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[RTG] Randomizer operations are not pure #10560

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[RTG] Randomizer operations are not pure #10560

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15 changes: 15 additions & 0 deletions include/circt/Dialect/RTG/IR/RTGOps.h
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Original file line number Diff line number Diff line change
Expand Up @@ -30,6 +30,21 @@
#include "mlir/Interfaces/InferTypeOpInterface.h"
#include "mlir/Interfaces/SideEffectInterfaces.h"

namespace circt {
namespace rtg {

/// A custom resource representing the RNG state. Operations that read from or
/// write to the RNG state should declare effects on this resource to prevent
/// CSE and DCE.
struct RNGStateResource
: public mlir::SideEffects::Resource::Base<RNGStateResource> {
StringRef getName() const final { return "RTGRNGStateResource"; }
bool isAddressable() const override { return false; }
};

} // namespace rtg
} // namespace circt

#define GET_OP_CLASSES
#include "circt/Dialect/RTG/IR/RTG.h.inc"

Expand Down
16 changes: 12 additions & 4 deletions include/circt/Dialect/RTG/IR/RTGOps.td
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Expand Up @@ -25,6 +25,10 @@ include "circt/Dialect/RTG/IR/RTGInterfaces.td"
include "circt/Dialect/RTG/IR/RTGISAAssemblyInterfaces.td"
include "circt/Dialect/Emit/EmitOpInterfaces.td"

// Resource representing the RNG state. Operations that read from or write to
// the RNG state should declare effects on this resource to prevent CSE and DCE.
def RNGStateResource : Resource<"RNGStateResource">;

// Base class for the operation in this dialect.
class RTGOp<string mnemonic, list<Trait> traits = []> :
Op<RTGDialect, mnemonic, traits>;
Expand Down Expand Up @@ -363,8 +367,8 @@ def SetCreateOp : RTGOp<"set_create", [Pure, SameTypeOperands]> {
}

def SetSelectRandomOp : RTGOp<"set_select_random", [
Pure,
TypesMatchWith<"output must be of the element type of input set",
MemoryEffects<[MemRead<RNGStateResource>, MemWrite<RNGStateResource>]>,
TypesMatchWith<"output must be of the element type of input set",
"set", "output",
"llvm::cast<rtg::SetType>($_self).getElementType()">
]> {
Expand Down Expand Up @@ -496,7 +500,7 @@ def BagCreateOp : RTGOp<"bag_create", [Pure, SameVariadicOperandSize]> {
}

def BagSelectRandomOp : RTGOp<"bag_select_random", [
Pure,
MemoryEffects<[MemRead<RNGStateResource>, MemWrite<RNGStateResource>]>,
TypesMatchWith<"output must be element type of input bag", "bag", "output",
"llvm::cast<rtg::BagType>($_self).getElementType()">
]> {
Expand Down Expand Up @@ -712,7 +716,9 @@ def TupleExtractOp : RTGOp<"tuple_extract", [

//===- Integer Operations -------------------------------------------------===//

def RandomNumberInRangeOp : RTGOp<"random_number_in_range", []> {
def RandomNumberInRangeOp : RTGOp<"random_number_in_range", [
MemoryEffects<[MemRead<RNGStateResource>, MemWrite<RNGStateResource>]>
]> {
let summary = "returns a number uniformly at random within the given range";
let description = [{
This operation computes a random number based on a uniform distribution
Expand Down Expand Up @@ -760,6 +766,8 @@ def ConstraintOp : RTGOp<"constraint", []> {

def RandomScopeOp : RTGOp<"random_scope", [
NoRegionArguments,
MemoryEffects<[MemRead<RNGStateResource>, MemWrite<RNGStateResource>]>,
RecursiveMemoryEffects,
SingleBlockImplicitTerminator<"rtg::YieldOp">,
]> {
let summary = "introduce a new scope for randomization";
Expand Down
54 changes: 53 additions & 1 deletion test/Dialect/RTG/IR/cse.mlir
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Expand Up @@ -7,11 +7,63 @@ rtg.sequence @seq0() attributes {rtg.some_attr} {
%str = rtg.constant "label_string" : !rtg.string
// CHECK-NEXT: rtg.label_unique_decl [[STR]]
// CHECK-NEXT: rtg.label_unique_decl [[STR]]
// They are DCE'd but not CSE'd
// They are DCE'd but not CSE'd
%2 = rtg.label_unique_decl %str
%3 = rtg.label_unique_decl %str
%4 = rtg.label_unique_decl %str
// CHECK-NEXT: rtg.label global
rtg.label global %2
rtg.label global %3
}

// CHECK-LABEL: rtg.sequence @setSelectRandom
rtg.sequence @setSelectRandom(%arg0: i32, %arg1: i32) {
// CHECK: [[SET:%.+]] = rtg.set_create %arg0, %arg1 : i32
%set = rtg.set_create %arg0, %arg1 : i32
// CHECK-NEXT: rtg.set_select_random [[SET]] : !rtg.set<i32>
// CHECK-NEXT: rtg.set_select_random [[SET]] : !rtg.set<i32>
// CHECK-NEXT: rtg.set_select_random [[SET]] : !rtg.set<i32>
Comment on lines +23 to +25
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@seldridge seldridge May 29, 2026

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Consider:

Suggested change
// CHECK-NEXT: rtg.set_select_random [[SET]] : !rtg.set<i32>
// CHECK-NEXT: rtg.set_select_random [[SET]] : !rtg.set<i32>
// CHECK-NEXT: rtg.set_select_random [[SET]] : !rtg.set<i32>
// CHECK-COUNT-3: rtg.set_select_random [[SET]] : !rtg.set<i32>
// CHECK-NOT: rtg.set_select_random [[SET]]

Same comment throughout.

// They are not CSE'd and not DCE'd
%0 = rtg.set_select_random %set : !rtg.set<i32>
%1 = rtg.set_select_random %set : !rtg.set<i32>
%2 = rtg.set_select_random %set : !rtg.set<i32>
}

// CHECK-LABEL: rtg.sequence @bagSelectRandom
rtg.sequence @bagSelectRandom(%arg0: i32, %arg1: i32, %arg2: index) {
// CHECK: [[BAG:%.+]] = rtg.bag_create (%arg2 x %arg0, %arg2 x %arg1) : i32
%bag = rtg.bag_create (%arg2 x %arg0, %arg2 x %arg1) : i32
// CHECK-NEXT: rtg.bag_select_random [[BAG]] : !rtg.bag<i32>
// CHECK-NEXT: rtg.bag_select_random [[BAG]] : !rtg.bag<i32>
// CHECK-NEXT: rtg.bag_select_random [[BAG]] : !rtg.bag<i32>
// They are not CSE'd and not DCE'd
%0 = rtg.bag_select_random %bag : !rtg.bag<i32>
%1 = rtg.bag_select_random %bag : !rtg.bag<i32>
%2 = rtg.bag_select_random %bag : !rtg.bag<i32>
}

// CHECK-LABEL: rtg.sequence @randomScope
rtg.sequence @randomScope() {
// CHECK: rtg.random_scope attributes {a}
// CHECK: rtg.random_scope attributes {b}
// CHECK: rtg.random_scope attributes {c}
// They are not CSE'd and not DCE'd
rtg.random_scope attributes {a} {}
rtg.random_scope attributes {b} {}
rtg.random_scope attributes {c} {}
}

// CHECK-LABEL: rtg.sequence @randomNumberInRange
rtg.sequence @randomNumberInRange() {
// CHECK: [[LOW:%.+]] = index.constant 0
// CHECK-NEXT: [[HIGH:%.+]] = index.constant 100
// CHECK-NEXT: rtg.random_number_in_range {{\[}}[[LOW]], [[HIGH]]{{\]}}
// CHECK-NEXT: rtg.random_number_in_range {{\[}}[[LOW]], [[HIGH]]{{\]}}
// CHECK-NEXT: rtg.random_number_in_range {{\[}}[[LOW]], [[HIGH]]{{\]}}
%low = index.constant 0
%high = index.constant 100
// They are not CSE'd and not DCE'd
%0 = rtg.random_number_in_range [%low, %high]
%1 = rtg.random_number_in_range [%low, %high]
%2 = rtg.random_number_in_range [%low, %high]
}
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