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[Hexagon] Fix encoding of packets with fixups followed by alignment #179168

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Merged
androm3da merged 2 commits into from
Feb 9, 2026
Merged

[Hexagon] Fix encoding of packets with fixups followed by alignment #179168

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6552458
[Hexagon] Fix encoding of packets with fixups followed by alignment
androm3da Feb 2, 2026
2fa80b1
Merge branch 'main' into bcain/fix_nvcj
androm3da Feb 9, 2026
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[Hexagon] Fix encoding of packets with fixups followed by alignment 
When a packet containing extended immediates and new-value compare-jump
instructions with fixups was followed by a .p2align directive, we
would incorrectly add nops to the packet. After reshuffling, the fixup
offsets would become invalid, causing corrupted encodings.

Fixes round-trip assembly for patterns like:

    {
      r18 = ##65536
      if (!cmp.gtu(r1,r18.new)) jump:t .L1
    }
    .p2align 4
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@androm3da
androm3da committed Feb 2, 2026
commit 6552458c13c3955c2bb6bc9adb7dc8c420633a25
7 changes: 7 additions & 0 deletions llvm/lib/Target/Hexagon/MCTargetDesc/HexagonAsmBackend.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -596,6 +596,13 @@ class HexagonAsmBackend : public MCAsmBackend {
auto &RF = *Frags[K];
MCInst Inst = RF.getInst();

// Don't add nops to packets that have fixups, as reshuffling can
// invalidate fixup offsets.
if (!RF.getVarFixups().empty()) {
Size = 0;
break;
}

const bool WouldTraverseLabel = llvm::any_of(
Asm->symbols(), [&RF, &Inst, Asm = Asm](MCSymbol const &sym) {
uint64_t Offset = 0;
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49 changes: 49 additions & 0 deletions llvm/test/MC/Hexagon/newvalue_jump_ext_imm.s
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@@ -0,0 +1,49 @@
# RUN: llvm-mc -triple=hexagon -filetype=obj %s | llvm-objdump -d - | FileCheck %s
# Test that packets with extended immediates and new-value compare-jumps
# followed by alignment directives are encoded and decoded correctly.

# CHECK-LABEL: <test1>:
# CHECK: immext(#0x10000)
# CHECK-NEXT: r18 = ##0x10000
# CHECK-NEXT: if (!cmp.gtu(r1,r18.new)) jump:t
test1:
.p2align 4
{
r18 = ##65536
if (!cmp.gtu(r1,r18.new)) jump:t .L1
}
.p2align 4
.L1:
nop

# CHECK-LABEL: <test2>:
# CHECK: immext(#0x20000)
# CHECK-NEXT: r19 = ##0x20000
# CHECK-NEXT: if (cmp.eq(r19.new,r2)) jump:nt
test2:
.p2align 4
{
r19 = ##131072
if (cmp.eq(r19.new,r2)) jump:nt .L2
}
.p2align 4
.L2:
nop

# CHECK-LABEL: <test3>:
# CHECK: allocframe(#0x10)
# CHECK-NEXT: memd(r29+#0x0) = r19:18
# CHECK: immext(#0x10000)
# CHECK-NEXT: r18 = ##0x10000
# CHECK-NEXT: if (!cmp.gtu(r1,r18.new)) jump:t
test3:
.p2align 4
allocframe(#16)
memd(r29+#0) = r19:18
{
r18 = ##65536
if (!cmp.gtu(r1,r18.new)) jump:t .L3
}
.p2align 4
.L3:
nop