[globalisel] Change LLT constructor string into an LLT-based object that knows how to generate it.

Summary:
This will allow future patches to inspect the details of the LLT. The implementation is now split between
the Support and CodeGen libraries to allow TableGen to use this class without introducing layering concerns.

Thanks to Ahmed Bougacha for finding a reasonable way to avoid the layering issue and providing the version of this patch without that problem.

Reviewers: t.p.northover, qcolombet, rovka, aditya_nandakumar, ab, javed.absar

Subscribers: arsenm, nhaehnle, mgorny, dberris, llvm-commits, kristof.beyls

Differential Revision: https://reviews.llvm.org/D30046

llvm-svn: 297177

1 files changed, 35 insertions, 16 deletions

diff --git a/llvm/utils/TableGen/GlobalISelEmitter.cpp b/llvm/utils/TableGen/GlobalISelEmitter.cpp
index 238a50a94c6..0da1b86021a 100644
--- a/llvm/utils/TableGen/GlobalISelEmitter.cpp
+++ b/llvm/utils/TableGen/GlobalISelEmitter.cpp
@@ -33,6 +33,7 @@
 #include "CodeGenDAGPatterns.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/LowLevelType.h"
 #include "llvm/CodeGen/MachineValueType.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Error.h"
@@ -58,22 +59,38 @@ static cl::opt<bool> WarnOnSkippedPatterns(
 
 //===- Helper functions ---------------------------------------------------===//
 
+/// This class stands in for LLT wherever we want to tablegen-erate an
+/// equivalent at compiler run-time.
+class LLTCodeGen {
+private:
+  LLT Ty;
+
+public:
+  LLTCodeGen(const LLT &Ty) : Ty(Ty) {}
+
+  void emitCxxConstructorCall(raw_ostream &OS) const {
+    if (Ty.isScalar()) {
+      OS << "LLT::scalar(" << Ty.getSizeInBits() << ")";
+      return;
+    }
+    if (Ty.isVector()) {
+      OS << "LLT::vector(" << Ty.getNumElements() << ", " << Ty.getSizeInBits()
+         << ")";
+      return;
+    }
+    llvm_unreachable("Unhandled LLT");
+  }
+};
+
 /// Convert an MVT to an equivalent LLT if possible, or the invalid LLT() for
 /// MVTs that don't map cleanly to an LLT (e.g., iPTR, *any, ...).
-static Optional<std::string> MVTToLLT(MVT::SimpleValueType SVT) {
-  std::string TyStr;
-  raw_string_ostream OS(TyStr);
+static Optional<LLTCodeGen> MVTToLLT(MVT::SimpleValueType SVT) {
   MVT VT(SVT);
-  if (VT.isVector() && VT.getVectorNumElements() != 1) {
-    OS << "LLT::vector(" << VT.getVectorNumElements() << ", "
-       << VT.getScalarSizeInBits() << ")";
-  } else if (VT.isInteger() || VT.isFloatingPoint()) {
-    OS << "LLT::scalar(" << VT.getSizeInBits() << ")";
-  } else {
-    return None;
-  }
-  OS.flush();
-  return TyStr;
+  if (VT.isVector() && VT.getVectorNumElements() != 1)
+    return LLTCodeGen(LLT::vector(VT.getVectorNumElements(), VT.getScalarSizeInBits()));
+  if (VT.isInteger() || VT.isFloatingPoint())
+    return LLTCodeGen(LLT::scalar(VT.getSizeInBits()));
+  return None;
 }
 
 static bool isTrivialOperatorNode(const TreePatternNode *N) {
@@ -167,10 +184,10 @@ public:
 /// Generates code to check that an operand is a particular LLT.
 class LLTOperandMatcher : public OperandPredicateMatcher {
 protected:
-  std::string Ty;
+  LLTCodeGen Ty;
 
 public:
-  LLTOperandMatcher(std::string Ty)
+  LLTOperandMatcher(const LLTCodeGen &Ty)
       : OperandPredicateMatcher(OPM_LLT), Ty(Ty) {}
 
   static bool classof(const OperandPredicateMatcher *P) {
@@ -179,7 +196,9 @@ public:
 
   void emitCxxPredicateExpr(raw_ostream &OS,
                             StringRef OperandExpr) const override {
-    OS << "MRI.getType(" << OperandExpr << ".getReg()) == (" << Ty << ")";
+    OS << "MRI.getType(" << OperandExpr << ".getReg()) == (";
+    Ty.emitCxxConstructorCall(OS);
+    OS << ")";
   }
 };