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Simplify the codegen in iter_vec_loop #22438

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Merged
merged 1 commit into from
Feb 19, 2015
Merged

Simplify the codegen in iter_vec_loop #22438

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51 changes: 14 additions & 37 deletions src/librustc_trans/trans/tvec.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -426,49 +426,26 @@ pub fn iter_vec_loop<'blk, 'tcx, F>(bcx: Block<'blk, 'tcx>,
let _icx = push_ctxt("tvec::iter_vec_loop");
let fcx = bcx.fcx;

let next_bcx = fcx.new_temp_block("expr_repeat: while next");
let loop_bcx = fcx.new_temp_block("expr_repeat");
let cond_bcx = fcx.new_temp_block("expr_repeat: loop cond");
let body_bcx = fcx.new_temp_block("expr_repeat: body: set");
let inc_bcx = fcx.new_temp_block("expr_repeat: body: inc");
Br(bcx, loop_bcx.llbb, DebugLoc::None);
let next_bcx = fcx.new_temp_block("expr_repeat: next");

let loop_counter = {
// i = 0
let i = alloca(loop_bcx, bcx.ccx().int_type(), "__i");
Store(loop_bcx, C_uint(bcx.ccx(), 0us), i);
Br(bcx, loop_bcx.llbb, DebugLoc::None);

Br(loop_bcx, cond_bcx.llbb, DebugLoc::None);
i
};
let loop_counter = Phi(loop_bcx, bcx.ccx().int_type(), &[C_uint(bcx.ccx(), 0us)], &[bcx.llbb]);

{ // i < count
let lhs = Load(cond_bcx, loop_counter);
let rhs = count;
let cond_val = ICmp(cond_bcx, llvm::IntULT, lhs, rhs, DebugLoc::None);
let bcx = loop_bcx;

CondBr(cond_bcx, cond_val, body_bcx.llbb, next_bcx.llbb, DebugLoc::None);
}

{ // loop body
let i = Load(body_bcx, loop_counter);
let lleltptr = if vt.llunit_alloc_size == 0 {
data_ptr
} else {
InBoundsGEP(body_bcx, data_ptr, &[i])
};
let body_bcx = f(body_bcx, lleltptr, vt.unit_ty);

Br(body_bcx, inc_bcx.llbb, DebugLoc::None);
}

{ // i += 1
let i = Load(inc_bcx, loop_counter);
let plusone = Add(inc_bcx, i, C_uint(bcx.ccx(), 1us), DebugLoc::None);
Store(inc_bcx, plusone, loop_counter);
let lleltptr = if vt.llunit_alloc_size == 0 {
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It seems that we could just bracket the whole loop in this and avoid emitting anything at all for zero sized types?

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The f callback might emit code that has side-effects WRT something else than the array itself, we can't just omit that.

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Ah, of course.

data_ptr
} else {
InBoundsGEP(bcx, data_ptr, &[loop_counter])
};
let bcx = f(bcx, lleltptr, vt.unit_ty);
let plusone = Add(bcx, loop_counter, C_uint(bcx.ccx(), 1us), DebugLoc::None);
AddIncomingToPhi(loop_counter, plusone, bcx.llbb);

Br(inc_bcx, cond_bcx.llbb, DebugLoc::None);
}
let cond_val = ICmp(bcx, llvm::IntULT, plusone, count, DebugLoc::None);
CondBr(bcx, cond_val, loop_bcx.llbb, next_bcx.llbb, DebugLoc::None);

next_bcx
}
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