[PATCH] Bug 20557 - bogus cpu parameter crashes llc

[Oleg Ranevskyy]

Hi HaoLiu,

Hi Hao,

Would you be able to find some time and review this simple correction that we discussed previously, please?
Thank you.

**Problem summary:**

Regression caused by http://reviews.llvm.org/D4322.
Llc crashes when compiling the attached file if -march=aarch64 and -mcpu specifies a cpu that is invalid for this architecture.

The problem is with v1f32 type. According to //AArch64TargetLowering::getPreferredVectorAction// this vector type should be widened on aarch64.

If a bogus CPU is passed to llc, v2f32 is not added to the legal types list.
Because of that, v1f32 fails to be widened, so //TargetLoweringBase::computeRegisterProperties()// falls through to the next switch-case branch, which sets the preferred type action to //TypeSplitVector//. This means we are trying to split one element vector. This triggers the assert in //VectorType::get//. The same applies to other 1-sized vector types listed in //getPreferredVectorAction//: v1i8, v1i16 and v1i32.

**Fix summary:**

If the preferred action for a one element vector is neither //TypeSplitVector// nor //TypeScalarizeVector// and it fails to be applied, then the action is set to //TypeScalarizeVector// instead of //TypeSplitVector//.

http://reviews.llvm.org/D5021

Files:
  lib/CodeGen/TargetLoweringBase.cpp

Index: lib/CodeGen/TargetLoweringBase.cpp
===================================================================
--- lib/CodeGen/TargetLoweringBase.cpp
+++ lib/CodeGen/TargetLoweringBase.cpp
@@ -1179,8 +1179,11 @@
       if (NVT == VT) {
         // Type is already a power of 2.  The default action is to split.
         TransformToType[i] = MVT::Other;
-        if (PreferredAction == TypeScalarizeVector)
+        if (   PreferredAction == TypeScalarizeVector
+            || VT.getVectorNumElements() == 1)
+        {
           ValueTypeActions.setTypeAction(VT, TypeScalarizeVector);
+        }
         else
           ValueTypeActions.setTypeAction(VT, TypeSplitVector);
       } else {
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