[dev.cc] cmd/asm: fix macro definition bug in the lexer

Because text/scanner hides the spaces, the lexer treated
	#define A(x)
and
	#define A (x)
the same, but they are not: the first is an argument with macros, the
second is a simple one-word macro whose definition contains parentheses.
Fix this by noticing the relative column number as we move from A to (.
Hacky but simple.

Also add a helper to recognize the peculiar ARM shifted register operators.

Change-Id: I2cad22f5f1e11d8dad40ad13955793d178afb3ae
Reviewed-on: https://go-review.googlesource.com/4872
Reviewed-by: Russ Cox <rsc@golang.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/cmd/asm/internal/lex/stack.go b/src/cmd/asm/internal/lex/stack.go
index 9766af51de..72d7f8a165 100644
--- a/src/cmd/asm/internal/lex/stack.go
+++ b/src/cmd/asm/internal/lex/stack.go
@@ -41,6 +41,10 @@ func (s *Stack) Line() int {
 	return s.tr[len(s.tr)-1].Line()
 }
 
+func (s *Stack) Col() int {
+	return s.tr[len(s.tr)-1].Col()
+}
+
 func (s *Stack) SetPos(line int, file string) {
 	s.tr[len(s.tr)-1].SetPos(line, file)
 }