riscv64 behavior tests stopped passing with LLVM 14 upgrade

[andrewrk]

They pass for me locally but stopped working on the CI:

770/1319 test.remainder division... FAIL (TestUnexpectedResult)
771/1319 test.float remainder division using @rem... FAIL (TestUnexpectedResult)
772/1319 test.float modulo division using @mod... FAIL (TestUnexpectedResult)
780/1319 test.@ceil f80... FAIL (TestUnexpectedResult)
781/1319 test.@ceil f128... FAIL (TestUnexpectedResult)
789/1319 test.NaN comparison... FAIL (TestUnexpectedResult)
1223 passed; 90 skipped; 6 failed.
error: the following test command failed with exit code 1:
qemu-riscv64 /workspace/zig-cache/o/ba238760a1396f763444a4cf0e622395/test /workspace/stage2/bin/zig
test...The following command exited with error code 1:
/workspace/stage2/bin/zig test /workspace/test/behavior.zig --test-name-prefix behavior-riscv64-linux-none-Debug-bare-multi-default  --cache-dir /workspace/zig-cache --global-cache-dir /root/.cache/zig --name test -fno-single-threaded -target riscv64-linux-none -mcpu baseline_rv64 --test-cmd qemu-riscv64 --test-cmd-bin -I /workspace/test --zig-lib-dir /workspace/lib --enable-cache 

This issue is to figure out why, fix it, and to re-enable test coverage.

[andrewrk]

This affects stage2, not stage1.

[topolarity]

At least locally, I'm seeing problems on stage 1 as well

My stage 1 problem was resolved by applying https://reviews.llvm.org/D129431 (and also nuking the cache to clear out the old, bad compiler_rt)

I'm now able to reproduce the stage 2-specific issue mentioned here

[topolarity]

Appears to be compiler-rt/C ABI related.

The __cmptf2 generated by stage2 is missing the signext attribute that stage1 gives it (ABI logic added in #8152).

Stepping through with a debugger confirms that the missing sext instruction is one place where the tests diverge on stage 2

[topolarity]

Also, notice that the compiler_rt tests for stage2 are failing in general:

$ ./stage2/bin/zig test lib/compiler_rt.zig -target riscv64-linux-none -mcpu baseline_rv64 --test-cmd qemu-riscv64 --test-cmd-bin --strip
Test [22/235] test.ceil128... FAIL (TestUnexpectedResult)
Test [37/235] test.floor128... FAIL (TestUnexpectedResult)
Test [44/235] test.128... FAIL (TestUnexpectedResult)
Test [64/235] test.round128... FAIL (TestUnexpectedResult)
...
Test [139/235] test.fmodq... FAIL (TestUnexpectedResult)
225 passed; 5 skipped; 5 failed.
error: the following test command failed with exit code 1:
qemu-riscv64 lib/zig-cache/o/bc1b86c1268e5765aaf2c1d2b33b3174/test /home/topolarity/repos/zig/stage2/bin/zig

[andrewrk]

Appears to be compiler-rt/C ABI related.

The __cmptf2 generated by stage2 is missing the signext attribute that stage1 gives it (ABI logic added in #8152).

Stepping through with a debugger confirms that the missing sext instruction is one place where the tests diverge on stage 2

This comment was spot on! Fix coming right up...