[ARM] Support fixup for Thumb2 modified immediate

    
This change adds a new fixup fixup_t2_so_imm for the t2_so_imm_asmoperand
"T2SOImm". The fixup permits code such as:
.L1:
 sub r3, r3, #.L2 - .L1
.L2:
to assemble in Thumb2 as well as in ARM state.
    
The operand predicate isT2SOImm() explicitly doesn't match expressions
containing :upper16: and :lower16: as expressions with these operators
must match the movt and movw instructions.
    
The test mov r0, foo2 in thumb2-diagnostics is moved to a new file as the
fixup delays the error message till after the assembler has quit due to
the other errors.
    
As the mov instruction shares the t2_so_imm_asmoperand mov instructions
with a non constant expression now match t2MOVi rather than t2MOVi16 so the
error message is slightly different.
    
Fixes PR28647

Differential Revision: https://reviews.llvm.org/D33492

llvm-svn: 304702

1 files changed, 11 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
index d9df2c6da7e..f1f35f40990 100644
--- a/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
+++ b/llvm/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
@@ -339,7 +339,17 @@ public:
   unsigned getT2SOImmOpValue(const MCInst &MI, unsigned Op,
                            SmallVectorImpl<MCFixup> &Fixups,
                            const MCSubtargetInfo &STI) const {
-    unsigned SoImm = MI.getOperand(Op).getImm();
+    const MCOperand &MO = MI.getOperand(Op);
+
+    // Support for fixups (MCFixup)
+    if (MO.isExpr()) {
+      const MCExpr *Expr = MO.getExpr();
+      // Fixups resolve to plain values that need to be encoded.
+      MCFixupKind Kind = MCFixupKind(ARM::fixup_t2_so_imm);
+      Fixups.push_back(MCFixup::create(0, Expr, Kind, MI.getLoc()));
+      return 0;
+    }
+    unsigned SoImm = MO.getImm();
     unsigned Encoded =  ARM_AM::getT2SOImmVal(SoImm);
     assert(Encoded != ~0U && "Not a Thumb2 so_imm value?");
     return Encoded;