Revert "Transform SCF IndexSwitch to nested If-Else (#7670)"

This reverts commit d379a35. This patch failed valgrind nightly regressions. I'm blamelessly reverting this to keep nightly clean.
llvm · Nov 26, 2024 · b987492 · b987492
1 parent 74598ea
commit b987492
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diff --git a/include/circt/Transforms/Passes.h b/include/circt/Transforms/Passes.h
@@ -46,7 +46,6 @@ std::unique_ptr<mlir::Pass> createInsertMergeBlocksPass();
 std::unique_ptr<mlir::Pass> createPrintOpCountPass();
 std::unique_ptr<mlir::Pass>
 createMemoryBankingPass(std::optional<unsigned> bankingFactor = std::nullopt);
-std::unique_ptr<mlir::Pass> createIndexSwitchToIfPass();
 
 //===----------------------------------------------------------------------===//
 // Utility functions.

diff --git a/include/circt/Transforms/Passes.td b/include/circt/Transforms/Passes.td
@@ -133,35 +133,4 @@ def MemoryBanking : Pass<"memory-banking", "::mlir::func::FuncOp"> {
   let dependentDialects = ["mlir::memref::MemRefDialect, mlir::scf::SCFDialect, mlir::affine::AffineDialect"];
 }
 
-def IndexSwitchToIf : Pass<"switch-to-if", "::mlir::ModuleOp"> {
-  let summary = "Index switch to if";
-  let description = [{
-      Transform `scf.index_switch` to a series of `scf.if` operations.
-      This is necessary for dialects that don't support switch statements, e.g., Calyx.
-      An example:
-      ```
-        %0 = scf.index_switch %cond -> i32
-          case 0 { ... }
-          case 1 { ... }
-          ...
-
-        =>
-
-        %c0 = arith.cmpi eq %0, 0
-        %c1 = arith.cmpi eq %0, 1
-        %0 = scf.if %c0 {
-         ...
-        } else {
-          %1 = scf.if %c1 {
-            ...
-          } else {
-            ...
-          }
-        }
-      ```
-  }];
-  let constructor = "circt::createIndexSwitchToIfPass()";
-  let dependentDialects = ["mlir::scf::SCFDialect"];
-}
-
 #endif // CIRCT_TRANSFORMS_PASSES
diff --git a/lib/Conversion/SCFToCalyx/SCFToCalyx.cpp b/lib/Conversion/SCFToCalyx/SCFToCalyx.cpp
@@ -1625,70 +1625,6 @@ class BuildParGroups : public calyx::FuncOpPartialLoweringPattern {
   }
 };
 
-class BuildSwitchGroups : public calyx::FuncOpPartialLoweringPattern {
-  using FuncOpPartialLoweringPattern::FuncOpPartialLoweringPattern;
-
-  LogicalResult
-  partiallyLowerFuncToComp(FuncOp funcOp,
-                           PatternRewriter &rewriter) const override {
-    LogicalResult res = success();
-    funcOp.walk([&](Operation *op) {
-      if (!isa<scf::IndexSwitchOp>(op))
-        return WalkResult::advance();
-
-      auto switchOp = cast<scf::IndexSwitchOp>(op);
-      auto loc = switchOp.getLoc();
-
-      Region &defaultRegion = switchOp.getDefaultRegion();
-      Operation *yieldOp = defaultRegion.front().getTerminator();
-      Value defaultResult = yieldOp->getOperand(0);
-
-      Value finalResult = defaultResult;
-      scf::IfOp prevIfOp = nullptr;
-
-      rewriter.setInsertionPointAfter(switchOp);
-      for (size_t i = 0; i < switchOp.getCases().size(); i++) {
-        auto caseValueInt = switchOp.getCases()[i];
-        if (prevIfOp)
-          rewriter.setInsertionPointToStart(&prevIfOp.getElseRegion().front());
-
-        Value caseValue = rewriter.create<ConstantIndexOp>(loc, caseValueInt);
-        Value cond = rewriter.create<CmpIOp>(
-            loc, CmpIPredicate::eq, *switchOp.getODSOperands(0).begin(),
-            caseValue);
-
-        auto ifOp = rewriter.create<scf::IfOp>(loc, switchOp.getResultTypes(),
-                                               cond, /*hasElseRegion=*/true);
-
-        Region &caseRegion = switchOp.getCaseRegions()[i];
-        IRMapping mapping;
-        Block &emptyThenBlock = ifOp.getThenRegion().front();
-        emptyThenBlock.erase();
-        caseRegion.cloneInto(&ifOp.getThenRegion(), mapping);
-
-        if (i == switchOp.getCases().size() - 1) {
-          rewriter.setInsertionPointToEnd(&ifOp.getElseRegion().front());
-          rewriter.create<scf::YieldOp>(loc, defaultResult);
-        }
-
-        if (prevIfOp) {
-          rewriter.setInsertionPointToEnd(&prevIfOp.getElseRegion().front());
-          rewriter.create<scf::YieldOp>(loc, ifOp.getResult(0));
-        }
-
-        if (i == 0)
-          finalResult = ifOp.getResult(0);
-        prevIfOp = ifOp;
-      }
-
-      rewriter.replaceOp(switchOp, finalResult);
-
-      return WalkResult::advance();
-    });
-    return res;
-  }
-};
-
 /// Builds a control schedule by traversing the CFG of the function and
 /// associating this with the previously created groups.
 /// For simplicity, the generated control flow is expanded for all possible
@@ -2465,10 +2401,6 @@ void SCFToCalyxPass::runOnOperation() {
   addOncePattern<BuildParGroups>(loweringPatterns, patternState, funcMap,
                                  *loweringState);
 
-  /// This pattern converts all scf.IndexSwitchOps to nested if-elses.
-  addOncePattern<BuildSwitchGroups>(loweringPatterns, patternState, funcMap,
-                                    *loweringState);
-
   /// This pattern converts all index typed values to an i32 integer.
   addOncePattern<calyx::ConvertIndexTypes>(loweringPatterns, patternState,
                                            funcMap, *loweringState);

diff --git a/lib/Transforms/CMakeLists.txt b/lib/Transforms/CMakeLists.txt
@@ -6,7 +6,6 @@ add_circt_library(CIRCTTransforms
   InsertMergeBlocks.cpp
   PrintOpCount.cpp
   MemoryBanking.cpp
-  IndexSwitchToIf.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${CIRCT_MAIN_INCLUDE_DIR}/circt/Transforms
@@ -20,7 +19,6 @@ add_circt_library(CIRCTTransforms
   MLIRFuncDialect
   MLIRIR
   MLIRMemRefDialect
-  MLIRSCFDialect
   MLIRSupport
   MLIRTransforms
   MLIRAffineDialect

diff --git a/lib/Transforms/IndexSwitchToIf.cpp b/lib/Transforms/IndexSwitchToIf.cpp
diff --git a/test/Transforms/switch-to-if.mlir b/test/Transforms/switch-to-if.mlir