[llvm] [ValueTracking] Add missing check for two-value PN recurrance matching (PR #152700)

[Nikita Popov via llvm-commits]

================
@@ -1310,6 +1310,37 @@ TEST_F(ValueTrackingTest, MatchBinaryIntrinsicRecurrenceNegativeFSHR) {
   EXPECT_FALSE(matchSimpleBinaryIntrinsicRecurrence(II, PN, Init, OtherOp));
 }
 
+TEST_F(ValueTrackingTest, MatchBinaryIntrinsicRecurrenceNonTwoOperand) {
+  auto M = parseModule(R"(
+    declare noundef i32 @llvm.nvvm.read.ptx.sreg.nctaid.x()
+    declare i32 @llvm.umin.i32(i32, i32)
+
+    define void @foo(i32 %arg) {
+    bb:
+      br i1 false, label %bb1, label %bb2
+
+    bb1:                                              ; preds = %bb
+      br label %bb3
+
+    bb2:                                              ; preds = %bb
+      %i = tail call noundef i32 @llvm.nvvm.read.ptx.sreg.nctaid.x()
+      br label %bb3
+
+    bb3:                                              ; preds = %bb2, %bb1
+      %i4 = phi i32 [ 0, %bb1 ], [ %i, %bb2 ]
+      %i6 = tail call noundef i32 @llvm.umin.i32(i32 %i4, i32 %arg)
+      ret void
+    }
+  )");
----------------
nikic wrote:

Wouldn't this reliably reproduce the issue, even in a lit test?
```
define i32 @foo(i1 %c, i32 %arg) {
entry:
  %i = call i32 @llvm.nvvm.read.ptx.sreg.nctaid.x()
  br i1 %c, label %bb.1, label %bb.2
bb.1:
  br label %bb.2
bb.2:
  %phi = phi i32 [ %i, %entry ], [ 0, %bb.1 ]
  %res = call i32 @llvm.umin.i32(i32 %phi, i32 %arg)
  ret i32 %res
}
```

https://github.com/llvm/llvm-project/pull/152700