[ARM][Asm] Debug trace for the processInstruction loop

In the Arm assembly parser, we first match an instruction, then call
processInstruction to possibly change it to a different encoding, to
match rules in the architecture manual which can't be expressed by the
table-generated matcher.

This adds debug printing so that this process is visible when using the
-debug option.

To support this, I've added a new overload of MCInst::dump_pretty which
takes the opcode name as a StringRef, since we don't have an InstPrinter
instance in the assembly parser. Instead, we can get the same
information directly from the MCInstrInfo.

Differential revision: https://reviews.llvm.org/D54852

llvm-svn: 348113

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index a2883191178..203da11ed32 100644
--- a/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -9310,6 +9310,10 @@ bool ARMAsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
 
   switch (MatchResult) {
   case Match_Success:
+    LLVM_DEBUG(dbgs() << "Parsed as: ";
+               Inst.dump_pretty(dbgs(), MII.getName(Inst.getOpcode()));
+               dbgs() << "\n");
+
     // Context sensitive operand constraints aren't handled by the matcher,
     // so check them here.
     if (validateInstruction(Inst, Operands)) {
@@ -9327,7 +9331,9 @@ bool ARMAsmParser::MatchAndEmitInstruction(SMLoc IDLoc, unsigned &Opcode,
       // individual transformations can chain off each other. E.g.,
       // tPOP(r8)->t2LDMIA_UPD(sp,r8)->t2STR_POST(sp,r8)
       while (processInstruction(Inst, Operands, Out))
-        ;
+        LLVM_DEBUG(dbgs() << "Changed to: ";
+                   Inst.dump_pretty(dbgs(), MII.getName(Inst.getOpcode()));
+                   dbgs() << "\n");
 
       // Only after the instruction is fully processed, we can validate it
       if (wasInITBlock && hasV8Ops() && isThumb() &&