[llvm] [Analysis] Avoid running transform passes that have just been run (PR #112092)

[Yingwei Zheng via llvm-commits]

================
@@ -0,0 +1,51 @@
+//===- LastRunTrackingAnalysis.cpp - Avoid running redundant pass -*- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This is an analysis pass to track a set of passes that have been run, so that
+// we can avoid running a pass again if there is no change since the last run of
+// the pass.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/LastRunTrackingAnalysis.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Support/CommandLine.h"
+
+using namespace llvm;
+
+#define DEBUG_TYPE "last-run-tracking"
+STATISTIC(NumSkippedPasses, "Number of skipped passes");
+STATISTIC(NumLRTQueries, "Number of LastRunTracking queries");
+
+static cl::opt<bool>
+    DisableLastRunTracking("disable-last-run-tracking", cl::Hidden,
+                           cl::desc("Disable last run tracking"),
+                           cl::init(false));
+
+bool LastRunTrackingInfo::shouldSkipImpl(PassID ID, OptionPtr Ptr) const {
+  if (DisableLastRunTracking)
+    return false;
+  ++NumLRTQueries;
+  auto Iter = TrackedPasses.find(ID);
----------------
dtcxzyw wrote:

SimplifyCFGPass runs with params in the `default<O3>` pipeline:
```
SimplifyCFGPass<bonus-inst-threshold=1;no-forward-switch-cond;no-switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;no-sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>
; no-switch-range-to-icmp -> switch-range-to-icmp
SimplifyCFGPass<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;no-sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>
SimplifyCFGPass<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;no-sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>
SimplifyCFGPass<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;no-sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>
SimplifyCFGPass<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;no-sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>
; no-hoist-common-insts -> hoist-common-insts, no-sink-common-insts -> sink-common-insts
SimplifyCFGPass<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>
; no-forward-switch-cond -> forward-switch-cond, no-switch-to-lookup -> switch-to-lookup, keep-loops -> no-keep-loops
SimplifyCFGPass<bonus-inst-threshold=1;forward-switch-cond;switch-range-to-icmp;switch-to-lookup;no-keep-loops;hoist-common-insts;no-hoist-loads-stores-with-cond-faulting;sink-common-insts;speculate-blocks;simplify-cond-branch;no-speculate-unpredictables>
; forward-switch-cond -> no-forward-switch-cond, hoist-common-insts -> no-hoist-common-insts, sink-common-insts -> no-sink-common-insts, no-hoist-loads-stores-with-cond-faulting -> hoist-loads-stores-with-cond-faulting
SimplifyCFGPass<bonus-inst-threshold=1;no-forward-switch-cond;switch-range-to-icmp;no-switch-to-lookup;keep-loops;no-hoist-common-insts;hoist-loads-stores-with-cond-faulting;no-sink-common-insts;speculate-blocks;simplify-cond-branch;speculate-unpredictables>
```
I cannot imagine we can benefit from a more fine-grained caching scheme. The `isCompatibleWith` interface should be enough.



https://github.com/llvm/llvm-project/pull/112092