llvm dev - Mar 2020 - llvm-objdump cannot recognize mul&mulh RISC-V M Instructions

I am using llvm-project compiling risc-v programs.

llvm-project version:dd8a2013dc1804be1b7d9cffacad2e984300bd22

Instructons to build LLVM+clang:

```
cmake -G Ninja
-DCMAKE_INSTALL_PREFIX=/home/llvm/workspace/llvm/llvm-project/llvm_install
-DCMAKE_BUILD_TYPE="Release"
-DDEFAULT_SYSROOT="/home/llvm/workspace/riscv/riscv-tc-20200220/bin/riscv32-unknown-elf"
-DGCC_INSTALL_PREFIX="/home/llvm/workspace/riscv/riscv-tc-20200220"
-DLLVM_DEFAULT_TARGET_TRIPLE="riscv32-unknown-elf"
-DLLVM_ENABLE_PROJECTS="clang;lld;libc"
-DLLVM_TARGETS_TO_BUILD="RISCV"
../llvm
```

Instructions to compile and dump:

```
RISCV_GCC_OPTS ?= -mcmodel=medany -static -O3 -std=gnu99 -fno-common
-fno-builtin -march=rv32im -mabi=ilp32 -DMB_ADDR=0x80FFFFC
--target=riscv64-unknown-elf
--sysroot=/home/llvm/workspace/riscv/riscv-tc-20200220/bin/riscv64-unknown-elf
--gcc-toolchain=/home/llvm/workspace/riscv/riscv-tc-20200220
RISCV_LINK_OPTS ?= -static -nostdlib -nostartfiles -lm -lgcc -T
/home/llvm/workspace/HRV_IDE/common/test.ld
newlib_dir
:/home/llvm/workspace/llvm/llvm-project/llvm_install/riscv64-unknown-elf/include
src_dir := $(WORK_DIR)/src/$(PROJ)
incs  += -I$(WORK_DIR)/env -I$(WORK_DIR)/common -I$(src_dir) -I$(newlib_dir)
src := $(wildcard $(src_dir)/*.c) $(wildcard $(WORK_DIR)/common/*.c)
$(wildcard $(WORK_DIR)/common/*.S)

$(RISCV_clang) $(incs) $(RISCV_GCC_OPTS) -o $(WORK_DIR)/build/$@/$@ $(src)
$(RISCV_LINK_OPTS) --verbose
$(RISCV_OBJDUMP) -d $(WORK_DIR)/build/$@/$@ > $(WORK_DIR)/build/$@/$@.S
$(RISCV_LLVM_OBJDUMP) --arch=rv32imac -D $(WORK_DIR)/build/$@/$@ >
$(WORK_DIR)/build/$@/$@.ASM
```
gcc objdump result:
```
4001168: 00052383           lw t2,0(a0)
 400116c: 979a                 add a5,a5,t1
 400116e: 439c                 lw a5,0(a5)
 4001170: 0308a533           mulhsu a0,a7,a6
```

llvm-objdump result:

```
 4001168: 83 23 05 00                   lw t2, 0(a0)
 400116c: 9a 97                         add a5, a5, t1
 400116e: 9c 43                         lw a5, 0(a5)
 4001170: 33 a5 08 03                   <unknown>
```

Does anyone knows what is the problem and how to fix it?
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Hi,

Unlike GNU objdump, llvm-objdump doesn't assume that for RISC-V all
standard extensions are available by default, and so need to be
provided on the command line. I'm not aware of a flag that you can
pass a RISC-V ISA string to (from your command it seems --arch doesn't
do this for you), but you can enable the disassembly of instructions
using the underlying attributes and the --mattr flag, so in your case
adding `--mattr=+m` to your llvm-objdump command (I think `--mattr=m`
should work as well).

Hope this helps.

Thanks,
Simon

On Fri, Mar 27, 2020 at 9:23 AM Junning Wu via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
> I am using llvm-project compiling risc-v programs.
>
> llvm-project version:dd8a2013dc1804be1b7d9cffacad2e984300bd22
>
> Instructons to build LLVM+clang:
>
> ```
> cmake -G Ninja
-DCMAKE_INSTALL_PREFIX=/home/llvm/workspace/llvm/llvm-project/llvm_install
-DCMAKE_BUILD_TYPE="Release"
-DDEFAULT_SYSROOT="/home/llvm/workspace/riscv/riscv-tc-20200220/bin/riscv32-unknown-elf"
-DGCC_INSTALL_PREFIX="/home/llvm/workspace/riscv/riscv-tc-20200220"
-DLLVM_DEFAULT_TARGET_TRIPLE="riscv32-unknown-elf"
-DLLVM_ENABLE_PROJECTS="clang;lld;libc"
-DLLVM_TARGETS_TO_BUILD="RISCV" ../llvm
> ```
>
> Instructions to compile and dump:
>
> ```
> RISCV_GCC_OPTS ?= -mcmodel=medany -static -O3 -std=gnu99 -fno-common
-fno-builtin -march=rv32im -mabi=ilp32 -DMB_ADDR=0x80FFFFC
--target=riscv64-unknown-elf
--sysroot=/home/llvm/workspace/riscv/riscv-tc-20200220/bin/riscv64-unknown-elf
--gcc-toolchain=/home/llvm/workspace/riscv/riscv-tc-20200220
> RISCV_LINK_OPTS ?= -static -nostdlib -nostartfiles -lm -lgcc -T
/home/llvm/workspace/HRV_IDE/common/test.ld
> newlib_dir :=
/home/llvm/workspace/llvm/llvm-project/llvm_install/riscv64-unknown-elf/include
> src_dir := $(WORK_DIR)/src/$(PROJ)
> incs  += -I$(WORK_DIR)/env -I$(WORK_DIR)/common -I$(src_dir)
-I$(newlib_dir)
> src := $(wildcard $(src_dir)/*.c) $(wildcard $(WORK_DIR)/common/*.c)
$(wildcard $(WORK_DIR)/common/*.S)
>
> $(RISCV_clang) $(incs) $(RISCV_GCC_OPTS) -o $(WORK_DIR)/build/$@/$@ $(src)
$(RISCV_LINK_OPTS) --verbose
> $(RISCV_OBJDUMP) -d $(WORK_DIR)/build/$@/$@ > $(WORK_DIR)/build/$@/$@.S
> $(RISCV_LLVM_OBJDUMP) --arch=rv32imac -D $(WORK_DIR)/build/$@/$@ >
$(WORK_DIR)/build/$@/$@.ASM
> ```
> gcc objdump result:
> ```
> 4001168: 00052383           lw t2,0(a0)
>  400116c: 979a                 add a5,a5,t1
>  400116e: 439c                 lw a5,0(a5)
>  4001170: 0308a533           mulhsu a0,a7,a6
> ```
>
> llvm-objdump result:
>
> ```
>  4001168: 83 23 05 00                   lw t2, 0(a0)
>  400116c: 9a 97                         add a5, a5, t1
>  400116e: 9c 43                         lw a5, 0(a5)
>  4001170: 33 a5 08 03                   <unknown>
> ```
>
> Does anyone knows what is the problem and how to fix it?
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

Awesome, thanks!

‘ --mattr=m  ’ works well, I can see mul & mulh instructions.


On Fri, Mar 27, 2020 at 7:07 PM Simon Cook <simon.cook at embecosm.com>
wrote:
> Hi,
>
> Unlike GNU objdump, llvm-objdump doesn't assume that for RISC-V all
> standard extensions are available by default, and so need to be
> provided on the command line. I'm not aware of a flag that you can
> pass a RISC-V ISA string to (from your command it seems --arch doesn't
> do this for you), but you can enable the disassembly of instructions
> using the underlying attributes and the --mattr flag, so in your case
> adding `--mattr=+m` to your llvm-objdump command (I think `--mattr=m`
> should work as well).
>
> Hope this helps.
>
> Thanks,
> Simon
>
> On Fri, Mar 27, 2020 at 9:23 AM Junning Wu via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> >
> > I am using llvm-project compiling risc-v programs.
> >
> > llvm-project version:dd8a2013dc1804be1b7d9cffacad2e984300bd22
> >
> > Instructons to build LLVM+clang:
> >
> > ```
> > cmake -G Ninja
> -DCMAKE_INSTALL_PREFIX=/home/llvm/workspace/llvm/llvm-project/llvm_install
> -DCMAKE_BUILD_TYPE="Release"
>
-DDEFAULT_SYSROOT="/home/llvm/workspace/riscv/riscv-tc-20200220/bin/riscv32-unknown-elf"
>
-DGCC_INSTALL_PREFIX="/home/llvm/workspace/riscv/riscv-tc-20200220"
> -DLLVM_DEFAULT_TARGET_TRIPLE="riscv32-unknown-elf"
> -DLLVM_ENABLE_PROJECTS="clang;lld;libc"
-DLLVM_TARGETS_TO_BUILD="RISCV"
> ../llvm
> > ```
> >
> > Instructions to compile and dump:
> >
> > ```
> > RISCV_GCC_OPTS ?= -mcmodel=medany -static -O3 -std=gnu99 -fno-common
> -fno-builtin -march=rv32im -mabi=ilp32 -DMB_ADDR=0x80FFFFC
> --target=riscv64-unknown-elf
>
--sysroot=/home/llvm/workspace/riscv/riscv-tc-20200220/bin/riscv64-unknown-elf
> --gcc-toolchain=/home/llvm/workspace/riscv/riscv-tc-20200220
> > RISCV_LINK_OPTS ?= -static -nostdlib -nostartfiles -lm -lgcc -T
> /home/llvm/workspace/HRV_IDE/common/test.ld
> > newlib_dir :>
/home/llvm/workspace/llvm/llvm-project/llvm_install/riscv64-unknown-elf/include
> > src_dir := $(WORK_DIR)/src/$(PROJ)
> > incs  += -I$(WORK_DIR)/env -I$(WORK_DIR)/common -I$(src_dir)
> -I$(newlib_dir)
> > src := $(wildcard $(src_dir)/*.c) $(wildcard $(WORK_DIR)/common/*.c)
> $(wildcard $(WORK_DIR)/common/*.S)
> >
> > $(RISCV_clang) $(incs) $(RISCV_GCC_OPTS) -o $(WORK_DIR)/build/$@/$@
> $(src) $(RISCV_LINK_OPTS) --verbose
> > $(RISCV_OBJDUMP) -d $(WORK_DIR)/build/$@/$@ >
$(WORK_DIR)/build/$@/$@.S
> > $(RISCV_LLVM_OBJDUMP) --arch=rv32imac -D $(WORK_DIR)/build/$@/$@ >
> $(WORK_DIR)/build/$@/$@.ASM
> > ```
> > gcc objdump result:
> > ```
> > 4001168: 00052383           lw t2,0(a0)
> >  400116c: 979a                 add a5,a5,t1
> >  400116e: 439c                 lw a5,0(a5)
> >  4001170: 0308a533           mulhsu a0,a7,a6
> > ```
> >
> > llvm-objdump result:
> >
> > ```
> >  4001168: 83 23 05 00                   lw t2, 0(a0)
> >  400116c: 9a 97                         add a5, a5, t1
> >  400116e: 9c 43                         lw a5, 0(a5)
> >  4001170: 33 a5 08 03                   <unknown>
> > ```
> >
> > Does anyone knows what is the problem and how to fix it?
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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On Fri, Mar 27, 2020 at 7:07 AM Simon Cook via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hi,
>
> Unlike GNU objdump, llvm-objdump doesn't assume that for RISC-V all
> standard extensions are available by default, and so need to be
> provided on the command line. I'm not aware of a flag that you can
> pass a RISC-V ISA string to (from your command it seems --arch doesn't
> do this for you), but you can enable the disassembly of instructions
> using the underlying attributes and the --mattr flag, so in your case
> adding `--mattr=+m` to your llvm-objdump command (I think `--mattr=m`
> should work as well).
>
Seems like it'd make sense to change this? Is there any benefit to not
disassemble the standard extensions unless requested?
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