[llvm] r282214 - [RegisterBankInfo] Check that the mapping covers the interesting bits.

[Quentin Colombet via llvm-commits]

Author: qcolombet
Date: Thu Sep 22 19:14:34 2016
New Revision: 282214

URL: http://llvm.org/viewvc/llvm-project?rev=282214&view=rev
Log:
[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.

Modified:
    llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
    llvm/trunk/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp

Modified: llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h?rev=282214&r1=282213&r2=282214&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h (original)
+++ llvm/trunk/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h Thu Sep 22 19:14:34 2016
@@ -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;

Modified: llvm/trunk/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp?rev=282214&r1=282213&r2=282214&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp (original)
+++ llvm/trunk/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp Thu Sep 22 19:14:34 2016
@@ -422,7 +422,7 @@ void RegisterBankInfo::PartialMapping::p
     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::ver
     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,