Add support for binary encoding of ARM 'adr' instructions referencing constant

pool entries (LEApcrel pseudo). Ongoing saga of rdar://8542291.

llvm-svn: 120635

1 files changed, 18 insertions, 3 deletions

diff --git a/llvm/lib/Target/ARM/ARMAsmBackend.cpp b/llvm/lib/Target/ARM/ARMAsmBackend.cpp
index c07a8160684..eb03a24b026 100644
--- a/llvm/lib/Target/ARM/ARMAsmBackend.cpp
+++ b/llvm/lib/Target/ARM/ARMAsmBackend.cpp
@@ -7,8 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/Target/TargetAsmBackend.h"
 #include "ARM.h"
+#include "ARMAddressingModes.h"
 #include "ARMFixupKinds.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCAssembler.h"
@@ -21,6 +21,7 @@
 #include "llvm/Support/ELF.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetAsmBackend.h"
 #include "llvm/Target/TargetRegistry.h"
 using namespace llvm;
 
@@ -67,7 +68,7 @@ static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
   case ARM::fixup_arm_movt_hi16:
   case ARM::fixup_arm_movw_lo16:
     return Value;
-  case ARM::fixup_arm_pcrel_12: {
+  case ARM::fixup_arm_ldst_pcrel_12: {
     bool isAdd = true;
     // ARM PC-relative values are offset by 8.
     Value -= 8;
@@ -79,6 +80,19 @@ static unsigned adjustFixupValue(unsigned Kind, uint64_t Value) {
     Value |= isAdd << 23;
     return Value;
   }
+  case ARM::fixup_arm_adr_pcrel_12: {
+    // ARM PC-relative values are offset by 8.
+    Value -= 8;
+    unsigned opc = 4; // bits {24-21}. Default to add: 0b0100
+    if ((int64_t)Value < 0) {
+      Value = -Value;
+      opc = 2; // 0b0010
+    }
+    assert(ARM_AM::getSOImmVal(Value) != -1 &&
+           "Out of range pc-relative fixup value!");
+    // Encode the immediate and shift the opcode into place.
+    return ARM_AM::getSOImmVal(Value) | (opc << 21);
+  }
   case ARM::fixup_arm_branch:
     // These values don't encode the low two bits since they're always zero.
     // Offset by 8 just as above.
@@ -200,8 +214,9 @@ static unsigned getFixupKindNumBytes(unsigned Kind) {
   switch (Kind) {
   default: llvm_unreachable("Unknown fixup kind!");
   case FK_Data_4: return 4;
-  case ARM::fixup_arm_pcrel_12: return 3;
+  case ARM::fixup_arm_ldst_pcrel_12: return 3;
   case ARM::fixup_arm_pcrel_10: return 3;
+  case ARM::fixup_arm_adr_pcrel_12: return 3;
   case ARM::fixup_arm_branch: return 3;
   }
 }