[PATCH] D150005: [BOLT] Use opcode name in hashBlock

[Amir Ayupov via Phabricator via llvm-commits]

Amir created this revision.
Amir added a reviewer: bolt.
Herald added a reviewer: rafauler.
Herald added subscribers: treapster, ayermolo.
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Use MCInst opcode name instead of opcode value in hashing.

Opcode values are unstable wrt changes to target tablegen definitions,
and we notice that as output mismatches in NFC testing. This makes BOLT YAML
profile tied to a particular LLVM revision which is less portable than
offset-based fdata profile.

Switch to using opcode names which have 1:1 mapping with opcode values for any
given LLVM revision, and are stable wrt modifications to .td files (except of
course modifications to names themselves).


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D150005

Files:
  bolt/lib/Core/HashUtilities.cpp


Index: bolt/lib/Core/HashUtilities.cpp
===================================================================
--- bolt/lib/Core/HashUtilities.cpp
+++ bolt/lib/Core/HashUtilities.cpp
@@ -13,6 +13,7 @@
 #include "bolt/Core/HashUtilities.h"
 #include "bolt/Core/BinaryContext.h"
 #include "bolt/Core/BinaryFunction.h"
+#include "llvm/MC/MCInstPrinter.h"
 
 namespace llvm {
 namespace bolt {
@@ -116,13 +117,11 @@
     if (IsX86 && BC.MIB->isConditionalBranch(Inst))
       Opcode = BC.MIB->getShortBranchOpcode(Opcode);
 
-    if (Opcode == 0)
+    if (Opcode == 0) {
       HashString.push_back(0);
-
-    while (Opcode) {
-      uint8_t LSB = Opcode & 0xff;
-      HashString.push_back(LSB);
-      Opcode = Opcode >> 8;
+    } else {
+      StringRef OpcodeName = BC.InstPrinter->getOpcodeName(Opcode);
+      HashString.append(OpcodeName.str());
     }
 
     for (const MCOperand &Op : MCPlus::primeOperands(Inst))


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