Instruction selection failure: f64->f32 truncation into a store

[xdoardo]

Compiling the following Rust code

let x1p_126 = f64::from_bits(0x3810000000000000); // 0x1p-126 == 2^-126
unsafe { ::core::ptr::read_volatile(&((x1p_126 / x) as f32)) };

produces this instruction selection failure:

rustc-LLVM ERROR: Cannot select: 0x1498f16e0: ch = store<(store (s32) into %ir.2, addrspace 200), trunc to f32> 0x1498f3c00, 0x149906980, FrameIndex:c64<0>, undef:c64, library/compiler-builtins/compiler-builtins/src/math/../../../libm/src/math/tgamma.rs:172:25
  0x149906980: f64,ch,glue = CopyFromReg 0x1499069f0, Register:f64 $c10, 0x1499069f0:1, library/compiler-builtins/compiler-builtins/src/math/../../../libm/src/math/tgamma.rs:172:25
    0x1499069f0: ch,glue = callseq_end 0x149905470, TargetConstant:i32<0>, TargetConstant:i32<0>, 0x149905470:1, library/compiler-builtins/compiler-builtins/src/math/../../../libm/src/math/tgamma.rs:172:25
      0x149905470: ch,glue = RISCVISD::CAP_LIB_CALL 0x149906670, TargetExternalSymbol:c64'__divdf3' [TF=21], Register:f64 $c10, Register:f64 $c11, RegisterMask:Untyped, 0x149906670:1, library/compiler-builtins/compiler-builtins/src/math/../../../libm/src/math/tgamma.rs:172:25
        0x149906670: ch,glue = CopyToReg 0x1499066e0, Register:f64 $c11, 0x1498f40d0, 0x1499066e0:1, library/compiler-builtins/compiler-builtins/src/math/../../../libm/src/math/tgamma.rs:172:25
          0x1498f40d0: f64,ch = CopyFromReg 0x138e59238, Register:f64 %44, library/compiler-builtins/compiler-builtins/src/math/../../../libm/src/math/tgamma.rs:172:25
          0x1499066e0: ch,glue = CopyToReg 0x149905160, Register:f64 $c10, 0x149906fa0, library/compiler-builtins/compiler-builtins/src/math/../../../libm/src/math/tgamma.rs:172:25
            0x149906fa0: f64 = bitcast 0x149907010
              0x149907010: c64 = llvm.cheri.cap.high.set TargetConstant:i32<38>, 0x149906e50, Constant:i32<940572672>
                0x149906e50: c64 = INSERT_SUBREG undef:f64, Constant:i32<0>, TargetConstant:i32<4>

Culprit .ll module disguised as a .txt to make GH happy:
compiler_builtins-410dc471d12f38f0.compiler_builtins.c30927b5eaf23c96-cgu.022.rcgu.txt

[resistor]

Fixed by #254