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[LLHD] Allow projections across blocks in mem2reg #8855

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Merged
merged 1 commit into from
Aug 15, 2025
+28 −6
Merged

[LLHD] Allow projections across blocks in mem2reg #8855

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8 changes: 2 additions & 6 deletions lib/Dialect/LLHD/Transforms/Mem2Reg.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -770,15 +770,11 @@ void Promoter::findPromotableSlots() {
// Ignore uses outside of the region.
if (user->getParentRegion() != &region)
return true;
// Projection operations are okay as long as they are in the same block
// as any of their users.
// Projection operations are okay.
if (isa<SigArrayGetOp, SigExtractOp, SigStructExtractOp>(user)) {
for (auto *projectionUser : user->getUsers()) {
if (projectionUser->getBlock() != user->getBlock())
return false;
for (auto *projectionUser : user->getUsers())
if (checkedUsers.insert(projectionUser).second)
userWorklist.push_back(projectionUser);
}
projections.insert({user->getResult(0), operand});
return true;
}
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26 changes: 26 additions & 0 deletions test/Dialect/LLHD/Transforms/mem2reg.mlir
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Expand Up @@ -1093,3 +1093,29 @@ hw.module @DominanceTest2() {
}
hw.output
}

// CHECK-LABEL: @ProjectionAndDriveInDifferentBlocks
hw.module @ProjectionAndDriveInDifferentBlocks(in %u: !hw.struct<f: i42>, in %v: i42, in %q: i1) {
%0 = llhd.constant_time <0ns, 0d, 1e>
%a = llhd.sig %u : !hw.struct<f: i42>
// CHECK: llhd.process
llhd.process {
// CHECK-NOT: llhd.drv
llhd.drv %a, %u after %0 : !hw.inout<struct<f: i42>>
// CHECK-NOT: llhd.sig.struct_extract
%1 = llhd.sig.struct_extract %a["f"] : !hw.inout<struct<f: i42>>
// CHECK-NEXT: cf.br ^bb1
cf.br ^bb1
^bb1:
// CHECK-NEXT: ^bb1
// CHECK-NOT: llhd.drv
// CHECK-NEXT: [[EXT:%.+]] = hw.struct_extract %u["f"]
// CHECK-NEXT: [[MUX:%.+]] = comb.mux %q, %v, [[EXT]]
// CHECK-NEXT: [[INJ:%.+]] = hw.struct_inject %u["f"], [[MUX]]
llhd.drv %1, %v after %0 if %q : !hw.inout<i42>
// CHECK-NEXT: llhd.constant_time
// CHECK-NEXT: llhd.drv %a, [[INJ]]
// CHECK-NEXT: llhd.halt
llhd.halt
}
}