[RegisterBankInfo] Check that the mapping covers the interesting bits.

In the verify method of the ValueMapping class we used to check that the
mapping exactly matches the bits of the input value. This is problematic
for statically allocated mappings because we would need a different
mapping for each different size of the value that maps on one
instruction. For instance, with such scheme, we would need a different
mapping for a value of size 1, 5, 23 whereas they all end up on a 32-bit
wide instruction.

Therefore, change the verifier to check that the meaningful bits are
covered by the mapping instead of matching them.

llvm-svn: 282214

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h b/llvm/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
index 658f2c7..761f50f 100644 (file)
--- a/llvm/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
@@ -95,11 +95,12 @@ public:
     const PartialMapping *begin() const { return BreakDown; }
     const PartialMapping *end() const { return BreakDown + NumBreakDowns; }
 
-    /// Verify that this mapping makes sense for a value of \p ExpectedBitWidth.
+    /// Verify that this mapping makes sense for a value of
+    /// \p MeaningFulBitWidth.
     /// \note This method does not check anything when assertions are disabled.
     ///
     /// \return True is the check was successful.
-    bool verify(unsigned ExpectedBitWidth) const;
+    bool verify(unsigned MeaningFulBitWidth) const;
 
     /// Print this on dbgs() stream.
     void dump() const;

diff --git a/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp b/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
index 43a1262..291441a 100644 (file)
--- a/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
@@ -422,7 +422,7 @@ void RegisterBankInfo::PartialMapping::print(raw_ostream &OS) const {
     OS << "nullptr";
 }
 
-bool RegisterBankInfo::ValueMapping::verify(unsigned ExpectedBitWidth) const {
+bool RegisterBankInfo::ValueMapping::verify(unsigned MeaningFulBitWidth) const {
   assert(NumBreakDowns && "Value mapped nowhere?!");
   unsigned OrigValueBitWidth = 0;
   for (const RegisterBankInfo::PartialMapping &PartMap : *this) {
@@ -434,7 +434,8 @@ bool RegisterBankInfo::ValueMapping::verify(unsigned ExpectedBitWidth) const {
     OrigValueBitWidth =
         std::max(OrigValueBitWidth, PartMap.getHighBitIdx() + 1);
   }
-  assert(OrigValueBitWidth == ExpectedBitWidth && "BitWidth does not match");
+  assert(OrigValueBitWidth >= MeaningFulBitWidth &&
+         "Meaningful bits not covered by the mapping");
   APInt ValueMask(OrigValueBitWidth, 0);
   for (const RegisterBankInfo::PartialMapping &PartMap : *this) {
     // Check that the union of the partial mappings covers the whole value,