ZJIT: Refine effects for CheckInterrupts to InterruptFlag|Control (ruby#16240)

CheckInterrupts only reads ec->interrupt_flag and conditionally
side-exits — it doesn't touch PatchPoint invariants or the allocator.
Add an InterruptFlag leaf under Memory in the abstract heap DAG and
narrow CheckInterrupts from Any to read(InterruptFlag)|write(Control).

This lets remove_redundant_patch_points see through CheckInterrupts,
eliminating duplicate PatchPoints that were previously separated by
an interrupt check.

Author: rwstauner

zjit/src/hir.rs

@@ -1241,7 +1241,7 @@ impl Insn {
             Insn::SideExit { .. } => effects::Any,
             Insn::IncrCounter(_) => Effect::read_write(abstract_heaps::Empty, abstract_heaps::Other),
             Insn::IncrCounterPtr { .. } => Effect::read_write(abstract_heaps::Empty, abstract_heaps::Other),
-            Insn::CheckInterrupts { .. } => effects::Any,
+            Insn::CheckInterrupts { .. } => Effect::read_write(abstract_heaps::InterruptFlag, abstract_heaps::Control),
             Insn::InvokeProc { .. } => effects::Any,
             Insn::RefineType { .. } => effects::Empty,
             Insn::HasType { .. } => effects::Empty,

zjit/src/hir/opt_tests.rs

@@ -623,9 +623,6 @@ mod hir_opt_tests {
           v60:TrueClass = Const Value(true)
           IncrCounter inline_cfunc_optimized_send_count
           CheckInterrupts
-          v23:Fixnum[2] = Const Value(2)
-          v25:Fixnum[2] = Const Value(2)
-          PatchPoint MethodRedefined(Integer@0x1000, <=@0x1008, cme:0x1010)
           v62:TrueClass = Const Value(true)
           IncrCounter inline_cfunc_optimized_send_count
           CheckInterrupts
@@ -697,9 +694,6 @@ mod hir_opt_tests {
           v60:TrueClass = Const Value(true)
           IncrCounter inline_cfunc_optimized_send_count
           CheckInterrupts
-          v23:Fixnum[2] = Const Value(2)
-          v25:Fixnum[2] = Const Value(2)
-          PatchPoint MethodRedefined(Integer@0x1000, >=@0x1008, cme:0x1010)
           v62:TrueClass = Const Value(true)
           IncrCounter inline_cfunc_optimized_send_count
           CheckInterrupts

zjit/src/hir_effect/gen_hir_effect.rb

@@ -49,6 +49,7 @@ def to_graphviz effect, f
 control = any.subeffect 'Control'
 memory = any.subeffect 'Memory'
 patch_point = any.subeffect 'PatchPoint'
+interrupt_flag = memory.subeffect 'InterruptFlag'
 other = memory.subeffect 'Other'
 frame = memory.subeffect 'Frame'
 pc = frame.subeffect 'PC'