Crash with MIPS16 multiply

[jdeguire]

Bugzilla Link	49146
Version	11.0
OS	Linux
Attachments	Clang output and crash report files
CC	@atanasyan

Extended Description

Clang 11.0.1 crashes with a stack trace and message telling me to file a bug here when I build a module containing the following code in MIPS16 mode:

---

static unsigned baz(unsigned n, unsigned m)
{
/* NOTE: Using any of these other operators works fine,
only the multiply causes the crash.
*/
// return n + m;
// return n - m;
return n * m;
// return n / m;
}

int bar(void)
{
return 42;
}

void foo(void)
{
int bleh = bar();
baz(bleh, 55);
}

This is on a version of Clang I built in Debug mode for x86, MIPS, and ARM targets on Ubuntu 20.04 on Windows 10 WSL.

Here is the start of the output from Clang, the rest is included in the attached ZIP file:

---

fatal error: error in backend: Not supported instr: <MCInst 464 >
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace, preprocessed source, and associated run script.
Stack dump:
0. Program arguments: ./pic32clang/install/bin/clang -c mips16_simple.c -o mips16_simple.o -target mipsel-linux-gnu-musl -march=mips32r2 -g -O0 -msoft-float -mfloat-abi=soft -mips16

1. parser at end of file
2. Code generation
3. Running pass 'Function Pass Manager' on module 'mips16_simple.c'.
4. Running pass 'Mips Assembly Printer' on function '@baz'

---

Also included in the ZIP file are the two files that the crash report told me to include. The document "How To Submit an LLVM Bug Report" says to run "llc" to see if that crashes, but it does not (this is different from my previously-submitted bug #​49042, which does crash llc).

[atanasyan]

Thanks for the report. MIPS16 support is in an experimental state now. Direct machine code emission has a lot of bugs.

[xgupta]

Seems fixed now on trunk - https://godbolt.org/z/859ra799M.

[jdeguire]

Excellent! Indeed it does seem fixed and looks to be generating valid instructions.

Thanks for checking! It looks like I can close this.