[AssumptionCache] Do not track llvm.assume calls (PR49043)

This fixes PR49043 by invalidating the handle on RAUW. This will work
fine assuming all existing RAUW users add the new assumption to the
cache. That means, if a new llvm.assume call replaces an old one, you
need to add the new one now as a RAUW is not enough anymore.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D96208

Author: jdoerfert

llvm/include/llvm/Analysis/AssumptionCache.h

@@ -45,7 +45,7 @@ class AssumptionCache {
   enum : unsigned { ExprResultIdx = std::numeric_limits<unsigned>::max() };
 
   struct ResultElem {
-    WeakTrackingVH Assume;
+    WeakVH Assume;
 
     /// contains either ExprResultIdx or the index of the operand bundle
     /// containing the knowledge.

llvm/test/Transforms/GVNSink/assumption.ll

@@ -0,0 +1,32 @@
+; RUN: opt < %s -S -passes="print<assumptions>,gvn-sink,loop-unroll" -unroll-count=3 | FileCheck %s
+;
+; This crashed because the cached assumption was replaced and the replacement
+; was then in the cache twice.
+;
+; PR49043
+
+@g = external global i32
+
+define void @main() {
+bb:
+  %i1.i = load volatile i32, i32* @g
+  %i32.i = icmp eq i32 %i1.i, 0
+  call void @llvm.assume(i1 %i32.i) #3
+  br label %bb4.i
+
+bb4.i:                                            ; preds = %bb4.i, %bb
+  %i.i = load volatile i32, i32* @g
+  %i3.i = icmp eq i32 %i.i, 0
+  call void @llvm.assume(i1 %i3.i) #3
+  br label %bb4.i
+
+func_1.exit:                                      ; No predecessors!
+  unreachable
+}
+
+declare void @llvm.assume(i1)
+
+; CHECK:  call void @llvm.assume(
+; CHECK:  call void @llvm.assume(
+; CHECK:  call void @llvm.assume(
+