[GlobalISel] Make multi-step legalization work.

In r301116, a custom lowering needed to be introduced to be able to
legalize 8 and 16-bit divisions on ARM targets without a division
instruction, since 2-step legalization (WidenScalar from 8 bit to 32
bit, then Libcall the 32-bit division) doesn't work.

This fixes this and makes this kind of multi-step legalization, where
first the size of the type needs to be changed and then some action is
needed that doesn't require changing the size of the type,
straighforward to specify.

Differential Revision: https://reviews.llvm.org/D32529

llvm-svn: 306806

1 files changed, 15 insertions, 11 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
index b8b820341a2..7e957590ede 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerInfo.cpp
@@ -178,19 +178,23 @@ Optional<LLT> LegalizerInfo::findLegalType(const InstrAspect &Aspect,
   case Libcall:
   case Custom:
     return Aspect.Type;
-  case NarrowScalar:
-    return findLegalType(Aspect,
-                         [](LLT Ty) -> LLT { return Ty.halfScalarSize(); });
-  case WidenScalar:
-    return findLegalType(Aspect, [](LLT Ty) -> LLT {
+  case NarrowScalar: {
+    return findLegalizableSize(
+        Aspect, [&](LLT Ty) -> LLT { return Ty.halfScalarSize(); });
+  }
+  case WidenScalar: {
+    return findLegalizableSize(Aspect, [&](LLT Ty) -> LLT {
       return Ty.getSizeInBits() < 8 ? LLT::scalar(8) : Ty.doubleScalarSize();
     });
-  case FewerElements:
-    return findLegalType(Aspect,
-                         [](LLT Ty) -> LLT { return Ty.halfElements(); });
-  case MoreElements:
-    return findLegalType(Aspect,
-                         [](LLT Ty) -> LLT { return Ty.doubleElements(); });
+  }
+  case FewerElements: {
+    return findLegalizableSize(
+        Aspect, [&](LLT Ty) -> LLT { return Ty.halfElements(); });
+  }
+  case MoreElements: {
+    return findLegalizableSize(
+        Aspect, [&](LLT Ty) -> LLT { return Ty.doubleElements(); });
+  }
   }
 }