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Change effect for pause #8401

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Merged
tlively merged 1 commit into from
Feb 27, 2026
+34 −8
Merged

Change effect for pause #8401

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7 changes: 4 additions & 3 deletions src/ir/effects.h
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Original file line number Diff line number Diff line change
Expand Up @@ -644,9 +644,10 @@ class EffectAnalyzer {
parent.isAtomic = true;
}
void visitPause(Pause* curr) {
// It's not much of a problem if pause gets reordered with anything, but
// we don't want it to be removed entirely.
parent.isAtomic = true;
// We don't want this to be moved out of loops, but it doesn't otherwises
// matter much how it gets reordered. Say we transfer control as a coarse
// approximation of this.
parent.branchesOut = true;
}
void visitSIMDExtract(SIMDExtract* curr) {}
void visitSIMDReplace(SIMDReplace* curr) {}
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35 changes: 30 additions & 5 deletions test/lit/passes/licm.wast
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
;; NOTE: Assertions have been generated by update_lit_checks.py --all-items and should not be edited.

;; RUN: foreach %s %t wasm-opt --licm -S -o - | filecheck %s
;; RUN: foreach %s %t wasm-opt -all --licm -S -o - | filecheck %s

(module
(memory 10 20)
Expand All @@ -11,7 +11,7 @@

;; CHECK: (memory $0 10 20)

;; CHECK: (func $unreachable-get
;; CHECK: (func $unreachable-get (type $1)
;; CHECK-NEXT: (local $x i32)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (local.get $x)
Expand All @@ -35,7 +35,7 @@
)
)

;; CHECK: (func $unreachable-get-call (param $p i32)
;; CHECK: (func $unreachable-get-call (type $0) (param $p i32)
;; CHECK-NEXT: (local $x i32)
;; CHECK-NEXT: (loop $loop
;; CHECK-NEXT: (unreachable)
Expand All @@ -56,7 +56,7 @@
)
)

;; CHECK: (func $unreachable-get-store (param $p i32)
;; CHECK: (func $unreachable-get-store (type $0) (param $p i32)
;; CHECK-NEXT: (local $x i32)
;; CHECK-NEXT: (loop $loop
;; CHECK-NEXT: (unreachable)
Expand All @@ -78,5 +78,30 @@
)
)
)
)

;; CHECK: (func $pause (type $0) (param $p i32)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (i32.const 0)
;; CHECK-NEXT: )
;; CHECK-NEXT: (loop $loop
;; CHECK-NEXT: (nop)
;; CHECK-NEXT: (pause)
;; CHECK-NEXT: (drop
;; CHECK-NEXT: (i32.const 1)
;; CHECK-NEXT: )
;; CHECK-NEXT: (br $loop)
;; CHECK-NEXT: )
;; CHECK-NEXT: )
(func $pause (param $p i32)
;; We don't want pause to be moved out of loops. In principle we should be
;; able to move side-effect-free expressions back before the pause, but we
;; currently do not. Pause is rare and specialized enough that this shouldn't
;; be a problem.
(loop $loop
(drop (i32.const 0))
(pause)
(drop (i32.const 1))
(br $loop)
)
)
)
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