Some ARM instructions encode 32-bit immediates as a 8-bit integer (0-255)
and a 4-bit rotation (0-30, even) in its least significant 12 bits. The
original fixup, FK_Data_4, patches the instruction by the value bit-to-bit,
regardless of the encoding. For example, assuming the label L1 and L2 are
0x0 and 0x104 respectively, the following instruction:
add r0, r0, #(L2 - L1) ; expects 0x104, i.e., 260
would be assembled to the following, which adds 1 to r0, instead of 260:
e2800104 add r0, r0, #4, 2 ; equivalently 1
The new fixup kind fixup_arm_mod_imm takes care of the encoding:
e2800f41 add r0, r0, #260
Patch by Ting-Yuan Huang!
llvm-svn: 265122
{"fixup_arm_movw_lo16", 0, 20, 0},
{"fixup_t2_movt_hi16", 0, 20, 0},
{"fixup_t2_movw_lo16", 0, 20, 0},
+ {"fixup_arm_mod_imm", 0, 12, 0},
};
const static MCFixupKindInfo InfosBE[ARM::NumTargetFixupKinds] = {
// This table *must* be in the order that the fixup_* kinds are defined in
{"fixup_arm_movw_lo16", 12, 20, 0},
{"fixup_t2_movt_hi16", 12, 20, 0},
{"fixup_t2_movw_lo16", 12, 20, 0},
+ {"fixup_arm_mod_imm", 20, 12, 0},
};
if (Kind < FirstTargetFixupKind)
return Value;
}
+ case ARM::fixup_arm_mod_imm:
+ Value = ARM_AM::getSOImmVal(Value);
+ if (Ctx && Value >> 12) {
+ Ctx->reportError(Fixup.getLoc(), "out of range immediate fixup value");
+ return 0;
+ }
+ return Value;
}
}
case FK_Data_2:
case ARM::fixup_arm_thumb_br:
case ARM::fixup_arm_thumb_cb:
+ case ARM::fixup_arm_mod_imm:
return 2;
case ARM::fixup_arm_pcrel_10_unscaled:
case ARM::fixup_arm_movw_lo16:
case ARM::fixup_t2_movt_hi16:
case ARM::fixup_t2_movw_lo16:
+ case ARM::fixup_arm_mod_imm:
// Instruction size is 4 bytes.
return 4;
}
fixup_t2_movt_hi16, // :upper16:
fixup_t2_movw_lo16, // :lower16:
+ // fixup_arm_mod_imm - Fixup for mod_imm
+ fixup_arm_mod_imm,
+
// Marker
LastTargetFixupKind,
NumTargetFixupKinds = LastTargetFixupKind - FirstTargetFixupKind
// Support for fixups (MCFixup)
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.
- // Due to requirements of relocatable records we have to use FK_Data_4.
- // See ARMELFObjectWriter::ExplicitRelSym and
- // ARMELFObjectWriter::GetRelocTypeInner for more details.
- MCFixupKind Kind = MCFixupKind(FK_Data_4);
+ // Fixups resolve to plain values that need to be encoded.
+ MCFixupKind Kind = MCFixupKind(ARM::fixup_arm_mod_imm);
Fixups.push_back(MCFixup::create(0, Expr, Kind, MI.getLoc()));
return 0;
}
@ CHECK: @ fixup A - offset: 0, value: fred, kind: fixup_arm_movw_lo16
@ CHECK-BE: movw r2, :lower16:fred @ encoding: [0xe3,0b0000AAAA,0x20'A',A]
@ CHECK-BE: @ fixup A - offset: 0, value: fred, kind: fixup_arm_movw_lo16
+
+ add r0, r0, #(L1 - L2)
+
+@ CHECK: add r0, r0, #L1-L2 @ encoding: [A,0b0000AAAA,0x80,0xe2]
+@ CHECK: @ fixup A - offset: 0, value: L1-L2, kind: fixup_arm_mod_imm
+@ CHECK-BE: add r0, r0, #L1-L2 @ encoding: [0xe2,0x80,0b0000AAAA,A]
+@ CHECK-BE: @ fixup A - offset: 0, value: L1-L2, kind: fixup_arm_mod_imm
--- /dev/null
+@ PR24346
+@ RUN: not llvm-mc -triple=arm-linux-gnueabi -filetype=obj < %s 2>&1 | FileCheck %s
+
+ .data
+ .align 8
+L2:
+ .word 0
+ .align 8
+ .byte 0
+L1:
+
+ .text
+@ CHECK: error: out of range immediate fixup value
+ add r0, r0, #(L1 - L2)
--- /dev/null
+@ PR24346
+@ RUN: llvm-mc < %s -triple=arm-linux-gnueabi -filetype=obj -o - \
+@ RUN: | llvm-objdump --disassemble -arch=arm - | FileCheck %s
+
+ .data
+ .align 8
+L2:
+ .word 0
+ .align 8
+ .word 0
+L1:
+
+ .text
+@ CHECK: add r0, r0, #260
+ add r0, r0, #(L1 - L2)