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riscv: fix how we calculate stack offsets. allows for pass by reference arguments.

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This commit is contained in:
David Rubin 2024-03-25 03:28:11 -07:00
parent c96989aa4b
commit 06089fc89a
1 changed files with 11 additions and 4 deletions
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15
src/arch/riscv64/Emit.zig
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@ -536,11 +536,18 @@ fn lowerMir(emit: *Emit) !void {
const data = mir_datas[inst].i_type;
// TODO: probably create a psuedo instruction for s0 loads/stores instead of this.
if (data.rs1 == .s0) {
const casted_size = math.cast(i12, emit.stack_size) orelse {
return emit.fail("TODO: support bigger stack sizes lowerMir", .{});
};
const offset = mir_datas[inst].i_type.imm12;
mir_datas[inst].i_type.imm12 = -(casted_size - 12 - offset);
// sp + 32 (aka s0)
// ra -- previous ra spilled
// s0 -- previous s0 spilled
// --- this is -16(s0)
// TODO: this "+ 8" is completely arbiratary as the largest possible store
// we don't want to actually use it. instead we need to calculate the difference
// between the first and second stack store and use it instead.
mir_datas[inst].i_type.imm12 = -(16 + offset + 8);
}
}