Fix for pr18931: Crash using integrated assembler with immediate arithmetic

Fix description:
Expressions like 'cmp r0, #(l1 - l2) >> 3' could not be evaluated on asm parsing stage,
since it is impossible to resolve labels on this stage. In the end of stage we still have
expression (MCExpr).
Then, when we want to encode it, we expect it to be an immediate, but it still an expression.
Patch introduces a Fixup (MCFixup instance), that is processed after main encoding stage.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204899 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp b/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
index 3b2ca73aecd1d7677a9c8d68eaf46d524edf7329..6f8b699d4c5e55982f6520eb4582e8204abd8cf9 100644 (file)
--- a/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
+++ b/lib/Target/ARM/MCTargetDesc/ARMMCCodeEmitter.cpp
@@ -271,7 +271,23 @@ public:
   unsigned getSOImmOpValue(const MCInst &MI, unsigned Op,
                            SmallVectorImpl<MCFixup> &Fixups,
                            const MCSubtargetInfo &STI) const {
-    unsigned SoImm = MI.getOperand(Op).getImm();
+
+    const MCOperand &MO = MI.getOperand(Op);
+
+    // We expect MO to be an immediate or an expression,
+    // if it is an immediate - that's fine, just encode the value.
+    // Otherwise - create a Fixup.
+    if (MO.isExpr()) {
+      const MCExpr *Expr = MO.getExpr();
+      // In instruction code this value always encoded as lowest 12 bits,
+      // so we don't have to perform any specific adjustments and
+      // can use just 2-bytes fixup.
+      MCFixupKind Kind = MCFixupKind(FK_Data_2);
+      Fixups.push_back(MCFixup::Create(0, Expr, Kind, MI.getLoc()));
+      return 0;
+    }
+
+    unsigned SoImm = MO.getImm();
     int SoImmVal = ARM_AM::getSOImmVal(SoImm);
     assert(SoImmVal != -1 && "Not a valid so_imm value!");
 

diff --git a/test/MC/ARM/cmp-immediate-fixup.s b/test/MC/ARM/cmp-immediate-fixup.s
new file mode 100644 (file)
index 0000000..439e1d4
--- /dev/null
+++ b/test/MC/ARM/cmp-immediate-fixup.s
@@ -0,0 +1,9 @@
+// PR18931
+// RUN: llvm-mc < %s -triple=arm-linux-gnueabi -filetype=obj -o - \
+// RUN: | llvm-objdump --disassemble -arch=arm - | FileCheck %s
+
+    .text
+// CHECK: cmp r2, #1
+    cmp r2, #(l2 - l1 + 4) >> 2
+l1:
+l2: