[Memory] Call __clear_cache in InvalidateInstructionCache on LoongArch

[SixWeining]

As the comments of InvalidateInstructionCache: Before the JIT can run a block of code that has been emitted it must invalidate the instruction cache on some platforms. I think it applies to LoongArch as LoongArch has a weak memory-model. But I'm not able to write a test to demonstrate this issue. Perhaps self-modifing code should be wrote?

[llvmbot]

@llvm/pr-subscribers-llvm-support

Changes

As the comments of InvalidateInstructionCache: Before the JIT can run a block of code that has been emitted it must invalidate the instruction cache on some platforms. I think it applies to LoongArch as LoongArch has a weak memory-model. But I'm not able to write a test to demonstrate this issue. Perhaps self-modifing code should be wrote?

---

Full diff: https://github.com/llvm/llvm-project/pull/67285.diff

1 Files Affected:

• (modified) llvm/lib/Support/Unix/Memory.inc (+2-1)

diff --git a/llvm/lib/Support/Unix/Memory.inc b/llvm/lib/Support/Unix/Memory.inc
index 4c8f6b2ea7d3a09..69bd1164343da74 100644
--- a/llvm/lib/Support/Unix/Memory.inc
+++ b/llvm/lib/Support/Unix/Memory.inc
@@ -237,7 +237,8 @@ void Memory::InvalidateInstructionCache(const void *Addr, size_t Len) {
   for (intptr_t Line = StartLine; Line < EndLine; Line += LineSize)
     asm volatile("icbi 0, %0" : : "r"(Line));
   asm volatile("isync");
-#elif (defined(__arm__) || defined(__aarch64__) || defined(__mips__)) &&       \
+#elif (defined(__arm__) || defined(__aarch64__) || defined(__loongarch__) ||   \
+       defined(__mips__)) &&                                                   \
     defined(__GNUC__)
   // FIXME: Can we safely always call this for __GNUC__ everywhere?
   const char *Start = static_cast<const char *>(Addr);

[xen0n]

IIRC, __clear_cache is DBAR, and I think we need not only DBAR but also IBAR?

[SixWeining]

IIRC, __clear_cache is DBAR, and I think we need not only DBAR but also IBAR?

__clear_cache has different implementations:

• gcc: ibar 0
• libgcc: empty (I have reported this issue to gcc loongarch maintainers)
• compiler-rt: ibar 0

[xen0n]

IIRC, __clear_cache is DBAR, and I think we need not only DBAR but also IBAR?

__clear_cache has different implementations:

* gcc: `ibar 0`

* libgcc: empty (I have reported this issue to gcc loongarch maintainers)

* compiler-rt: `ibar 0`

Hmmm then I must have remembered it wrong (hence the "IIRC" prefix in my reply). No problem from my side then ;-)