[MemorySSA] Fix phi insertion when inserting a def.

[asbirlea]

Summary

When inserting a Def, the current algorithm is walking edges backward
and inserting new Phis where needed. There may be additional Phis needed
in the IDF of the newly inserted Def and Phis.
Adding Phis in the IDF of the Def was added ina previous patch, but we
may also need other Phis in the IDF of the newly added Phis.

Resolves PR43320.

[george.burgess.iv]

thanks!

lib/Analysis/MemorySSAUpdater.cpp

343 ↗

(On Diff #220399)

will the compiler accept a const here? (and above)

[asbirlea]

Added const.

llvm/trunk/lib/Analysis/MemorySSAUpdater.cpp

if (!DefBeforeSameBlock) {
     // place, compute IDF and place phis.
     auto Iter = MD->getDefsIterator();
     ++Iter;
     auto IterEnd = MSSA->getBlockDefs(MD->getBlock())->end();
     if (Iter == IterEnd) {
       ForwardIDFCalculator IDFs(*MSSA->DT);
       SmallVector<BasicBlock *, 32> IDFBlocks;
       SmallPtrSet<BasicBlock *, 2> DefiningBlocks;
+      for (const auto &VH : InsertedPHIs)
+        if (const auto *RealPHI = cast_or_null<MemoryPhi>(VH))
+          DefiningBlocks.insert(RealPHI->getBlock());
       DefiningBlocks.insert(MD->getBlock());
       IDFs.setDefiningBlocks(DefiningBlocks);
       IDFs.calculate(IDFBlocks);
       SmallVector<AssertingVH<MemoryPhi>, 4> NewInsertedPHIs;
       for (auto *BBIDF : IDFBlocks) {
         auto *MPhi = MSSA->getMemoryAccess(BBIDF);
         if (!MPhi) {
           MPhi = MSSA->createMemoryPhi(BBIDF);

llvm/trunk/test/Analysis/MemorySSA/pr43320.ll

+; RUN: opt -licm -enable-mssa-loop-dependency -verify-memoryssa -S < %s | FileCheck %s
+; REQUIRES: asserts
+
+target datalayout = "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128"
+target triple = "aarch64-unknown-none-eabi"
+
+; CHECK-LABEL: @e()
+define void @e() {
+entry:
+  br label %g
+
+g:                                                ; preds = %cleanup, %entry
+  %0 = load i32, i32* null, align 4
+  %and = and i32 %0, undef
+  store i32 %and, i32* null, align 4
+  br i1 undef, label %if.end8, label %if.then
+
+if.then:                                          ; preds = %g
+  br i1 undef, label %k, label %cleanup
+
+k:                                                ; preds = %if.end8, %if.then
+  br i1 undef, label %if.end8, label %cleanup
+
+if.end8:                                          ; preds = %k, %g
+  br i1 undef, label %for.cond.preheader, label %k
+
+for.cond.preheader:                               ; preds = %if.end8
+  unreachable
+
+cleanup:                                          ; preds = %k, %if.then
+  br label %g
+}
+