[PATCH] D139285: [LoongArch] Allow writing unaligned nop sequences

[wanglei via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rG1d3baf21b673: [LoongArch] Allow writing unaligned nop sequences (authored by wangleiat).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D139285/new/

https://reviews.llvm.org/D139285

Files:
  llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
  llvm/test/MC/LoongArch/Misc/unaligned-nops.s


Index: llvm/test/MC/LoongArch/Misc/unaligned-nops.s
===================================================================
--- llvm/test/MC/LoongArch/Misc/unaligned-nops.s
+++ llvm/test/MC/LoongArch/Misc/unaligned-nops.s
@@ -1,5 +1,8 @@
-# RUN: not --crash llvm-mc --filetype=obj --triple=loongarch64 %s -o %t
+# RUN: llvm-mc --triple=loongarch64 --filetype=obj %s -o %t
+# RUN: llvm-objdump -d %t | FileCheck %s
+
+# CHECK:      01 00 00 00   <unknown>
+# CHECK-NEXT: 00 00 40 03   nop
 .byte 1
-# CHECK: LLVM ERROR: unable to write nop sequence of 3 bytes
-.p2align 2
+.p2align 3
 foo:
Index: llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
===================================================================
--- llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
+++ llvm/lib/Target/LoongArch/MCTargetDesc/LoongArchAsmBackend.cpp
@@ -179,13 +179,14 @@
 
 bool LoongArchAsmBackend::writeNopData(raw_ostream &OS, uint64_t Count,
                                        const MCSubtargetInfo *STI) const {
-  // Check for byte count not multiple of instruction word size
-  if (Count % 4 != 0)
-    return false;
+  // We mostly follow binutils' convention here: align to 4-byte boundary with a
+  // 0-fill padding.
+  OS.write_zeros(Count % 4);
 
-  // The nop on LoongArch is andi r0, r0, 0.
+  // The remainder is now padded with 4-byte nops.
+  // nop: andi r0, r0, 0
   for (; Count >= 4; Count -= 4)
-    support::endian::write<uint32_t>(OS, 0x03400000, support::little);
+    OS.write("\0\0\x40\x03", 4);
 
   return true;
 }


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