[RegisterBankInfo] Relax the assert of having matching type sizes on default mappings

Instead of asserting that the type sizes are exactly equal, we check
that the new size is big enough to contain the original type.
We have to relax this constrain because, right now, we sometimes
specify that things that are smaller than a storage type are legal
instead of widening everything to the size of a storage type.
E.g., we say that G_AND s16 is legal and we map that on GPR32.

This is something we may revisit in the future (either by changing
the legalization process or keeping track separately of the storage
size and the size of the type), but let us reflect the reality of
the situation for now.

llvm-svn: 318587

1 files changed, 5 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp b/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
index 7353c2c010c..a474601d5f3 100644
--- a/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
@@ -441,7 +441,11 @@ void RegisterBankInfo::applyDefaultMapping(const OperandsMapper &OpdMapper) {
     LLT OrigTy = MRI.getType(OrigReg);
     LLT NewTy = MRI.getType(NewReg);
     if (OrigTy != NewTy) {
-      assert(OrigTy.getSizeInBits() == NewTy.getSizeInBits() &&
+      // The default mapping is not supposed to change the size of
+      // the storage. However, right now we don't necessarily bump all
+      // the types to storage size. For instance, we can consider
+      // s16 G_AND legal whereas the storage size is going to be 32.
+      assert(OrigTy.getSizeInBits() <= NewTy.getSizeInBits() &&
              "Types with difference size cannot be handled by the default "
              "mapping");
       DEBUG(dbgs() << "\nChange type of new opd from " << NewTy << " to "