[globalisel][aarch64] Fix unintended assumptions about PartialMappingIdx. NFC.

Summary:
This is NFC but prevents assertions when PartialMappingIdx is tablegen-erated.
The assumptions were:
1) FirstGPR is 0
2) FirstGPR is the first of the First* enumerators.

GPR32 is changed to 1 to demonstrate that assumption #1 is fixed. #2 will
be covered by a subsequent patch that tablegen-erates information and swaps
the order of GPR and FPR as a side effect.

Depends on D27336

Reviewers: ab, t.p.northover, qcolombet

Subscribers: aemerson, rengolin, vkalintiris, dberris, rovka, llvm-commits

Differential Revision: https://reviews.llvm.org/D27337

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@288812 91177308-0d34-0410-b5e6-96231b3b80d8

Author: dsandersllvm

lib/Target/AArch64/AArch64GenRegisterBankInfo.def

@@ -27,7 +27,7 @@ RegisterBank *RegBanks[] = {&GPRRegBank, &FPRRegBank, &CCRRegBank};
 // PartialMappings.
 enum PartialMappingIdx {
   PMI_None = -1,
-  PMI_GPR32 = 0,
+  PMI_GPR32 = 1,
   PMI_GPR64,
   PMI_FPR32,
   PMI_FPR64,
@@ -137,10 +137,11 @@ const RegisterBankInfo::ValueMapping *
 getValueMapping(PartialMappingIdx RBIdx, unsigned Size) {
   assert(RBIdx != PartialMappingIdx::PMI_None && "No mapping needed for that");
   unsigned ValMappingIdx = First3OpsIdx +
-                      (RBIdx + getRegBankBaseIdxOffset(Size)) *
-                          ValueMappingIdx::DistanceBetweenRegBanks;
-    assert(ValMappingIdx >= AArch64::First3OpsIdx &&
-           ValMappingIdx <= AArch64::Last3OpsIdx && "Mapping out of bound");
+                           (RBIdx - AArch64::PartialMappingIdx::PMI_Min +
+                            getRegBankBaseIdxOffset(Size)) *
+                               ValueMappingIdx::DistanceBetweenRegBanks;
+  assert(ValMappingIdx >= AArch64::First3OpsIdx &&
+         ValMappingIdx <= AArch64::Last3OpsIdx && "Mapping out of bound");
 
   return &ValMappings[ValMappingIdx];
 }
@@ -160,7 +161,7 @@ getCopyMapping(bool DstIsGPR, bool SrcIsGPR, unsigned Size) {
   assert(Size <= 64 && "GPR cannot handle that size");
   unsigned ValMappingIdx =
       FirstCrossRegCpyIdx +
-      (DstRBIdx - PMI_FirstGPR + getRegBankBaseIdxOffset(Size)) *
+      (DstRBIdx - PMI_Min + getRegBankBaseIdxOffset(Size)) *
           ValueMappingIdx::DistanceBetweenCrossRegCpy;
   assert(ValMappingIdx >= AArch64::FirstCrossRegCpyIdx &&
          ValMappingIdx <= AArch64::LastCrossRegCpyIdx &&

lib/Target/AArch64/AArch64RegisterBankInfo.cpp

@@ -115,8 +115,9 @@ AArch64RegisterBankInfo::AArch64RegisterBankInfo(const TargetRegisterInfo &TRI)
 #define CHECK_PARTIALMAP(Idx, ValStartIdx, ValLength, RB)                      \
   do {                                                                         \
     const PartialMapping &Map =                                                \
-        AArch64::PartMappings[AArch64::PartialMappingIdx::Idx];                \
-    (void) Map;                                                                \
+        AArch64::PartMappings[AArch64::PartialMappingIdx::Idx -                \
+                              AArch64::PartialMappingIdx::PMI_Min];            \
+    (void)Map;                                                                 \
     assert(Map.StartIdx == ValStartIdx && Map.Length == ValLength &&           \
            Map.RegBank == &RB && #Idx " is incorrectly initialized");          \
   } while (0)
@@ -132,12 +133,13 @@ AArch64RegisterBankInfo::AArch64RegisterBankInfo(const TargetRegisterInfo &TRI)
 // Check value mapping.
 #define CHECK_VALUEMAP_IMPL(RBName, Size, Offset)                              \
   do {                                                                         \
-    AArch64::PartialMappingIdx PartialMapBaseIdx =                             \
-        AArch64::PartialMappingIdx::PMI_##RBName##Size;                        \
-    (void) PartialMapBaseIdx;                                                  \
-    const ValueMapping &Map =                                                  \
-        AArch64::getValueMapping(AArch64::PMI_First##RBName, Size)[Offset];    \
-    (void) Map;                                                                \
+    unsigned PartialMapBaseIdx =                                               \
+        AArch64::PartialMappingIdx::PMI_##RBName##Size -                       \
+        AArch64::PartialMappingIdx::PMI_Min;                                   \
+    (void)PartialMapBaseIdx;                                                   \
+    const ValueMapping &Map = AArch64::getValueMapping(                        \
+        AArch64::PartialMappingIdx::PMI_First##RBName, Size)[Offset];          \
+    (void)Map;                                                                 \
     assert(Map.BreakDown == &AArch64::PartMappings[PartialMapBaseIdx] &&       \
            Map.NumBreakDowns == 1 && #RBName #Size                             \
            " " #Offset " is incorrectly initialized");                         \
@@ -172,10 +174,10 @@ AArch64RegisterBankInfo::AArch64RegisterBankInfo(const TargetRegisterInfo &TRI)
 
 #define CHECK_VALUEMAP_CROSSREGCPY(RBNameDst, RBNameSrc, Size)                 \
   do {                                                                         \
-    AArch64::PartialMappingIdx PartialMapDstIdx =                              \
-        AArch64::PartialMappingIdx::PMI_##RBNameDst##Size;                     \
-    AArch64::PartialMappingIdx PartialMapSrcIdx =                              \
-        AArch64::PartialMappingIdx::PMI_##RBNameSrc##Size;                     \
+    unsigned PartialMapDstIdx =                                                \
+        AArch64::PMI_##RBNameDst##Size - AArch64::PMI_Min;                     \
+    unsigned PartialMapSrcIdx =                                                \
+        AArch64::PMI_##RBNameSrc##Size - AArch64::PMI_Min;                     \
     (void) PartialMapDstIdx;                                                   \
     (void) PartialMapSrcIdx;                                                   \
     const ValueMapping *Map = AArch64::getCopyMapping(                         \