[MIPS GlobalISel] Select sub

Lower G_USUBO and G_USUBE. Add narrowScalar for G_SUB.
Legalize and select G_SUB for MIPS 32.

Differential Revision: https://reviews.llvm.org/D53416

llvm-svn: 352351
diff --git a/llvm/lib/Target/Mips/MipsLegalizerInfo.cpp b/llvm/lib/Target/Mips/MipsLegalizerInfo.cpp
index ceab690..29c90ef 100644
--- a/llvm/lib/Target/Mips/MipsLegalizerInfo.cpp
+++ b/llvm/lib/Target/Mips/MipsLegalizerInfo.cpp
@@ -24,11 +24,11 @@
   const LLT s64 = LLT::scalar(64);
   const LLT p0 = LLT::pointer(0, 32);
 
-  getActionDefinitionsBuilder(G_ADD)
+  getActionDefinitionsBuilder({G_ADD, G_SUB})
       .legalFor({s32})
       .clampScalar(0, s32, s32);
 
-  getActionDefinitionsBuilder(G_UADDE)
+  getActionDefinitionsBuilder({G_UADDE, G_USUBO, G_USUBE})
       .lowerFor({{s32, s1}});
 
   getActionDefinitionsBuilder({G_LOAD, G_STORE})