AArch64: allow constant expressions for shifted reg literals

e.g., add w1, w2, w3, lsl #(2 - 1)

This sort of thing comes up in pre-processed assembly playing macro games.
Still validate that it's an assembly time constant. The early exit error check
was just a bit overzealous and disallowed a left paren.

rdar://18430542

llvm-svn: 218336

1 files changed, 7 insertions, 6 deletions

diff --git a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
index c4f5449d869..1c92c8c07b8 100644
--- a/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
+++ b/llvm/lib/Target/AArch64/AsmParser/AArch64AsmParser.cpp
@@ -2299,10 +2299,11 @@ AArch64AsmParser::tryParseOptionalShiftExtend(OperandVector &Operands) {
   if (Hash)
     Parser.Lex(); // Eat the '#'.
 
-  // Make sure we do actually have a number
-  if (!Parser.getTok().is(AsmToken::Integer)) {
-    Error(Parser.getTok().getLoc(),
-          "expected integer shift amount");
+  // Make sure we do actually have a number or a parenthesized expression.
+  SMLoc E = Parser.getTok().getLoc();
+  if (!Parser.getTok().is(AsmToken::Integer) &&
+      !Parser.getTok().is(AsmToken::LParen)) {
+    Error(E, "expected integer shift amount");
     return MatchOperand_ParseFail;
   }
 
@@ -2312,11 +2313,11 @@ AArch64AsmParser::tryParseOptionalShiftExtend(OperandVector &Operands) {
 
   const MCConstantExpr *MCE = dyn_cast<MCConstantExpr>(ImmVal);
   if (!MCE) {
-    TokError("expected #imm after shift specifier");
+    Error(E, "expected constant '#imm' after shift specifier");
     return MatchOperand_ParseFail;
   }
 
-  SMLoc E = SMLoc::getFromPointer(getLoc().getPointer() - 1);
+  E = SMLoc::getFromPointer(getLoc().getPointer() - 1);
   Operands.push_back(AArch64Operand::CreateShiftExtend(
       ShOp, MCE->getValue(), true, S, E, getContext()));
   return MatchOperand_Success;