[TableGen] Support encoding per-HwMode

Much like ValueTypeByHwMode/RegInfoByHwMode, this patch allows targets
to modify an instruction's encoding based on HwMode. When the
EncodingInfos field is non-empty the Inst and Size fields of the Instruction
are ignored and taken from EncodingInfos instead.

As part of this promote getHwMode() from TargetSubtargetInfo to MCSubtargetInfo.

This is NFC for all existing targets - new code is generated only if targets
use EncodingByHwMode.

llvm-svn: 372320

1 files changed, 56 insertions, 9 deletions

diff --git a/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp b/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
index 01f4115aa1d..ac69b431607 100644
--- a/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
+++ b/llvm/utils/TableGen/FixedLenDecoderEmitter.cpp
@@ -13,6 +13,7 @@
 
 #include "CodeGenInstruction.h"
 #include "CodeGenTarget.h"
+#include "InfoByHwMode.h"
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/CachedHashString.h"
@@ -97,9 +98,11 @@ struct DecoderTableInfo {
 struct EncodingAndInst {
   const Record *EncodingDef;
   const CodeGenInstruction *Inst;
+  StringRef HwModeName;
 
-  EncodingAndInst(const Record *EncodingDef, const CodeGenInstruction *Inst)
-      : EncodingDef(EncodingDef), Inst(Inst) {}
+  EncodingAndInst(const Record *EncodingDef, const CodeGenInstruction *Inst,
+                  StringRef HwModeName = "")
+      : EncodingDef(EncodingDef), Inst(Inst), HwModeName(HwModeName) {}
 };
 
 struct EncodingIDAndOpcode {
@@ -2382,12 +2385,50 @@ void FixedLenDecoderEmitter::run(raw_ostream &o) {
   Target.reverseBitsForLittleEndianEncoding();
 
   // Parameterize the decoders based on namespace and instruction width.
+  std::set<StringRef> HwModeNames;
   const auto &NumberedInstructions = Target.getInstructionsByEnumValue();
   NumberedEncodings.reserve(NumberedInstructions.size());
   DenseMap<Record *, unsigned> IndexOfInstruction;
+  // First, collect all HwModes referenced by the target.
   for (const auto &NumberedInstruction : NumberedInstructions) {
     IndexOfInstruction[NumberedInstruction->TheDef] = NumberedEncodings.size();
-    NumberedEncodings.emplace_back(NumberedInstruction->TheDef, NumberedInstruction);
+
+    if (const RecordVal *RV =
+            NumberedInstruction->TheDef->getValue("EncodingInfos")) {
+      if (auto *DI = dyn_cast_or_null<DefInit>(RV->getValue())) {
+        const CodeGenHwModes &HWM = Target.getHwModes();
+        EncodingInfoByHwMode EBM(DI->getDef(), HWM);
+        for (auto &KV : EBM.Map)
+          HwModeNames.insert(HWM.getMode(KV.first).Name);
+      }
+    }
+  }
+
+  // If HwModeNames is empty, add the empty string so we always have one HwMode.
+  if (HwModeNames.empty())
+    HwModeNames.insert("");
+
+  for (const auto &NumberedInstruction : NumberedInstructions) {
+    IndexOfInstruction[NumberedInstruction->TheDef] = NumberedEncodings.size();
+
+    if (const RecordVal *RV =
+            NumberedInstruction->TheDef->getValue("EncodingInfos")) {
+      if (DefInit *DI = dyn_cast_or_null<DefInit>(RV->getValue())) {
+        const CodeGenHwModes &HWM = Target.getHwModes();
+        EncodingInfoByHwMode EBM(DI->getDef(), HWM);
+        for (auto &KV : EBM.Map) {
+          NumberedEncodings.emplace_back(KV.second, NumberedInstruction,
+                                         HWM.getMode(KV.first).Name);
+          HwModeNames.insert(HWM.getMode(KV.first).Name);
+        }
+        continue;
+      }
+    }
+    // This instruction is encoded the same on all HwModes. Emit it for all
+    // HwModes.
+    for (StringRef HwModeName : HwModeNames)
+      NumberedEncodings.emplace_back(NumberedInstruction->TheDef,
+                                     NumberedInstruction, HwModeName);
   }
   for (const auto &NumberedAlias : RK.getAllDerivedDefinitions("AdditionalEncoding"))
     NumberedEncodings.emplace_back(
@@ -2415,13 +2456,19 @@ void FixedLenDecoderEmitter::run(raw_ostream &o) {
       NumInstructions++;
     NumEncodings++;
 
-    StringRef DecoderNamespace = EncodingDef->getValueAsString("DecoderNamespace");
+    if (!Size)
+      continue;
 
-    if (Size) {
-      if (populateInstruction(Target, *EncodingDef, *Inst, i, Operands)) {
-        OpcMap[std::make_pair(DecoderNamespace, Size)].emplace_back(i, IndexOfInstruction.find(Def)->second);
-      } else
-        NumEncodingsOmitted++;
+    if (populateInstruction(Target, *EncodingDef, *Inst, i, Operands)) {
+      std::string DecoderNamespace =
+          EncodingDef->getValueAsString("DecoderNamespace");
+      if (!NumberedEncodings[i].HwModeName.empty())
+        DecoderNamespace +=
+            std::string("_") + NumberedEncodings[i].HwModeName.str();
+      OpcMap[std::make_pair(DecoderNamespace, Size)].emplace_back(
+          i, IndexOfInstruction.find(Def)->second);
+    } else {
+      NumEncodingsOmitted++;
     }
   }