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Use EBB offsets for encoding RISC-V branches.

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Stop emitting EBB relocations. Use the offsets computed by
relax_branches() to encode the correct displacements immediately.
This commit is contained in:
Jakob Stoklund Olesen
2017-04-06 11:18:38 -07:00
parent 8a3f538441
commit 856a67ca3a
2 changed files with 49 additions and 20 deletions
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24
lib/cretonne/src/isa/riscv/binemit.rs
View File

@@ -3,10 +3,12 @@
use binemit::{CodeSink, Reloc, bad_encoding};
use ir::{Function, Inst, InstructionData};
use isa::RegUnit;
use predicates::is_signed_int;
include!(concat!(env!("OUT_DIR"), "/binemit-riscv.rs"));
/// RISC-V relocation kinds.
#[allow(dead_code)]
pub enum RelocKind {
/// A conditional (SB-type) branch to an EBB.
Branch,
@@ -213,17 +215,17 @@ fn recipe_u<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut CS) {
/// imm rs2 rs1 funct3 imm opcode
/// 25 20 15 12 7 0
///
/// The imm bits are not encoded by this function. They encode the relative distance to the
/// destination block, handled by a relocation.
///
/// Encoding bits: `opcode[6:2] | (funct3 << 5)`
fn put_sb<CS: CodeSink + ?Sized>(bits: u16, rs1: RegUnit, rs2: RegUnit, sink: &mut CS) {
fn put_sb<CS: CodeSink + ?Sized>(bits: u16, imm: i64, rs1: RegUnit, rs2: RegUnit, sink: &mut CS) {
let bits = bits as u32;
let opcode5 = bits & 0x1f;
let funct3 = (bits >> 5) & 0x7;
let rs1 = rs1 as u32 & 0x1f;
let rs2 = rs2 as u32 & 0x1f;
assert!(is_signed_int(imm, 13, 1), "SB out of range {:#x}", imm);
let imm = imm as u32;
// 0-6: opcode
let mut i = 0x3;
i |= opcode5 << 2;
@@ -231,6 +233,12 @@ fn put_sb<CS: CodeSink + ?Sized>(bits: u16, rs1: RegUnit, rs2: RegUnit, sink: &m
i |= rs1 << 15;
i |= rs2 << 20;
// The displacement is completely hashed up.
i |= ((imm >> 11) & 0x1) << 7;
i |= ((imm >> 1) & 0xf) << 8;
i |= ((imm >> 5) & 0x3f) << 25;
i |= ((imm >> 12) & 0x1) << 31;
sink.put4(i);
}
@@ -240,9 +248,11 @@ fn recipe_sb<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut CS)
ref args,
..
} = func.dfg[inst] {
let dest = func.offsets[destination] as i64;
let disp = dest - sink.offset() as i64;
let args = &args.as_slice(&func.dfg.value_lists)[0..2];
sink.reloc_ebb(RelocKind::Branch.into(), destination);
put_sb(func.encodings[inst].bits(),
disp,
func.locations[args[0]].unwrap_reg(),
func.locations[args[1]].unwrap_reg(),
sink);
@@ -257,9 +267,11 @@ fn recipe_sbzero<CS: CodeSink + ?Sized>(func: &Function, inst: Inst, sink: &mut
ref args,
..
} = func.dfg[inst] {
let dest = func.offsets[destination] as i64;
let disp = dest - sink.offset() as i64;
let args = &args.as_slice(&func.dfg.value_lists)[0..1];
sink.reloc_ebb(RelocKind::Branch.into(), destination);
put_sb(func.encodings[inst].bits(),
disp,
func.locations[args[0]].unwrap_reg(),
0,
sink);