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machinst x64: use the (base,offset) addressing mode even in the presence of a uextend;

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This commit is contained in:
Benjamin Bouvier
2020-10-07 15:47:02 +02:00
parent 88d975d396
commit 3980a43cda
2 changed files with 69 additions and 1 deletions
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29
cranelift/codegen/src/isa/x64/lower.rs
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@@ -449,6 +449,7 @@ fn lower_to_amode<C: LowerCtx<I = Inst>>(ctx: &mut C, spec: InsnInput, offset: i
// We now either have an add that we must materialize, or some other input; as well as the
// final offset.
if let Some(add) = matches_input(ctx, spec, Opcode::Iadd) {
debug_assert_eq!(ctx.output_ty(add, 0), types::I64);
let add_inputs = &[
InsnInput {
insn: add,
@@ -480,7 +481,33 @@ fn lower_to_amode<C: LowerCtx<I = Inst>>(ctx: &mut C, spec: InsnInput, offset: i
)
} else {
for i in 0..=1 {
if let Some(cst) = ctx.get_input(add, i).constant {
let input = ctx.get_input(add, i);
// Try to pierce through uextend.
if let Some(uextend) = matches_input(
ctx,
InsnInput {
insn: add,
input: i,
},
Opcode::Uextend,
) {
if let Some(cst) = ctx.get_input(uextend, 0).constant {
// Zero the upper bits.
let input_size = ctx.input_ty(uextend, 0).bits() as u64;
let shift: u64 = 64 - input_size;
let uext_cst: u64 = (cst << shift) >> shift;
let final_offset = (offset as i64).wrapping_add(uext_cst as i64);
if low32_will_sign_extend_to_64(final_offset as u64) {
let base = put_input_in_reg(ctx, add_inputs[1 - i]);
return Amode::imm_reg(final_offset as u32, base);
}
}
}
// If it's a constant, add it directly!
if let Some(cst) = input.constant {
let final_offset = (offset as i64).wrapping_add(cst as i64);
if low32_will_sign_extend_to_64(final_offset as u64) {
let base = put_input_in_reg(ctx, add_inputs[1 - i]);