[llvm] [hwasan] Optimize outlined memaccess for fixed shadow on Aarch64 (PR #88544)

[Vitaly Buka via llvm-commits]

================
@@ -625,14 +638,32 @@ void AArch64AsmPrinter::emitHwasanMemaccessSymbols(Module &M) {
                                      .addImm(4)
                                      .addImm(55),
                                  *STI);
-    OutStreamer->emitInstruction(
-        MCInstBuilder(AArch64::LDRBBroX)
-            .addReg(AArch64::W16)
-            .addReg(IsShort ? AArch64::X20 : AArch64::X9)
-            .addReg(AArch64::X16)
-            .addImm(0)
-            .addImm(0),
-        *STI);
+
+    if (HwasanFixedShadowBase != (unsigned long long)-1) {
+      assert(IsShort);
----------------
vitalybuka wrote:

At this stage better to make it simple without assumptions about android.
We have intrinsic then just lower it, it's up to HWASAN pass to generate code right.

https://github.com/llvm/llvm-project/pull/88544