Fix ppc64le stack overflow from deep Sequential chains in graph checking#20028
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Fix ppc64le stack overflow from deep Sequential chains in graph checking#20028T-Gro wants to merge 4 commits into
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Long statement sequences parse into deeply right-nested SynExpr.Sequential chains. FileContentMapping.visitSynExpr walks them in CPS, and under BUILD_USING_MONO each visit runs inside a StackGuard that only checks room for one more frame. On ppc64le the larger stack frames deplete the stack between guard checks, causing the compiler to crash while building fsharp. Flatten the Sequential chain into a flat list and hand the per-element continuations to Continuation.concatenate, matching the existing handling for IfThenElse, Tuple and ArrayOrList. This halves the number of guarded frames for a chain and preserves the emitted entry order. Fixes dotnet#19988 Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
auduchinok
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Jul 3, 2026
Move the sequential-flattening logic into SyntaxTreeOps as flattenSequentials (with (|Sequentials|_|) as sugar over it), so FileContentMapping reuses it instead of a local copy and ParsedInput's duplicate is removed. The exhaustive match in visitSynExpr keeps the concrete SynExpr.Sequential case. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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Fixes #19988
Long statement sequences parse into deeply right-nested
SynExpr.Sequentialchains that
FileContentMapping.visitSynExprwalked with one nestedvisitper element. Under
BUILD_USING_MONOeachvisitruns inside aStackGuard,and ppc64le's large stack frames deplete the stack between guard checks.
Flattening the chain first — as already done for
IfThenElse— halves theguarded frames per chain and preserves the emitted entry order.