Revert "Fix PR18361: Invalidate LoopDispositions after LoopSimplify hoists things."

This commit was the source of crasher PR18384:

While deleting: label %for.cond127
An asserting value handle still pointed to this value!
UNREACHABLE executed at llvm/lib/IR/Value.cpp:671!

Reverting to get the builders green, feel free to re-land after fixing up.
(Renato has a handy isolated repro if you need it.)

This reverts commit r198478.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198503 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Analysis/ScalarEvolution.h

@@ -784,13 +784,6 @@ namespace llvm {
     /// disconnect it from a def-use chain linking it to a loop.
     void forgetValue(Value *V);
 
-    /// \brief Called when the client has changed the disposition of values in
-    /// this loop.
-    ///
-    /// We don't have a way to invalidate per-loop dispositions. Clear and
-    /// recompute is simpler.
-    void forgetLoopDispositions(const Loop *L) { LoopDispositions.clear(); }
-
     /// GetMinTrailingZeros - Determine the minimum number of zero bits that S
     /// is guaranteed to end in (at every loop iteration).  It is, at the same
     /// time, the minimum number of times S is divisible by 2.  For example,

lib/Transforms/Utils/LoopSimplify.cpp

@@ -309,7 +309,6 @@ ReprocessLoop:
       // Attempt to hoist out all instructions except for the
       // comparison and the branch.
       bool AllInvariant = true;
-      bool AnyInvariant = false;
       for (BasicBlock::iterator I = ExitingBlock->begin(); &*I != BI; ) {
         Instruction *Inst = I++;
         // Skip debug info intrinsics.
@@ -317,26 +316,12 @@ ReprocessLoop:
           continue;
         if (Inst == CI)
           continue;
-        if (!L->makeLoopInvariant(Inst, AnyInvariant,
+        if (!L->makeLoopInvariant(Inst, Changed,
                                   Preheader ? Preheader->getTerminator() : 0)) {
           AllInvariant = false;
           break;
         }
       }
-      if (AnyInvariant) {
-        Changed = true;
-        // If any reachable control flow within this loop has changed, notify
-        // ScalarEvolution. Currently assume the parent loop doesn't change
-        // (spliting edges doesn't count). If blocks, CFG edges, or other values
-        // in the parent loop change, then we need call to forgetLoop() for the
-        // parent instead.
-        if (SE) {
-          SE->forgetLoop(L);
-          // The loop disposition of all SCEV expressions that depend on any
-          // hoisted values have also changed.
-          SE->forgetLoopDispositions(L);
-        }
-      }
       if (!AllInvariant) continue;
 
       // The block has now been cleared of all instructions except for
@@ -349,6 +334,14 @@ ReprocessLoop:
       DEBUG(dbgs() << "LoopSimplify: Eliminating exiting block "
                    << ExitingBlock->getName() << "\n");
 
+      // If any reachable control flow within this loop has changed, notify
+      // ScalarEvolution. Currently assume the parent loop doesn't change
+      // (spliting edges doesn't count). If blocks, CFG edges, or other values
+      // in the parent loop change, then we need call to forgetLoop() for the
+      // parent instead.
+      if (SE)
+        SE->forgetLoop(L);
+
       assert(pred_begin(ExitingBlock) == pred_end(ExitingBlock));
       Changed = true;
       LI->removeBlock(ExitingBlock);

test/Transforms/LoopSimplify/ashr-crash.ll

@@ -1,80 +0,0 @@
-; RUN: opt -basicaa -loop-rotate -licm -instcombine -indvars -loop-unroll -S %s | FileCheck %s
-;
-; PR18361: ScalarEvolution::getAddRecExpr():
-;          Assertion `isLoopInvariant(Operands[i],...
-;
-; After a series of loop optimizations, SCEV's LoopDispositions grow stale.
-; In particular, LoopSimplify hoists %cmp4, resulting in this SCEV for %add:
-; {(zext i1 %cmp4 to i32),+,1}<nw><%for.cond1.preheader>
-;
-; When recomputing the SCEV for %ashr, we truncate the operands to get:
-; (zext i1 %cmp4 to i16)
-;
-; This SCEV was never mapped to a value so never invalidated. It's
-; loop disposition is still marked as non-loop-invariant, which is
-; inconsistent with the AddRec.
-
-target datalayout = "e-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64-apple-macosx"
-
-@d = common global i32 0, align 4
-@a = common global i32 0, align 4
-@c = common global i32 0, align 4
-@b = common global i32 0, align 4
-
-; Check that the def-use chain that leads to the bad SCEV is still
-; there, and part of it is hoisted to the entry block.
-;
-; CHECK-LABEL: @foo
-; CHECK-LABEL: entry:
-; CHECK: %cmp4
-; CHECK-LABEL: for.cond1.preheader:
-; CHECK-LABEL: for.body3:
-; CHECK: %1 = zext i1 %cmp4 to i32
-; CHECK: %xor = xor i32 %1, 1
-define void @foo() {
-entry:
-  br label %for.cond
-
-for.cond:                                         ; preds = %for.inc7, %entry
-  %storemerge = phi i32 [ 0, %entry ], [ %inc8, %for.inc7 ]
-  %f.0 = phi i32 [ undef, %entry ], [ %f.1, %for.inc7 ]
-  store i32 %storemerge, i32* @d, align 4
-  %cmp = icmp slt i32 %storemerge, 1
-  br i1 %cmp, label %for.cond1, label %for.end9
-
-for.cond1:                                        ; preds = %for.cond, %for.body3
-  %storemerge1 = phi i32 [ %inc, %for.body3 ], [ 0, %for.cond ]
-  %f.1 = phi i32 [ %xor, %for.body3 ], [ %f.0, %for.cond ]
-  store i32 %storemerge1, i32* @a, align 4
-  %cmp2 = icmp slt i32 %storemerge1, 1
-  br i1 %cmp2, label %for.body3, label %for.inc7
-
-for.body3:                                        ; preds = %for.cond1
-  %0 = load i32* @c, align 4
-  %cmp4 = icmp sge i32 %storemerge1, %0
-  %conv = zext i1 %cmp4 to i32
-  %1 = load i32* @d, align 4
-  %add = add nsw i32 %conv, %1
-  %sext = shl i32 %add, 16
-  %conv6 = ashr exact i32 %sext, 16
-  %xor = xor i32 %conv6, 1
-  %inc = add nsw i32 %storemerge1, 1
-  br label %for.cond1
-
-for.inc7:                                         ; preds = %for.cond1
-  %2 = load i32* @d, align 4
-  %inc8 = add nsw i32 %2, 1
-  br label %for.cond
-
-for.end9:                                         ; preds = %for.cond
-  %cmp10 = icmp sgt i32 %f.0, 0
-  br i1 %cmp10, label %if.then, label %if.end
-
-if.then:                                          ; preds = %for.end9
-  store i32 0, i32* @b, align 4
-  br label %if.end
-
-if.end:                                           ; preds = %if.then, %for.end9
-  ret void
-}