From d2a5487fd79b0ce9cd303f84eae13ce12d4db4b7 Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Sun, 8 Oct 2023 22:10:02 +0200
Subject: [PATCH] ARM64: Use ADR and ADRP to form constants.

Thanks to Peter Cawley. #1100
---
 src/lj_emit_arm64.h   | 36 +++++++++++++++++++++++++++++-------
 src/lj_target_arm64.h |  2 ++
 2 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/src/lj_emit_arm64.h b/src/lj_emit_arm64.h
index 3c510492..51d0c351 100644
--- a/src/lj_emit_arm64.h
+++ b/src/lj_emit_arm64.h
@@ -193,6 +193,32 @@ static int emit_kdelta(ASMState *as, Reg rd, uint64_t k, int is64)
   return 0;  /* Failed. */
 }
 
+#define glofs(as, k) \
+  ((intptr_t)((uintptr_t)(k) - (uintptr_t)&J2GG(as->J)->g))
+#define mcpofs(as, k) \
+  ((intptr_t)((uintptr_t)(k) - (uintptr_t)(as->mcp - 1)))
+#define checkmcpofs(as, k) \
+  (A64F_S_OK(mcpofs(as, k)>>2, 19))
+
+/* Try to form a const as ADR or ADRP or ADRP + ADD. */
+static int emit_kadrp(ASMState *as, Reg rd, uint64_t k)
+{
+  A64Ins ai = A64I_ADR;
+  int64_t ofs = mcpofs(as, k);
+  if (!A64F_S_OK((uint64_t)ofs, 21)) {
+    uint64_t kpage = k & ~0xfffull;
+    MCode *adrp = as->mcp - 1 - (k != kpage);
+    ofs = (int64_t)(kpage - ((uint64_t)adrp & ~0xfffull)) >> 12;
+    if (!A64F_S_OK(ofs, 21))
+      return 0;  /* Failed. */
+    if (k != kpage)
+      emit_dn(as, (A64I_ADDx^A64I_K12)|A64F_U12(k - kpage), rd, rd);
+    ai = A64I_ADRP;
+  }
+  emit_d(as, ai|(((uint32_t)ofs&3)<<29)|A64F_S19(ofs>>2), rd);
+  return 1;
+}
+
 static void emit_loadk(ASMState *as, Reg rd, uint64_t u64)
 {
   int zeros = 0, ones = 0, neg, lshift = 0;
@@ -213,6 +239,9 @@ static void emit_loadk(ASMState *as, Reg rd, uint64_t u64)
     if (emit_kdelta(as, rd, u64, is64)) {
       return;
     }
+    if (emit_kadrp(as, rd, u64)) {  /* Either 1 or 2 ins. */
+      return;
+    }
   }
   if (neg) {
     u64 = ~u64;
@@ -240,13 +269,6 @@ static void emit_loadk(ASMState *as, Reg rd, uint64_t u64)
 /* Load a 64 bit constant into a GPR. */
 #define emit_loadu64(as, rd, i)	emit_loadk(as, rd, i)
 
-#define glofs(as, k) \
-  ((intptr_t)((uintptr_t)(k) - (uintptr_t)&J2GG(as->J)->g))
-#define mcpofs(as, k) \
-  ((intptr_t)((uintptr_t)(k) - (uintptr_t)(as->mcp - 1)))
-#define checkmcpofs(as, k) \
-  (A64F_S_OK(mcpofs(as, k)>>2, 19))
-
 static Reg ra_allock(ASMState *as, intptr_t k, RegSet allow);
 
 /* Get/set from constant pointer. */
diff --git a/src/lj_target_arm64.h b/src/lj_target_arm64.h
index 65a14307..c34f1e59 100644
--- a/src/lj_target_arm64.h
+++ b/src/lj_target_arm64.h
@@ -234,6 +234,8 @@ typedef enum A64Ins {
   A64I_MOVZx = 0xd2800000,
   A64I_MOVNw = 0x12800000,
   A64I_MOVNx = 0x92800000,
+  A64I_ADR = 0x10000000,
+  A64I_ADRP = 0x90000000,
 
   A64I_LDRB = 0x39400000,
   A64I_LDRH = 0x79400000,