[lld][AVR] Fix range of R_AVR_7_PCREL

R_AVR_7_PCREL has 7 bits available, but because it works in instruction
words the actual range is 256 bytes (-128..126 bytes).

This fixes a bug introduced in
#67636 that caused code
generated by the compiler to be rejected by the linker.

There is still a bug in the compiler: it can use one more bit for
R_AVR_7_PCREL than it currently does. But that should be fixed
separately.

Author: aykevl

lld/ELF/Arch/AVR.cpp

@@ -231,7 +231,7 @@ void AVR::relocate(uint8_t *loc, const Relocation &rel, uint64_t val) const {
 
   // Since every jump destination is word aligned we gain an extra bit
   case R_AVR_7_PCREL: {
-    checkInt(loc, val - 2, 7, rel);
+    checkInt(loc, val - 2, 8, rel);
     checkAlignment(loc, val, 2, rel);
     const uint16_t target = (val - 2) >> 1;
     write16le(loc, (read16le(loc) & 0xfc07) | ((target & 0x7f) << 3));

lld/test/ELF/avr-reloc-error.s

@@ -3,7 +3,7 @@
 # RUN: rm -rf %t && split-file %s %t && cd %t
 
 # RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328 avr-pcrel-7.s -o avr-pcrel-7.o
-# RUN: not ld.lld avr-pcrel-7.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x1040 --defsym=callee1=0x1044 --defsym=callee2=0x100f 2>&1 | \
+# RUN: not ld.lld avr-pcrel-7.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x1040 --defsym=callee1=0x1084 --defsym=callee2=0x100f 2>&1 | \
 # RUN:     FileCheck %s --check-prefix=PCREL7
 # RUN: llvm-mc -filetype=obj -triple=avr -mcpu=atmega328 avr-pcrel-13.s -o avr-pcrel-13.o
 # RUN: not ld.lld avr-pcrel-13.o -o /dev/null -Ttext=0x1000 --defsym=callee0=0x2000 --defsym=callee1=0x2004 --defsym=callee2=0x100f 2>&1 | \
@@ -20,7 +20,7 @@
 __start:
 
 # PCREL7-NOT: callee0
-# PCREL7:     error: {{.*}} relocation R_AVR_7_PCREL out of range: {{.*}} is not in [-64, 63]; references 'callee1'
+# PCREL7:     error: {{.*}} relocation R_AVR_7_PCREL out of range: {{.*}} is not in [-128, 127]; references 'callee1'
 # PCREL7:     error: {{.*}} improper alignment for relocation R_AVR_7_PCREL: {{.*}} is not aligned to 2 bytes
 brne callee0
 breq callee1

lld/test/ELF/avr-reloc.s

@@ -82,13 +82,17 @@ sbic  b, 1    ; R_AVR_PORT5
 ; CHECK-NEXT:  rjmp .-36
 ; CHECK-NEXT:  breq .+26
 ; CHECK-NEXT:  breq .-40
+; CHECK-NEXT:  breq .-128
+; CHECK-NEXT:  breq .+126
 ; HEX-LABEL:   section .PCREL:
 ; HEX-NEXT:    0fc0eecf 69f061f3
 foo:
 rjmp foo + 32  ; R_AVR_13_PCREL
 rjmp foo - 32  ; R_AVR_13_PCREL
 breq foo + 32  ; R_AVR_7_PCREL
 breq foo - 32  ; R_AVR_7_PCREL
+breq 1f - 128   $ 1:  ; R_AVR_7_PCREL
+breq 1f + 126   $ 1:  ; R_AVR_7_PCREL
 
 .section .LDSSTS,"ax",@progbits
 ; CHECK-LABEL: section .LDSSTS: