Set the default image base on arm64 and i386 to a superpage-aligned

address.

Reviewed by:	emaste, markj
Discussed with:	dim
Differential Revision:	https://reviews.freebsd.org/D16385

contrib/llvm/tools/lld/ELF/Arch/AArch64.cpp

@@ -66,6 +66,10 @@ AArch64::AArch64() {
   PltHeaderSize = 32;
   DefaultMaxPageSize = 65536;
 
+  // Align to the 2 MiB page size (known as a superpage or huge page).
+  // FreeBSD automatically promotes 2 MiB-aligned allocations.
+  DefaultImageBase = 0x200000;
+
   // It doesn't seem to be documented anywhere, but tls on aarch64 uses variant
   // 1 of the tls structures and the tcb size is 16.
   TcbSize = 16;

contrib/llvm/tools/lld/ELF/Arch/X86.cpp

@@ -61,6 +61,10 @@ X86::X86() {
   PltHeaderSize = 16;
   TlsGdRelaxSkip = 2;
   TrapInstr = 0xcccccccc; // 0xcc = INT3
+
+  // Align to the non-PAE large page size (known as a superpage or huge page).
+  // FreeBSD automatically promotes large, superpage-aligned allocations.
+  DefaultImageBase = 0x400000;
 }
 
 static bool hasBaseReg(uint8_t ModRM) { return (ModRM & 0xc7) != 0x5; }