Bug 22163 – [REG 2.094.0] wrong code with static float array and delegate accessing it

Reduced code: ``` import core.stdc.stdio; void drawText(float[2] size) { printf("%f %f\n", size[0], size[1]); scope dg = (int x) => size[0]; } extern(C) void main() { float[2] size = [10.0, 20.0]; printf("%f %f\n", size[0], size[1]); drawText(size); } ``` Prints: 10.000000 20.000000 10.000000 0.000000 It should print 20 instead of 0 for `size[1]` the second time. It works with LDC, so I assume it's a backend / glue code bug. It also works on Windows, or when replacing `float` with `int`, or without the delegate.

So far I found out that the delegate makes the parameter volatile in dmd/tocsym.d: ``` if (vd.nestedrefs.dim) { /* Symbol is accessed by a nested function. Make sure * it is not put in a register, and that the optimizer * assumes it is modified across function calls and pointer * dereferences. */ //printf("\tnested ref, not register\n"); type_setcv(&t, t.Tty | mTYvolatile); } ``` Then in dmd/backend/cod1.d:FuncParamRegs_alloc the float[2] is combined into the xmm0 register: ``` if (tyaggregate(ty)) { /* ... */ else if (tybasic(t.Tty) == TYarray) { if (I64) argtypes(t, targ1, targ2); } ``` But in dmd/backend/cod3.d:prolog_loadparams this branch isn't taken: ``` // This logic is same as FuncParamRegs_alloc function at src/dmd/backend/cod1.d // // Find suitable SROA based on the element type // (Don't put volatile parameters in registers) if (tyb == TYarray && !(t.Tty & mTYvolatile)) { type *targ1; argtypes(t, targ1, t2); if (targ1) t = targ1; } ``` Which makes it load a `double` from xmm0 instead of a `float`. The comment "This logic is same as FuncParamRegs_alloc function" is no longer true, but I'm not certain what the fix is. I doubt `volatile` should affect the abi, but "Don't put volatile parameters in registers" was written for a reason so I don't want to remove that without consideration.

@dkorpel created dlang/dmd pull request #13256 "Fix issue 22163 - wrong code with static float array and delegate accessing it" fixing this issue: - Fix issue 22163 - wrong code with static float array and delegate accessing it https://github.com/dlang/dmd/pull/13256

*** Issue 22588 has been marked as a duplicate of this issue. ***

dlang/dmd pull request #13256 "Fix issue 22163 - wrong code with static float array and delegate accessing it" was merged into stable: - 78d2e0833d21680de1090ad3d3fd68dd3205739e by dkorpel: Fix issue 22163 - wrong code with static float array and delegate accessing it https://github.com/dlang/dmd/pull/13256