[ExportVerilog] Add disallowDeclAssignments lowering option. #9298
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This option controls whether assignments are emitted separately from declarations or inlined within them. When enabled, both continuous assignments and blocking assignments are always emitted separately rather than being inlined in net and variable declarations. This is useful for tools or coding styles that prefer explicit separation between declarations and assignments, improving and compatibility with certain linters or synthesis tools.
seldridge
approved these changes
Dec 3, 2025
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| // CHECK-LABEL: module test( | ||
| // DISALLOW-LABEL: module test( | ||
| hw.module @test(in %v: i1) { | ||
| // CHECK: wire w = v; | ||
| // DISALLOW: wire w; | ||
| // DISALLOW: assign w = v; | ||
| %w = sv.wire : !hw.inout<i1> | ||
| sv.assign %w, %v : i1 | ||
| // CHECK: initial begin | ||
| // DISALLOW: initial begin | ||
| sv.initial { | ||
| // CHECK: automatic logic l = v; | ||
| // DISALLOW: automatic logic l; | ||
| // DISALLOW-NEXT: l = v; | ||
| %l = sv.logic : !hw.inout<i1> | ||
| sv.bpassign %l, %v : i1 | ||
| } | ||
| } |
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Nit: you can collapse a lot of the checks down using --check-prefixes=CHECK,ALLOW and --check-prefixes=CHECK,DISALLOW to avoid some of the FileCheck duplication.
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| // DISALLOW: automatic logic l; | ||
| // DISALLOW-NEXT: l = v; |
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It is outside of my understanding of the spec to know if this makes sense. You may want to throw this at verilator --lint-only and make sure it's happy with it. I realize we generally avoid any use of automatic logic due to old problems with tools.
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Verilator is ok with this (and we've emitted this form when it's not possible to inline the assignment). automatic logic for sure has poor support generally so I feel we should flip the option at this point.
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This option controls whether assignments are emitted separately from declarations or inlined within them. When enabled, both continuous assignments and blocking assignments are always emitted separately rather than being inlined in net and variable declarations.
This is useful for tools or coding styles that prefer explicit separation between declarations and assignments, improving compatibility with certain linters or synthesis tools.
Fixes #9297.