[mlir] Make remove-dead-values pass remove blocks arguments first #165725
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@llvm/pr-subscribers-mlir @llvm/pr-subscribers-mlir-core Author: lonely eagle (linuxlonelyeagle) ChangesFix #163051. Full diff: https://github.com/llvm/llvm-project/pull/165725.diff 2 Files Affected:
diff --git a/mlir/lib/Transforms/RemoveDeadValues.cpp b/mlir/lib/Transforms/RemoveDeadValues.cpp
index e0c65b0e09774..dc3157bd7b5b2 100644
--- a/mlir/lib/Transforms/RemoveDeadValues.cpp
+++ b/mlir/lib/Transforms/RemoveDeadValues.cpp
@@ -731,7 +731,25 @@ static void processBranchOp(BranchOpInterface branchOp, RunLivenessAnalysis &la,
static void cleanUpDeadVals(RDVFinalCleanupList &list) {
LDBG() << "Starting cleanup of dead values...";
- // 1. Operations
+ // 1. Blocks
+ LDBG() << "Cleaning up " << list.blocks.size() << " block argument lists";
+ for (auto &b : list.blocks) {
+ // blocks that are accessed via multiple codepaths processed once
+ if (b.b->getNumArguments() != b.nonLiveArgs.size())
+ continue;
+ LDBG() << "Erasing " << b.nonLiveArgs.count()
+ << " non-live arguments from block: " << b.b;
+ // it iterates backwards because erase invalidates all successor indexes
+ for (int i = b.nonLiveArgs.size() - 1; i >= 0; --i) {
+ if (!b.nonLiveArgs[i])
+ continue;
+ LDBG() << " Erasing block argument " << i << ": " << b.b->getArgument(i);
+ b.b->getArgument(i).dropAllUses();
+ b.b->eraseArgument(i);
+ }
+ }
+
+ // 2. Operations
LDBG() << "Cleaning up " << list.operations.size() << " operations";
for (auto &op : list.operations) {
LDBG() << "Erasing operation: "
@@ -740,14 +758,14 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
op->erase();
}
- // 2. Values
+ // 3. Values
LDBG() << "Cleaning up " << list.values.size() << " values";
for (auto &v : list.values) {
LDBG() << "Dropping all uses of value: " << v;
v.dropAllUses();
}
- // 3. Functions
+ // 4. Functions
LDBG() << "Cleaning up " << list.functions.size() << " functions";
// Record which function arguments were erased so we can shrink call-site
// argument segments for CallOpInterface operations (e.g. ops using
@@ -769,7 +787,7 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
(void)f.funcOp.eraseResults(f.nonLiveRets);
}
- // 4. Operands
+ // 5. Operands
LDBG() << "Cleaning up " << list.operands.size() << " operand lists";
for (OperationToCleanup &o : list.operands) {
// Handle call-specific cleanup only when we have a cached callee reference.
@@ -811,7 +829,7 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
}
}
- // 5. Results
+ // 6. Results
LDBG() << "Cleaning up " << list.results.size() << " result lists";
for (auto &r : list.results) {
LDBG() << "Erasing " << r.nonLive.count()
@@ -820,24 +838,6 @@ static void cleanUpDeadVals(RDVFinalCleanupList &list) {
dropUsesAndEraseResults(r.op, r.nonLive);
}
- // 6. Blocks
- LDBG() << "Cleaning up " << list.blocks.size() << " block argument lists";
- for (auto &b : list.blocks) {
- // blocks that are accessed via multiple codepaths processed once
- if (b.b->getNumArguments() != b.nonLiveArgs.size())
- continue;
- LDBG() << "Erasing " << b.nonLiveArgs.count()
- << " non-live arguments from block: " << b.b;
- // it iterates backwards because erase invalidates all successor indexes
- for (int i = b.nonLiveArgs.size() - 1; i >= 0; --i) {
- if (!b.nonLiveArgs[i])
- continue;
- LDBG() << " Erasing block argument " << i << ": " << b.b->getArgument(i);
- b.b->getArgument(i).dropAllUses();
- b.b->eraseArgument(i);
- }
- }
-
// 7. Successor Operands
LDBG() << "Cleaning up " << list.successorOperands.size()
<< " successor operand lists";
diff --git a/mlir/test/Transforms/remove-dead-values.mlir b/mlir/test/Transforms/remove-dead-values.mlir
index e7304505c809e..8f56c656aa859 100644
--- a/mlir/test/Transforms/remove-dead-values.mlir
+++ b/mlir/test/Transforms/remove-dead-values.mlir
@@ -674,3 +674,18 @@ func.func @dead_value_loop_ivs_no_result(%lb: index, %ub: index, %step: index, %
}
return
}
+
+// -----
+
+// CHECK-LABEL: func @op_block_have_dead_arg
+func.func @op_block_have_dead_arg(%arg0: i64, %arg1: i64, %arg2: i64, %arg3: i1) {
+ omp.wsloop {
+ omp.loop_nest (%arg4) : i64 = (%arg0) to (%arg1) step (%arg2) {
+ cf.cond_br %arg3, ^bb1(%arg0 : i64), ^bb1(%arg1 : i64)
+ ^bb1(%0: i64):
+ omp.yield
+ }
+ }
+// CHECK-NEXT: return
+ return
+}
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ping for review @joker-eph, thank you. |
joker-eph
reviewed
Nov 5, 2025
| ^bb1(%0: i64): | ||
| omp.yield | ||
| } | ||
| } |
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Could we have a test using the test dialect? Or scf or something that is less likely to change than omp
joker-eph
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Nov 5, 2025
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LG, but I'd rather avoid using omp dialect in these tests.
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/55/builds/19677 Here is the relevant piece of the build log for the reference |
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cc: @joker-eph https://lab.llvm.org/buildbot/#/builders/169/builds/16768, should we revert it? |
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…arguments first" (#166746) Reverts llvm/llvm-project#165725. See https://lab.llvm.org/buildbot/#/builders/169/builds/16768,
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Fix #163051. Some Ops which have multiple blocks, before deleting the ops, first remove the dead parameters within its blocks.