[SCEVExp] Check if getPtrToIntExpr resulted in CouldNotCompute.

This fixes a crash trying to use SCEVCouldNotCompute, if getPtrToIntExpr
failed.

Fixes llvm#155287

Author: fhahn

llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp

@@ -1239,10 +1239,13 @@ Value *SCEVExpander::tryToReuseLCSSAPhi(const SCEVAddRecExpr *S) {
     if (!isa<SCEVAddRecExpr>(ExitSCEV))
       continue;
     Type *PhiTy = PN.getType();
-    if (STy->isIntegerTy() && PhiTy->isPointerTy())
+    if (STy->isIntegerTy() && PhiTy->isPointerTy()) {
       ExitSCEV = SE.getPtrToIntExpr(ExitSCEV, STy);
-    else if (S->getType() != PN.getType())
+      if (isa<SCEVCouldNotCompute>(ExitSCEV))
+        continue;
+    } else if (S->getType() != PN.getType()) {
       continue;
+    }
 
     // Check if we can re-use the existing PN, by adjusting it with an expanded
     // offset, if the offset is simpler.

llvm/test/Transforms/LoopIdiom/reuse-lcssa-phi-scev-expansion.ll

@@ -1,6 +1,8 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
 ; RUN: opt -p loop-idiom -S %s | FileCheck %s
 
+target datalayout = "e-m:e-i64:64-i128:128-f80:128-n8:16:32:64-S128-ni:1-p2:32:8:8:32-ni:2"
+
 declare void @foo()
 declare void @bar()
 
@@ -160,3 +162,63 @@ loop.0.latch:
 exit:
   ret ptr %res
 }
+
+; Test case for https://github.com/llvm/llvm-project/issues/155287.
+; Make sure we don't crash when trying to construct a PtrToInt SCEV expression
+; results in SCEVCouldNotCompute.
+define void @phi_ptr_addressspace_ptrtoint_fail(ptr addrspace(1) %arg) {
+; CHECK-LABEL: define void @phi_ptr_addressspace_ptrtoint_fail(
+; CHECK-SAME: ptr addrspace(1) [[ARG:%.*]]) {
+; CHECK-NEXT:  [[BB:.*]]:
+; CHECK-NEXT:    br label %[[LOOP_1:.*]]
+; CHECK:       [[LOOP_1]]:
+; CHECK-NEXT:    [[IV_1:%.*]] = phi i64 [ 0, %[[BB]] ], [ [[ADD5:%.*]], %[[LOOP_1]] ]
+; CHECK-NEXT:    [[ADD5]] = add i64 [[IV_1]], 1
+; CHECK-NEXT:    [[GETELEMENTPTR:%.*]] = getelementptr i16, ptr addrspace(1) [[ARG]], i64 [[ADD5]]
+; CHECK-NEXT:    br i1 false, label %[[LOOP_1]], label %[[LOOP_2_PH:.*]]
+; CHECK:       [[LOOP_2_PH]]:
+; CHECK-NEXT:    [[IV_1_LCSSA1:%.*]] = phi i64 [ [[IV_1]], %[[LOOP_1]] ]
+; CHECK-NEXT:    [[IV_1_LCSSA:%.*]] = phi i64 [ [[IV_1]], %[[LOOP_1]] ]
+; CHECK-NEXT:    [[PHI:%.*]] = phi ptr addrspace(1) [ [[GETELEMENTPTR]], %[[LOOP_1]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = shl nuw nsw i64 [[IV_1_LCSSA1]], 2
+; CHECK-NEXT:    [[SCEVGEP:%.*]] = getelementptr i8, ptr addrspace(1) [[ARG]], i64 [[TMP0]]
+; CHECK-NEXT:    call void @llvm.memset.p1.i64(ptr addrspace(1) align 4 [[SCEVGEP]], i8 0, i64 8, i1 false)
+; CHECK-NEXT:    br label %[[LOOP_2_HEADER:.*]]
+; CHECK:       [[LOOP_2_HEADER]]:
+; CHECK-NEXT:    [[IV_2:%.*]] = phi i64 [ [[IV_1_LCSSA]], %[[LOOP_2_PH]] ], [ [[IV_2_NEXT:%.*]], %[[LOOP_2_LATCH:.*]] ]
+; CHECK-NEXT:    [[GREP_ARG:%.*]] = getelementptr i32, ptr addrspace(1) [[ARG]], i64 [[IV_2]]
+; CHECK-NEXT:    [[EC:%.*]] = icmp ult i64 [[IV_2]], 1
+; CHECK-NEXT:    br i1 [[EC]], label %[[LOOP_2_LATCH]], label %[[EXIT:.*]]
+; CHECK:       [[LOOP_2_LATCH]]:
+; CHECK-NEXT:    [[IV_2_NEXT]] = add i64 [[IV_2]], 1
+; CHECK-NEXT:    br label %[[LOOP_2_HEADER]]
+; CHECK:       [[EXIT]]:
+; CHECK-NEXT:    ret void
+;
+bb:
+  br label %loop.1
+
+loop.1:
+  %iv.1 = phi i64 [ 0, %bb ], [ %add5, %loop.1]
+  %add5 = add i64 %iv.1, 1
+  %getelementptr = getelementptr i16, ptr addrspace(1) %arg, i64 %add5
+  br i1 false, label %loop.1, label %loop.2.ph
+
+loop.2.ph:
+  %phi = phi ptr addrspace(1) [ %getelementptr, %loop.1]
+  br label %loop.2.header
+
+loop.2.header:
+  %iv.2 = phi i64 [ %iv.1, %loop.2.ph ], [ %iv.2.next, %loop.2.latch ]
+  %grep.arg = getelementptr i32, ptr addrspace(1) %arg, i64 %iv.2
+  store i32 0, ptr addrspace(1) %grep.arg, align 4
+  %ec = icmp ult i64 %iv.2, 1
+  br i1 %ec, label %loop.2.latch, label %exit
+
+loop.2.latch:
+  %iv.2.next = add i64 %iv.2, 1
+  br label %loop.2.header
+
+exit:
+  ret void
+}