Extend TableGen instruction selection matcher to improve handling

of complex instruction operands (e.g. address modes).

Currently, if a Pat pattern creates an instruction that has a complex
operand (i.e. one that consists of multiple sub-operands at the MI
level), this operand must match a ComplexPattern DAG pattern with the
correct number of output operands.

This commit extends TableGen to alternatively allow match a complex
operands against multiple separate operands at the DAG level.

This allows using Pat patterns to match pre-increment nodes like
pre_store (which must have separate operands at the DAG level) onto
an instruction pattern that uses a multi-operand memory operand,
like the following example on PowerPC (will be committed as a
follow-on patch):

  def STWU  : DForm_1<37, (outs ptr_rc:$ea_res), (ins GPRC:$rS, memri:$dst),
                    "stwu $rS, $dst", LdStStoreUpd, []>,
                    RegConstraint<"$dst.reg = $ea_res">, NoEncode<"$ea_res">;

  def : Pat<(pre_store GPRC:$rS, ptr_rc:$ptrreg, iaddroff:$ptroff),
            (STWU GPRC:$rS, iaddroff:$ptroff, ptr_rc:$ptrreg)>;

Here, the pair of "ptroff" and "ptrreg" operands is matched onto the
complex operand "dst" of class "memri" in the "STWU" instruction.

Approved by Jakob Stoklund Olesen.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177428 91177308-0d34-0410-b5e6-96231b3b80d8

docs/CodeGenerator.rst

@@ -1038,6 +1038,24 @@ for your target.  It has the following strengths:
   are used to manipulate the input immediate (in this case, take the high or low
   16-bits of the immediate).
 
+* When using the 'Pat' class to map a pattern to an instruction that has one
+  or more complex operands (like e.g. `X86 addressing mode`_), the pattern may
+  either specify the operand as a whole using a ``ComplexPattern``, or else it
+  may specify the components of the complex operand separately.  The latter is
+  done e.g. for pre-increment instructions by the PowerPC back end:
+
+  ::
+
+    def STWU  : DForm_1<37, (outs ptr_rc:$ea_res), (ins GPRC:$rS, memri:$dst),
+                    "stwu $rS, $dst", LdStStoreUpd, []>,
+                    RegConstraint<"$dst.reg = $ea_res">, NoEncode<"$ea_res">;
+
+    def : Pat<(pre_store GPRC:$rS, ptr_rc:$ptrreg, iaddroff:$ptroff),
+              (STWU GPRC:$rS, iaddroff:$ptroff, ptr_rc:$ptrreg)>;
+
+  Here, the pair of ``ptroff`` and ``ptrreg`` operands is matched onto the
+  complex operand ``dst`` of class ``memri`` in the ``STWU`` instruction.
+
 * While the system does automate a lot, it still allows you to write custom C++
   code to match special cases if there is something that is hard to
   express.

utils/TableGen/CodeGenDAGPatterns.cpp

@@ -1654,8 +1654,42 @@ bool TreePatternNode::ApplyTypeConstraints(TreePattern &TP, bool NotRegisters) {
 
       TreePatternNode *Child = getChild(ChildNo++);
       unsigned ChildResNo = 0;  // Instructions always use res #0 of their op.
+
+      // If the operand has sub-operands, they may be provided by distinct
+      // child patterns, so attempt to match each sub-operand separately.
+      if (OperandNode->isSubClassOf("Operand")) {
+        DagInit *MIOpInfo = OperandNode->getValueAsDag("MIOperandInfo");
+        if (unsigned NumArgs = MIOpInfo->getNumArgs()) {
+          // But don't do that if the whole operand is being provided by
+          // a single ComplexPattern.
+          const ComplexPattern *AM = Child->getComplexPatternInfo(CDP);
+          if (!AM || AM->getNumOperands() < NumArgs) {
+            // Match first sub-operand against the child we already have.
+            Record *SubRec = cast<DefInit>(MIOpInfo->getArg(0))->getDef();
+            MadeChange |=
+              Child->UpdateNodeTypeFromInst(ChildResNo, SubRec, TP);
+
+            // And the remaining sub-operands against subsequent children.
+            for (unsigned Arg = 1; Arg < NumArgs; ++Arg) {
+              if (ChildNo >= getNumChildren()) {
+                TP.error("Instruction '" + getOperator()->getName() +
+                         "' expects more operands than were provided.");
+                return false;
+              }
+              Child = getChild(ChildNo++);
+
+              SubRec = cast<DefInit>(MIOpInfo->getArg(Arg))->getDef();
+              MadeChange |=
+                Child->UpdateNodeTypeFromInst(ChildResNo, SubRec, TP);
+            }
+            continue;
+          }
+        }
+      }
+
+      // If we didn't match by pieces above, attempt to match the whole
+      // operand now.
       MadeChange |= Child->UpdateNodeTypeFromInst(ChildResNo, OperandNode, TP);
-      MadeChange |= Child->ApplyTypeConstraints(TP, NotRegisters);
     }
 
     if (ChildNo != getNumChildren()) {
@@ -1664,6 +1698,8 @@ bool TreePatternNode::ApplyTypeConstraints(TreePattern &TP, bool NotRegisters) {
       return false;
     }
 
+    for (unsigned i = 0, e = getNumChildren(); i != e; ++i)
+      MadeChange |= getChild(i)->ApplyTypeConstraints(TP, NotRegisters);
     return MadeChange;
   }
 

utils/TableGen/DAGISelMatcherGen.cpp

@@ -734,10 +734,22 @@ EmitResultInstructionAsOperand(const TreePatternNode *N,
       continue;
     }
 
-    const TreePatternNode *Child = N->getChild(ChildNo);
-
     // Otherwise this is a normal operand or a predicate operand without
     // 'execute always'; emit it.
+
+    // For operands with multiple sub-operands we may need to emit
+    // multiple child patterns to cover them all.  However, ComplexPattern
+    // children may themselves emit multiple MI operands.
+    unsigned NumSubOps = 1;
+    if (OperandNode->isSubClassOf("Operand")) {
+      DagInit *MIOpInfo = OperandNode->getValueAsDag("MIOperandInfo");
+      if (unsigned NumArgs = MIOpInfo->getNumArgs())
+        NumSubOps = NumArgs;
+    }
+
+    unsigned FinalNumOps = InstOps.size() + NumSubOps;
+    while (InstOps.size() < FinalNumOps) {
+      const TreePatternNode *Child = N->getChild(ChildNo);
       unsigned BeforeAddingNumOps = InstOps.size();
       EmitResultOperand(Child, InstOps);
       assert(InstOps.size() > BeforeAddingNumOps && "Didn't add any operands");
@@ -749,6 +761,7 @@ EmitResultInstructionAsOperand(const TreePatternNode *N,
 
       ++ChildNo;
     }
+  }
 
   // If this node has input glue or explicitly specified input physregs, we
   // need to add chained and glued copyfromreg nodes and materialize the glue