[mips] Add error message when trying to use $at in '.set noat' mode.

Summary:
Patch by David Chisnall
His work was sponsored by: DARPA, AFRL

Differential Revision: http://llvm-reviews.chandlerc.com/D3158

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204621 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
index 8c0c181feca692646aeed23b839584aa075497e0..f54a62b666cf754c8235c504c0f921cae190fe0b 100644 (file)
--- a/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ b/lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -1174,7 +1174,12 @@ bool MipsAssemblerOptions::setATReg(unsigned Reg) {
   return true;
 }
 
-int MipsAsmParser::getATReg() { return Options.getATRegNum(); }
+int MipsAsmParser::getATReg() {
+  int AT = Options.getATRegNum();
+  if (AT == 0)
+    TokError("Pseudo instruction requires $at, which is not available");
+  return AT;
+}
 
 unsigned MipsAsmParser::getReg(int RC, int RegNo) {
   return *(getContext().getRegisterInfo()->getRegClass(RC).begin() + RegNo);

diff --git a/test/MC/Mips/mips-noat.s b/test/MC/Mips/mips-noat.s
new file mode 100644 (file)
index 0000000..152a1ee
--- /dev/null
+++ b/test/MC/Mips/mips-noat.s
@@ -0,0 +1,27 @@
+# RUN: not llvm-mc %s -triple=mips-unknown-linux 2>%t0 | FileCheck %s
+# RUN: FileCheck -check-prefix=ERROR %s < %t0
+
+# We start with $at enabled
+# CHECK-LABEL: test1:
+# CHECK:  lui   $1, 1
+# CHECK:  addu  $1, $1, $2
+# CHECK:  lw    $2, 0($1)
+test1:
+        lw      $2, 65536($2)
+
+# Check that using $at when .set noat is in effect is an error.
+# FIXME: It would be better if the error pointed at the mnemonic instead of the newline
+# ERROR: mips-noat.s:[[@LINE+5]]:1: error: Pseudo instruction requires $at, which is not available
+# ERROR-NOT: error
+test2:
+        .set noat
+        lw      $2, 65536($2)
+
+# Can we switch it back on successfully?
+# CHECK-LABEL: test3:
+# CHECK:  lui   $1, 1
+# CHECK:  addu  $1, $1, $2
+# CHECK:  lw    $2, 0($1)
+test3:
+        .set at
+        lw      $2, 65536($2)