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Optimizations to egraph framework (#5391)

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* Optimizations to egraph framework:

- Save elaborated results by canonical value, not latest value (union
  value). Previously we were artificially skipping and re-elaborating
  some values we already had because we were not finding them in the
  map.

- Make some changes to handling of icmp results: when icmp became
  I8-typed (when bools went away), many uses became `(uextend $I32 (icmp
  $I8 ...))`, and so patterns in lowering backends were no longer
  matching.

  This PR includes an x64-specific change to match `(brz (uextend (icmp
  ...)))` and similarly for `brnz`, but it also takes advantage of the
  ability to write rules easily in the egraph mid-end to rewrite selects
  with icmp inputs appropriately.

- Extend constprop to understand selects in the egraph mid-end.

With these changes, bz2.wasm sees a ~1% speedup, and spidermonkey.wasm
with a fib.js input sees a 16.8% speedup:

```
$ time taskset 1 target/release/wasmtime run --allow-precompiled --dir=. ./spidermonkey.base.cwasm ./fib.js
1346269
taskset 1 target/release/wasmtime run --allow-precompiled --dir=.  ./fib.js  2.14s user 0.01s system 99% cpu 2.148 total
$ time taskset 1 target/release/wasmtime run --allow-precompiled --dir=. ./spidermonkey.egraphs.cwasm ./fib.js
1346269
taskset 1 target/release/wasmtime run --allow-precompiled --dir=.  ./fib.js  1.78s user 0.01s system 99% cpu 1.788 total
```

* Review feedback.
This commit is contained in:
Chris Fallin
2022-12-07 13:23:13 -08:00
committed by GitHub
parent c5379051c4
commit 8c55b81300
8 changed files with 90 additions and 41 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
cranelift/codegen/src/egraph/elaborate.rs
View File

@@ -277,7 +277,7 @@ impl<'a> Elaborator<'a> {
let value = self.func.dfg.resolve_aliases(value);
self.stats.elaborate_visit_node += 1;
let canonical_value = self.eclasses.find(value);
let canonical_value = self.eclasses.find_and_update(value);
debug_assert_ne!(canonical_value, Value::reserved_value());
trace!(
"elaborate: value {} canonical {} before {}",
@@ -518,8 +518,9 @@ impl<'a> Elaborator<'a> {
value: new_result,
in_block: insert_block,
};
let canonical_result = self.eclasses.find_and_update(result);
self.value_to_elaborated_value.insert_if_absent_with_depth(
result,
canonical_result,
elab_value,
scope_depth,
);
@@ -545,8 +546,9 @@ impl<'a> Elaborator<'a> {
value: result,
in_block: insert_block,
};
let canonical_result = self.eclasses.find_and_update(result);
self.value_to_elaborated_value.insert_if_absent_with_depth(
result,
canonical_result,
elab_value,
scope_depth,
);
@@ -623,8 +625,9 @@ impl<'a> Elaborator<'a> {
// map now.
for &result in self.func.dfg.inst_results(inst) {
trace!(" -> result {}", result);
let canonical_result = self.eclasses.find_and_update(result);
self.value_to_elaborated_value.insert_if_absent(
result,
canonical_result,
ElaboratedValue {
in_block: block,
value: result,

16
cranelift/codegen/src/isa/x64/lower.isle
View File

@@ -2916,10 +2916,19 @@
(let ((cmp IcmpCondResult (invert_icmp_cond_result (emit_cmp cc a b))))
(side_effect (jmp_cond_icmp cmp taken not_taken))))
(rule 2 (lower_branch (brz (uextend (icmp cc a b)) _ _) (two_targets taken not_taken))
(let ((cmp IcmpCondResult (invert_icmp_cond_result (emit_cmp cc a b))))
(side_effect (jmp_cond_icmp cmp taken not_taken))))
(rule 2 (lower_branch (brz (fcmp cc a b) _ _) (two_targets taken not_taken))
(let ((cmp FcmpCondResult (emit_fcmp (floatcc_inverse cc) a b)))
(side_effect (jmp_cond_fcmp cmp taken not_taken))))
(rule 2 (lower_branch (brz (uextend (fcmp cc a b)) _ _) (two_targets taken not_taken))
(let ((cmp FcmpCondResult (emit_fcmp (floatcc_inverse cc) a b)))
(side_effect (jmp_cond_fcmp cmp taken not_taken))))
(rule 1 (lower_branch (brz val @ (value_type $I128) _ _) (two_targets taken not_taken))
(side_effect (jmp_cond_icmp (cmp_zero_i128 (CC.NZ) val) taken not_taken)))
@@ -2936,6 +2945,13 @@
(let ((cmp FcmpCondResult (emit_fcmp cc a b)))
(side_effect (jmp_cond_fcmp cmp taken not_taken))))
(rule 2 (lower_branch (brnz (uextend (icmp cc a b)) _ _) (two_targets taken not_taken))
(side_effect (jmp_cond_icmp (emit_cmp cc a b) taken not_taken)))
(rule 2 (lower_branch (brnz (uextend (fcmp cc a b)) _ _) (two_targets taken not_taken))
(let ((cmp FcmpCondResult (emit_fcmp cc a b)))
(side_effect (jmp_cond_fcmp cmp taken not_taken))))
(rule 1 (lower_branch (brnz val @ (value_type $I128) _ _) (two_targets taken not_taken))
(side_effect (jmp_cond_icmp (cmp_zero_i128 (CC.Z) val) taken not_taken)))

20
cranelift/codegen/src/isle_prelude.rs
View File

@@ -586,6 +586,26 @@ macro_rules! isle_common_prelude_methods {
}
}
#[inline]
fn intcc_reverse(&mut self, cc: &IntCC) -> IntCC {
cc.reverse()
}
#[inline]
fn intcc_inverse(&mut self, cc: &IntCC) -> IntCC {
cc.inverse()
}
#[inline]
fn floatcc_reverse(&mut self, cc: &FloatCC) -> FloatCC {
cc.reverse()
}
#[inline]
fn floatcc_inverse(&mut self, cc: &FloatCC) -> FloatCC {
cc.inverse()
}
#[inline]
fn unpack_value_array_2(&mut self, arr: &ValueArray2) -> (Value, Value) {
let [a, b] = *arr;

20
cranelift/codegen/src/machinst/isle.rs
View File

@@ -537,26 +537,6 @@ macro_rules! isle_lower_prelude_methods {
MInst::gen_move(dst, src, ty)
}
#[inline]
fn intcc_reverse(&mut self, cc: &IntCC) -> IntCC {
cc.reverse()
}
#[inline]
fn intcc_inverse(&mut self, cc: &IntCC) -> IntCC {
cc.inverse()
}
#[inline]
fn floatcc_reverse(&mut self, cc: &FloatCC) -> FloatCC {
cc.reverse()
}
#[inline]
fn floatcc_inverse(&mut self, cc: &FloatCC) -> FloatCC {
cc.inverse()
}
/// Generate the return instruction.
fn gen_return(&mut self, (list, off): ValueSlice) {
let rets = (off..list.len(&self.lower_ctx.dfg().value_lists))

22
cranelift/codegen/src/opts/algebraic.isle
View File

@@ -185,3 +185,25 @@
(remat x))
(rule (simplify x @ (f64const _ _))
(remat x))
;; Optimize icmp-of-icmp.
(rule (simplify (icmp ty
(IntCC.NotEqual)
(uextend _ inner @ (icmp ty _ _ _))
(iconst _ (u64_from_imm64 0))))
(subsume inner))
(rule (simplify (icmp ty
(IntCC.Equal)
(uextend _ (icmp ty cc x y))
(iconst _ (u64_from_imm64 0))))
(subsume (icmp ty (intcc_inverse cc) x y)))
;; Optimize select-of-uextend-of-icmp to select-of-icmp, because
;; select can take an I8 condition too.
(rule (simplify
(select ty (uextend _ c @ (icmp _ _ _ _)) x y))
(select ty c x y))
(rule (simplify
(select ty (uextend _ c @ (icmp _ _ _ _)) x y))
(select ty c x y))

7
cranelift/codegen/src/opts/cprop.isle
View File

@@ -130,5 +130,12 @@
(bxor ty (bxor ty x k1 @ (iconst ty _)) k2 @ (iconst ty _)))
(bxor ty x (bxor ty k1 k2)))
(rule (simplify
(select ty (iconst _ (u64_from_imm64 (u64_nonzero _))) x y))
x)
(rule (simplify
(select ty (iconst _ (u64_from_imm64 0)) x y))
y)
;; TODO: fadd, fsub, fmul, fdiv, fneg, fabs

18
cranelift/codegen/src/prelude.isle
View File

@@ -206,6 +206,24 @@
(decl mem_flags_trusted () MemFlags)
(extern constructor mem_flags_trusted mem_flags_trusted)
;;;; Helpers for Working with Flags ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Reverse an IntCC flag.
(decl intcc_reverse (IntCC) IntCC)
(extern constructor intcc_reverse intcc_reverse)
;; Invert an IntCC flag.
(decl intcc_inverse (IntCC) IntCC)
(extern constructor intcc_inverse intcc_inverse)
;; Reverse an FloatCC flag.
(decl floatcc_reverse (FloatCC) FloatCC)
(extern constructor floatcc_reverse floatcc_reverse)
;; Invert an FloatCC flag.
(decl floatcc_inverse (FloatCC) FloatCC)
(extern constructor floatcc_inverse floatcc_inverse)
;;;; Helper Clif Extractors ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; An extractor that only matches types that can fit in 16 bits.

17
cranelift/codegen/src/prelude_lower.isle
View File

@@ -308,23 +308,6 @@
;;;; Helpers for Working with Flags ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Reverse an IntCC flag.
(decl intcc_reverse (IntCC) IntCC)
(extern constructor intcc_reverse intcc_reverse)
;; Invert an IntCC flag.
(decl intcc_inverse (IntCC) IntCC)
(extern constructor intcc_inverse intcc_inverse)
;; Reverse an FloatCC flag.
(decl floatcc_reverse (FloatCC) FloatCC)
(extern constructor floatcc_reverse floatcc_reverse)
;; Invert an FloatCC flag.
(decl floatcc_inverse (FloatCC) FloatCC)
(extern constructor floatcc_inverse floatcc_inverse)
;; Newtype wrapper around `MInst` for instructions that are used for their
;; effect on flags.
;;