InstCombine: Fix a crash in PointerReplacer when constructing a new PHI (llvm#130256) (llvm#1144)

Author: changpeng

llvm/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp

@@ -374,7 +374,10 @@ void PointerReplacer::replace(Instruction *I) {
 
     IC.InsertNewInstWith(NewI, LT->getIterator());
     IC.replaceInstUsesWith(*LT, NewI);
-    WorkMap[LT] = NewI;
+    // LT has actually been replaced by NewI. It is useless to insert LT into
+    // the map. Instead, we insert NewI into the map to indicate this is the
+    // replacement (new value).
+    WorkMap[NewI] = NewI;
   } else if (auto *PHI = dyn_cast<PHINode>(I)) {
     Type *NewTy = getReplacement(PHI->getIncomingValue(0))->getType();
     auto *NewPHI = PHINode::Create(NewTy, PHI->getNumIncomingValues(),

llvm/test/Transforms/InstCombine/AMDGPU/phi-with-incoming-from-load.ll

@@ -0,0 +1,42 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -passes=instcombine -S -o - %s | FileCheck %s
+
+target triple = "amdgcn-amd-amdhsa"
+
+%double_double = type { double, double }
+
+declare void @llvm.memcpy.p0.p0.i64(ptr, ptr, i64, i1)
+
+define void @_test(ptr addrspace(4) byref(%double_double) align 8 %in)  {
+; CHECK-LABEL: define void @_test(
+; CHECK-SAME: ptr addrspace(4) byref([[DOUBLE_DOUBLE:%.*]]) align 8 [[IN:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    [[ALPHA_UNION:%.*]] = addrspacecast ptr addrspace(4) [[IN]] to ptr
+; CHECK-NEXT:    [[LOAD:%.*]] = load i8, ptr addrspace(5) null, align 1
+; CHECK-NEXT:    [[LOADEDV:%.*]] = trunc i8 [[LOAD]] to i1
+; CHECK-NEXT:    br i1 [[LOADEDV]], label %[[COND_END:.*]], label %[[COND_FALSE:.*]]
+; CHECK:       [[COND_FALSE]]:
+; CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr addrspace(4) [[IN]], align 8
+; CHECK-NEXT:    br label %[[COND_END]]
+; CHECK:       [[COND_END]]:
+; CHECK-NEXT:    [[COND1:%.*]] = phi ptr [ [[TMP0]], %[[COND_FALSE]] ], [ [[ALPHA_UNION]], %[[ENTRY]] ]
+; CHECK-NEXT:    call void @llvm.memcpy.p0.p0.i64(ptr noundef nonnull align 1 dereferenceable(16) poison, ptr noundef nonnull align 1 dereferenceable(16) [[COND1]], i64 16, i1 false)
+; CHECK-NEXT:    ret void
+;
+entry:
+  %coerce = alloca %double_double, align 8, addrspace(5)
+  %alpha_union = addrspacecast ptr addrspace(5) %coerce to ptr
+  call void @llvm.memcpy.p5.p4.i64(ptr addrspace(5) align 8 %coerce, ptr addrspace(4) align 8 %in, i64 16, i1 false)
+  %load1 = load i8, ptr addrspace(5) null, align 1
+  %loadedv = trunc i8 %load1 to i1
+  br i1 %loadedv, label %cond.end, label %cond.false
+
+cond.false:
+  %load2 = load ptr, ptr addrspace(5) %coerce, align 8
+  br label %cond.end
+
+cond.end:
+  %cond = phi ptr [ %load2, %cond.false ], [ %alpha_union, %entry ]
+  call void @llvm.memcpy.p0.p0.i64(ptr poison, ptr %cond, i64 16, i1 false)
+  ret void
+}