the canonical.
I think one choice is for AVR users to migrate -mmcu= (if any) to -mcpu=, if there are a significant number of uses. Making a project buildable with Clang usually requires porting efforts, and this request may not be unreasonable.

I have changed to

1. Both '-mcpu' and '-mmcu' are supported for AVR, and '-mmcu' is not available to others;
2. '-mcpu' is superior to '-mmcu', and '-mcpu' is encouraged for newer clang built AVR projects;
3. A warning will emit if both are specified.

[MaskRay]

I think newr AVR projects should use clang common style options instead of older avr-gcc style.

Does GCC prefer -mcpu= as well? If not, raise a PR there? This seems like a decision we should not unilaterally make on llvm-project side: it's certainly something GCC cares about as well.

[aykevl]

I think having -mcpu as an alias for -mmcu on AVR is fine, but I don't think it's very useful to be honest. The -mmcu (or -mcpu) flag is inherently specific to that particular chip anyway so compatibility is not an issue. In fact, having two flags may even introduce noise and confusion.
I wouldn't be opposed to it though if there is demand for it.

In D139305#3987969, @MaskRay wrote:

Does GCC prefer -mcpu= as well? If not, raise a PR there? This seems like a decision we should not unilaterally make on llvm-project side: it's certainly something GCC cares about as well.

I guess, but avr-gcc is already barely maintained. Most people use an older version (like 5.2.0) because the newer versions produce absolutely terrible code. So I don't think it matters much.

[benshi001]

In D139305#4013217, @aykevl wrote:

I think having -mcpu as an alias for -mmcu on AVR is fine, but I don't think it's very useful to be honest. The -mmcu (or -mcpu) flag is inherently specific to that particular chip anyway so compatibility is not an issue. In fact, having two flags may even introduce noise and confusion.
I wouldn't be opposed to it though if there is demand for it.

In D139305#3987969, @MaskRay wrote:

Does GCC prefer -mcpu= as well? If not, raise a PR there? This seems like a decision we should not unilaterally make on llvm-project side: it's certainly something GCC cares about as well.

I guess, but avr-gcc is already barely maintained. Most people use an older version (like 5.2.0) because the newer versions produce absolutely terrible code. So I don't think it matters much.

I see. Thanks.

clang/include/clang/Driver/Options.td

 def mwindows : Joined<["-"], "mwindows">, Group<m_Group>, Flags<[NoXarchOption]>;
 def mdll : Joined<["-"], "mdll">, Group<m_Group>, Flags<[NoXarchOption]>;
 def municode : Joined<["-"], "municode">, Group<m_Group>, Flags<[NoXarchOption]>;
 def mthreads : Joined<["-"], "mthreads">, Group<m_Group>, Flags<[NoXarchOption]>;
 def mguard_EQ : Joined<["-"], "mguard=">, Group<m_Group>, Flags<[NoXarchOption]>,
   HelpText<"Enable or disable Control Flow Guard checks and guard tables emission">,
   Values<"none,cf,cf-nochecks">;
 def mcpu_EQ : Joined<["-"], "mcpu=">, Group<m_Group>;
-def mmcu_EQ : Joined<["-"], "mmcu=">, Group<m_Group>;
+def mmcu_EQ : Joined<["-"], "mmcu=">, Group<m_Group>, Alias<mcpu_EQ>;
 def msim : Flag<["-"], "msim">, Group<m_Group>;
 def mdynamic_no_pic : Joined<["-"], "mdynamic-no-pic">, Group<m_Group>;
 def mfix_and_continue : Flag<["-"], "mfix-and-continue">, Group<clang_ignored_m_Group>;
 def mieee_fp : Flag<["-"], "mieee-fp">, Group<clang_ignored_m_Group>;
 def minline_all_stringops : Flag<["-"], "minline-all-stringops">, Group<clang_ignored_m_Group>;
 def mno_inline_all_stringops : Flag<["-"], "mno-inline-all-stringops">, Group<clang_ignored_m_Group>;
 def malign_double : Flag<["-"], "malign-double">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"Align doubles to two words in structs (x86 only)">,

clang/lib/Driver/ToolChains/CommonArgs.cpp

std::string tools::getCPUName(const Driver &D, const ArgList &Args,
   case llvm::Triple::thumb:
   case llvm::Triple::thumbeb: {
     StringRef MArch, MCPU;
     arm::getARMArchCPUFromArgs(Args, MArch, MCPU, FromAs);
     return arm::getARMTargetCPU(MCPU, MArch, T);
   }
 
   case llvm::Triple::avr:
-    if (const Arg *A = Args.getLastArg(options::OPT_mmcu_EQ))
+    if (const Arg *A = Args.getLastArg(options::OPT_mcpu_EQ))
       return A->getValue();
     return "";
 
   case llvm::Triple::m68k:
     return m68k::getM68kTargetCPU(Args);
 
   case llvm::Triple::mips:
   case llvm::Triple::mipsel:
   case llvm::Triple::mips64:
   case llvm::Triple::mips64el: {

clang/lib/Driver/ToolChains/MSP430.cpp

 #define MSP430_MCU_FEAT(NAME, HWMULT) .Case(NAME, HWMULT)
 #include "clang/Basic/MSP430Target.def"
       .Default("none");
 }
 
 static StringRef getHWMultLib(const ArgList &Args) {
   StringRef HWMult = Args.getLastArgValue(options::OPT_mhwmult_EQ, "auto");
   if (HWMult == "auto") {
-    HWMult = getSupportedHWMult(Args.getLastArg(options::OPT_mmcu_EQ));
+    HWMult = getSupportedHWMult(Args.getLastArg(options::OPT_mcpu_EQ));
   }
 
   return llvm::StringSwitch<StringRef>(HWMult)
       .Case("16bit", "-lmul_16")
       .Case("32bit", "-lmul_32")
       .Case("f5series", "-lmul_f5")
       .Default("-lmul_none");
 }
 
 void msp430::getMSP430TargetFeatures(const Driver &D, const ArgList &Args,
                                      std::vector<StringRef> &Features) {
-  const Arg *MCU = Args.getLastArg(options::OPT_mmcu_EQ);
+  const Arg *MCU = Args.getLastArg(options::OPT_mcpu_EQ);
   if (MCU && !isSupportedMCU(MCU->getValue())) {
     D.Diag(diag::err_drv_clang_unsupported) << MCU->getValue();
     return;
   }
 
   const Arg *HWMultArg = Args.getLastArg(options::OPT_mhwmult_EQ);
   if (!MCU && !HWMultArg)
     return;
void MSP430ToolChain::AddClangSystemIncludeArgs(const ArgList &DriverArgs,
   addSystemInclude(DriverArgs, CC1Args, Dir.str());
 }
 
 void MSP430ToolChain::addClangTargetOptions(const ArgList &DriverArgs,
                                             ArgStringList &CC1Args,
                                             Action::OffloadKind) const {
   CC1Args.push_back("-nostdsysteminc");
 
-  const auto *MCUArg = DriverArgs.getLastArg(options::OPT_mmcu_EQ);
+  const auto *MCUArg = DriverArgs.getLastArg(options::OPT_mcpu_EQ);
   if (!MCUArg)
     return;
 
   const StringRef MCU = MCUArg->getValue();
   if (MCU.startswith("msp430i")) {
     // 'i' should be in lower case as it's defined in TI MSP430-GCC headers
     CC1Args.push_back(DriverArgs.MakeArgString(
         "-D__MSP430i" + MCU.drop_front(7).upper() + "__"));
static void AddImplicitLinkerScript(const std::string SysRoot,
   if (Args.hasArg(options::OPT_T))
     return;
 
   if (Args.hasArg(options::OPT_msim)) {
     CmdArgs.push_back("-Tmsp430-sim.ld");
     return;
   }
 
-  const Arg *MCUArg = Args.getLastArg(options::OPT_mmcu_EQ);
+  const Arg *MCUArg = Args.getLastArg(options::OPT_mcpu_EQ);
   if (!MCUArg)
     return;
 
   SmallString<128> MCULinkerScriptPath(SysRoot);
   llvm::sys::path::append(MCULinkerScriptPath, "include");
   // -L because <mcu>.ld INCLUDEs <mcu>_symbols.ld
   CmdArgs.push_back(Args.MakeArgString("-L" + MCULinkerScriptPath));
   CmdArgs.push_back(

clang/test/Driver/avr-mmcu.c

-// A test for the propagation of the -mmcu option to -cc1 and -cc1as
+// A test for the propagation of the -mmcu/-mcpu option to -cc1 and -cc1as
 
 // RUN: %clang -### --target=avr -mmcu=attiny11 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK0 %s
+// RUN: %clang -### --target=avr -mcpu=attiny11 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK0 %s
 // CHECK0: "-cc1" {{.*}} "-target-cpu" "attiny11"
 // CHECK0: "-cc1as" {{.*}} "-target-cpu" "attiny11"
 
 // RUN: %clang -### --target=avr -mmcu=at90s2313 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK1 %s
+// RUN: %clang -### --target=avr -mcpu=at90s2313 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK1 %s
 // CHECK1: "-cc1" {{.*}} "-target-cpu" "at90s2313"
 // CHECK1: "-cc1as" {{.*}} "-target-cpu" "at90s2313"
 
 // RUN: %clang -### --target=avr -mmcu=at90s8515 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK2 %s
+// RUN: %clang -### --target=avr -mcpu=at90s8515 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK2 %s
 // CHECK2: "-cc1" {{.*}} "-target-cpu" "at90s8515"
 // CHECK2: "-cc1as" {{.*}} "-target-cpu" "at90s8515"
 
 // RUN: %clang -### --target=avr -mmcu=attiny13a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK3 %s
+// RUN: %clang -### --target=avr -mcpu=attiny13a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK3 %s
 // CHECK3: "-cc1" {{.*}} "-target-cpu" "attiny13a"
 // CHECK3: "-cc1as" {{.*}} "-target-cpu" "attiny13a"
 
 // RUN: %clang -### --target=avr -mmcu=attiny88 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK4 %s
+// RUN: %clang -### --target=avr -mcpu=attiny88 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK4 %s
 // CHECK4: "-cc1" {{.*}} "-target-cpu" "attiny88"
 // CHECK4: "-cc1as" {{.*}} "-target-cpu" "attiny88"
 
-// RUN: %clang -### --target=avr -mmcu=attiny88 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK5 %s
-// CHECK5: "-cc1" {{.*}} "-target-cpu" "attiny88"
-// CHECK5: "-cc1as" {{.*}} "-target-cpu" "attiny88"
-
 // RUN: %clang -### --target=avr -mmcu=atmega8u2 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK6 %s
+// RUN: %clang -### --target=avr -mcpu=atmega8u2 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK6 %s
 // CHECK6: "-cc1" {{.*}} "-target-cpu" "atmega8u2"
 // CHECK6: "-cc1as" {{.*}} "-target-cpu" "atmega8u2"
 
-// RUN: %clang -### --target=avr -mmcu=atmega8u2 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK7 %s
-// CHECK7: "-cc1" {{.*}} "-target-cpu" "atmega8u2"
-// CHECK7: "-cc1as" {{.*}} "-target-cpu" "atmega8u2"
-
 // RUN: %clang -### --target=avr -mmcu=atmega8a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK8 %s
+// RUN: %clang -### --target=avr -mcpu=atmega8a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK8 %s
 // CHECK8: "-cc1" {{.*}} "-target-cpu" "atmega8a"
 // CHECK8: "-cc1as" {{.*}} "-target-cpu" "atmega8a"
 
-// RUN: %clang -### --target=avr -mmcu=atmega8a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECK9 %s
-// CHECK9: "-cc1" {{.*}} "-target-cpu" "atmega8a"
-// CHECK9: "-cc1as" {{.*}} "-target-cpu" "atmega8a"
-
 // RUN: %clang -### --target=avr -mmcu=atmega16a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKa %s
+// RUN: %clang -### --target=avr -mcpu=atmega16a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKa %s
 // CHECKa: "-cc1" {{.*}} "-target-cpu" "atmega16a"
 // CHECKa: "-cc1as" {{.*}} "-target-cpu" "atmega16a"
 
-// RUN: %clang -### --target=avr -mmcu=atmega16a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKb %s
-// CHECKb: "-cc1" {{.*}} "-target-cpu" "atmega16a"
-// CHECKb: "-cc1as" {{.*}} "-target-cpu" "atmega16a"
-
 // RUN: %clang -### --target=avr -mmcu=atmega128a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKc %s
+// RUN: %clang -### --target=avr -mcpu=atmega128a -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKc %s
 // CHECKc: "-cc1" {{.*}} "-target-cpu" "atmega128a"
 // CHECKc: "-cc1as" {{.*}} "-target-cpu" "atmega128a"
 
 // RUN: %clang -### --target=avr -mmcu=atmega2560 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKd %s
+// RUN: %clang -### --target=avr -mcpu=atmega2560 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKd %s
 // CHECKd: "-cc1" {{.*}} "-target-cpu" "atmega2560"
 // CHECKd: "-cc1as" {{.*}} "-target-cpu" "atmega2560"
 
 // RUN: %clang -### --target=avr -mmcu=attiny10 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKe %s
+// RUN: %clang -### --target=avr -mcpu=attiny10 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKe %s
 // CHECKe: "-cc1" {{.*}} "-target-cpu" "attiny10"
 // CHECKe: "-cc1as" {{.*}} "-target-cpu" "attiny10"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega16a4 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKf %s
+// RUN: %clang -### --target=avr -mcpu=atxmega16a4 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKf %s
 // CHECKf: "-cc1" {{.*}} "-target-cpu" "atxmega16a4"
 // CHECKf: "-cc1as" {{.*}} "-target-cpu" "atxmega16a4"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega64b1 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKg %s
+// RUN: %clang -### --target=avr -mcpu=atxmega64b1 -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKg %s
 // CHECKg: "-cc1" {{.*}} "-target-cpu" "atxmega64b1"
 // CHECKg: "-cc1as" {{.*}} "-target-cpu" "atxmega64b1"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega64a1u -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKh %s
+// RUN: %clang -### --target=avr -mcpu=atxmega64a1u -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKh %s
 // CHECKh: "-cc1" {{.*}} "-target-cpu" "atxmega64a1u"
 // CHECKh: "-cc1as" {{.*}} "-target-cpu" "atxmega64a1u"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega128a3u -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKj %s
+// RUN: %clang -### --target=avr -mcpu=atxmega128a3u -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKj %s
 // CHECKj: "-cc1" {{.*}} "-target-cpu" "atxmega128a3u"
 // CHECKj: "-cc1as" {{.*}} "-target-cpu" "atxmega128a3u"
 
 // RUN: %clang -### --target=avr -mmcu=atxmega128a4u -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKi %s
+// RUN: %clang -### --target=avr -mcpu=atxmega128a4u -save-temps %s 2>&1 | FileCheck -check-prefix=CHECKi %s
 // CHECKi: "-cc1" {{.*}} "-target-cpu" "atxmega128a4u"
 // CHECKi: "-cc1as" {{.*}} "-target-cpu" "atxmega128a4u"

clang/test/Driver/msp430-toolchain.c

 // LIBS-NO-STD-NEG-NOT: "--start-group"
 // LIBS-NO-STD-NEG-NOT: "--end-group"
 
 // Test for linker script autodiscovery
 
 // RUN: %clang -### %s --target=msp430 -mmcu=msp430g2553 \
 // RUN:   --sysroot=%S/Inputs/basic_msp430_tree 2>&1 \
 // RUN:   | FileCheck -check-prefix=LD-SCRIPT %s
+// RUN: %clang -### %s --target=msp430 -mcpu=msp430g2553 \
+// RUN:   --sysroot=%S/Inputs/basic_msp430_tree 2>&1 \
+// RUN:   | FileCheck -check-prefix=LD-SCRIPT %s
 // LD-SCRIPT: "{{.*}}/Inputs/basic_msp430_tree/lib/gcc/msp430-elf/8.3.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}msp430-elf-ld"
 // LD-SCRIPT: "-L{{.*}}/Inputs/basic_msp430_tree{{/|\\\\}}include"
 // LD-SCRIPT: "-Tmsp430g2553.ld"
 
 // RUN: %clang -### %s --target=msp430 -mmcu=msp430g2553 \
 // RUN:   --sysroot=%S/Inputs/basic_msp430_tree \
 // RUN:   -T custom_script.ld 2>&1 \
 // RUN:   | FileCheck -check-prefix=CUSTOM-LD-SCRIPT %s
+// RUN: %clang -### %s --target=msp430 -mcpu=msp430g2553 \
+// RUN:   --sysroot=%S/Inputs/basic_msp430_tree \
+// RUN:   -T custom_script.ld 2>&1 \
+// RUN:   | FileCheck -check-prefix=CUSTOM-LD-SCRIPT %s
 // CUSTOM-LD-SCRIPT: "{{.*}}/Inputs/basic_msp430_tree/lib/gcc/msp430-elf/8.3.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}msp430-elf-ld"
 // CUSTOM-LD_SCRIPT-NOT: "-Tmsp430g2553.ld"
 // CUSTOM-LD-SCRIPT: "-T" "custom_script.ld"
 // CUSTOM-LD_SCRIPT-NOT: "-Tmsp430g2553.ld"
 
 // Test for compiling for simulator
 
 // RUN: %clang -### %s --target=msp430 -mmcu=msp430g2553 \
 // RUN:   -msim -rtlib=libgcc --sysroot=%S/Inputs/basic_msp430_tree > %t 2>&1
+// RUN: %clang -### %s --target=msp430 -mcpu=msp430g2553 \
+// RUN:   -msim -rtlib=libgcc --sysroot=%S/Inputs/basic_msp430_tree > %t 2>&1
 // RUN: FileCheck -check-prefix=SIMULATOR-POS %s < %t
 // RUN: FileCheck -check-prefix=SIMULATOR-NEG %s < %t
 // SIMULATOR-POS: "{{.*}}/Inputs/basic_msp430_tree/lib/gcc/msp430-elf/8.3.1/../../..{{/|\\\\}}..{{/|\\\\}}bin{{/|\\\\}}msp430-elf-ld"
 // SIMULATOR-POS: "{{.*}}/Inputs/basic_msp430_tree{{/|\\\\}}msp430-elf{{/|\\\\}}lib/430{{/|\\\\}}crt0.o"
 // SIMULATOR-POS: "{{.*}}/Inputs/basic_msp430_tree/lib/gcc/msp430-elf/8.3.1/430{{/|\\\\}}crtbegin_no_eh.o"
 // SIMULATOR-POS: "-L{{.*}}/Inputs/basic_msp430_tree/lib/gcc/msp430-elf/8.3.1/430"
 // SIMULATOR-POS: "-L{{.*}}/Inputs/basic_msp430_tree{{/|\\\\}}msp430-elf{{/|\\\\}}lib/430"
 // SIMULATOR-POS: "-lgcc" "--start-group" "-lmul_none" "-lc" "-lgcc" "-lcrt" "-lsim" "--undefined=__crt0_call_exit" "--end-group"