release/19.x: [AVR][MC] Fix incorrect range of relative jumps (#109124)

[llvmbot]

Backport 8c3b94f

Requested by: @Patryk27

[llvmbot]

@jacquesguan What do you think about merging this PR to the release branch?

[llvmbot]

@llvm/pr-subscribers-mc

Author: None (llvmbot)

Changes

Backport 8c3b94f

Requested by: @Patryk27

---

Full diff: https://github.com/llvm/llvm-project/pull/113969.diff

2 Files Affected:

• (modified) llvm/lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp (+3-3)
• (modified) llvm/test/MC/AVR/inst-rjmp.s (+22-18)

diff --git a/llvm/lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp b/llvm/lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp
index 388d58a82214d1..c0bc1276967bf0 100644
--- a/llvm/lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp
+++ b/llvm/lib/Target/AVR/MCTargetDesc/AVRAsmBackend.cpp
@@ -88,15 +88,15 @@ static void adjustBranch(unsigned Size, const MCFixup &Fixup, uint64_t &Value,
 /// Adjusts the value of a relative branch target before fixup application.
 static void adjustRelativeBranch(unsigned Size, const MCFixup &Fixup,
                                  uint64_t &Value, MCContext *Ctx = nullptr) {
+  // Jumps are relative to the current instruction.
+  Value -= 2;
+
   // We have one extra bit of precision because the value is rightshifted by
   // one.
   signed_width(Size + 1, Value, std::string("branch target"), Fixup, Ctx);
 
   // Rightshifts the value by one.
   AVR::fixups::adjustBranchTarget(Value);
-
-  // Jumps are relative to the current instruction.
-  Value -= 1;
 }
 
 /// 22-bit absolute fixup.
diff --git a/llvm/test/MC/AVR/inst-rjmp.s b/llvm/test/MC/AVR/inst-rjmp.s
index cc843a58b55d2c..2d7aa401feacf0 100644
--- a/llvm/test/MC/AVR/inst-rjmp.s
+++ b/llvm/test/MC/AVR/inst-rjmp.s
@@ -19,25 +19,28 @@ end:
 x:
   rjmp x
   .short 0xc00f
+  rjmp .+4094
 
-; CHECK: rjmp (.Ltmp0+2)+2  ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: (.Ltmp0+2)+2, kind: fixup_13_pcrel
-; CHECK: rjmp (.Ltmp1-2)+2  ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: (.Ltmp1-2)+2, kind: fixup_13_pcrel
-; CHECK: rjmp foo           ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: foo, kind: fixup_13_pcrel
-; CHECK: rjmp (.Ltmp2+8)+2  ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: (.Ltmp2+8)+2, kind: fixup_13_pcrel
-; CHECK: rjmp end           ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: end, kind: fixup_13_pcrel
-; CHECK: rjmp (.Ltmp3+0)+2  ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: (.Ltmp3+0)+2, kind: fixup_13_pcrel
-; CHECK: rjmp (.Ltmp4-4)+2  ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: (.Ltmp4-4)+2, kind: fixup_13_pcrel
-; CHECK: rjmp (.Ltmp5-6)+2  ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: (.Ltmp5-6)+2, kind: fixup_13_pcrel
-; CHECK: rjmp x             ; encoding: [A,0b1100AAAA]
-; CHECK-NEXT:               ;   fixup A - offset: 0, value: x, kind: fixup_13_pcrel
+; CHECK: rjmp (.Ltmp0+2)+2    ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: (.Ltmp0+2)+2, kind: fixup_13_pcrel
+; CHECK: rjmp (.Ltmp1-2)+2    ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: (.Ltmp1-2)+2, kind: fixup_13_pcrel
+; CHECK: rjmp foo             ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: foo, kind: fixup_13_pcrel
+; CHECK: rjmp (.Ltmp2+8)+2    ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: (.Ltmp2+8)+2, kind: fixup_13_pcrel
+; CHECK: rjmp end             ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: end, kind: fixup_13_pcrel
+; CHECK: rjmp (.Ltmp3+0)+2    ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: (.Ltmp3+0)+2, kind: fixup_13_pcrel
+; CHECK: rjmp (.Ltmp4-4)+2    ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: (.Ltmp4-4)+2, kind: fixup_13_pcrel
+; CHECK: rjmp (.Ltmp5-6)+2    ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: (.Ltmp5-6)+2, kind: fixup_13_pcrel
+; CHECK: rjmp x               ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: x, kind: fixup_13_pcrel
+; CHECK: rjmp (.Ltmp6+4094)+2 ; encoding: [A,0b1100AAAA]
+; CHECK-NEXT:                 ;   fixup A - offset: 0, value: (.Ltmp6+4094)+2, kind: fixup_13_pcrel
 
 ; INST-LABEL: <foo>:
 ; INST-NEXT: 01 c0      rjmp  .+2
@@ -54,3 +57,4 @@ x:
 ; INST-LABEL: <x>:
 ; INST-NEXT: ff cf      rjmp  .-2
 ; INST-NEXT: 0f c0      rjmp  .+30
+; INST-NEXT: ff c7      rjmp  .+4094

[Patryk27]

A little context - I'd like to get it merged to 19.x, so that I can pull it to rustc - it fixes a minor codegen issue within the AVR backend, which causes some firmwares not to get compiled, crashing LLVM.

[github-actions]

@Patryk27 (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR.