Fix some unnoticed/unwanted behavior change from r222319.

The ARM assembler allows register alias redefinitions as long as it
targets the same register. r222319 broke that. In the AArch64 case
it would just produce a new warning, but in the ARM case it would
error out on previously accepted assembler.

llvm-svn: 228109

llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp

@@ -4132,7 +4132,7 @@ bool AArch64AsmParser::parseDirectiveReq(StringRef Name, SMLoc L) {
   Parser.Lex(); // Consume the EndOfStatement
 
   auto pair = std::make_pair(IsVector, RegNum);
-  if (!RegisterReqs.insert(std::make_pair(Name, pair)).second)
+  if (RegisterReqs.insert(std::make_pair(Name, pair)).first->second != pair)
     Warning(L, "ignoring redefinition of register alias '" + Name + "'");
 
   return true;

llvm/lib/Target/ARM/AsmParser/ARMAsmParser.cpp

@@ -9010,7 +9010,7 @@ bool ARMAsmParser::parseDirectiveReq(StringRef Name, SMLoc L) {
 
   Parser.Lex(); // Consume the EndOfStatement
 
-  if (!RegisterReqs.insert(std::make_pair(Name, Reg)).second) {
+  if (RegisterReqs.insert(std::make_pair(Name, Reg)).first->second != Reg) {
     Error(SRegLoc, "redefinition of '" + Name + "' does not match original.");
     return false;
   }

llvm/test/MC/AArch64/dot-req.s

@@ -1,7 +1,9 @@
-// RUN: llvm-mc -triple=aarch64-none-linux-gnu -show-encoding < %s | FileCheck %s
+// RUN: llvm-mc -triple=aarch64-none-linux-gnu -show-encoding < %s 2>&1 | FileCheck %s
 
 bar:
         fred .req x5
+// CHECK-NOT: ignoring redefinition of register alias 'fred'
+        fred .req x5
         mov fred, x11
         .unreq fred
         fred .req w6

llvm/test/MC/ARM/dot-req.s

@@ -1,6 +1,9 @@
 @ RUN: llvm-mc -triple=armv7-apple-darwin -show-encoding < %s | FileCheck %s
         .syntax unified
 bar:
+@ The line is duplicated on purpose, it is legal to redefine a req with
+@ the same value.
+fred .req r5
 fred .req r5
         mov r11, fred
 .unreq fred