CodeGenPrep: fall back to MVT::Other if instruction's type isn't an EVT.

The test being performed is just an approximation anyway, so it really
shouldn't crash when things don't go entirely as expected.

Should fix PR20474.

llvm-svn: 214177

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -662,10 +662,13 @@ SinkShiftAndTruncate(BinaryOperator *ShiftI, Instruction *User, ConstantInt *CI,
     if (!ISDOpcode)
       continue;
 
-    // If the use is actually a legal node, there will not be an implicit
-    // truncate.
+    // If the use is actually a legal node, there will not be an
+    // implicit truncate.
+    // FIXME: always querying the result type is just an
+    // approximation; some nodes' legality is determined by the
+    // operand or other means. There's no good way to find out though.
     if (TLI.isOperationLegalOrCustom(ISDOpcode,
-                                     EVT::getEVT(TruncUser->getType())))
+                                     EVT::getEVT(TruncUser->getType(), true)))
       continue;
 
     // Don't bother for PHI nodes.

llvm/test/Transforms/CodeGenPrepare/AArch64/lit.local.cfg

@@ -0,0 +1,3 @@
+if not 'AArch64' in config.root.targets:
+    config.unsupported = True
+

llvm/test/Transforms/CodeGenPrepare/AArch64/trunc-weird-user.ll

@@ -0,0 +1,17 @@
+; RUN: opt -S -codegenprepare -mtriple=arm64-apple-ios7.0 %s | FileCheck %s
+
+%foo = type { i8 }
+
+define %foo @test_merge(i32 %in) {
+; CHECK-LABEL: @test_merge
+
+  ; CodeGenPrepare was requesting the EVT for { i8 } to determine
+  ; whether the insertvalue user of the trunc was legal. This
+  ; asserted.
+
+; CHECK: insertvalue %foo undef, i8 %byte, 0
+  %lobit = lshr i32 %in, 31
+  %byte = trunc i32 %lobit to i8
+  %struct = insertvalue %foo undef, i8 %byte, 0
+  ret %"foo" %struct
+}