File 2122-Introduce-erts_copy_bits_restricted.patch of Package erlang

From 162529c5a0685e24072a22d8302b1b76c704c7b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Gustavsson?= <bjorn@erlang.org>
Date: Tue, 17 May 2022 10:19:33 +0200
Subject: [PATCH 2/3] Introduce erts_copy_bits_restricted()

Useful for the JIT because it has fewer arguments and thus can be
called using fewer instructions.
---
 erts/emulator/beam/erl_bits.c | 21 ++++++++++++++++++++-
 erts/emulator/beam/erl_bits.h |  3 ++-
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/erts/emulator/beam/erl_bits.c b/erts/emulator/beam/erl_bits.c
index 108842a54f..da24aae054 100644
--- a/erts/emulator/beam/erl_bits.c
+++ b/erts/emulator/beam/erl_bits.c
@@ -884,7 +884,7 @@ erts_new_bs_put_integer(ERL_BITS_PROTO_3(Eterm arg, Uint num_bits, unsigned flag
 	if (fmt_int(iptr, NBYTES(num_bits), arg, num_bits, flags) < 0) {
 	    return 0;
 	}
-	erts_copy_bits(iptr, 0, 1, erts_current_bin, bin_offset, 1, num_bits);
+	erts_copy_bits_restricted(iptr, erts_current_bin, bin_offset, num_bits);
     }
     erts_bin_offset = bin_offset + num_bits;
     return 1;
@@ -2150,6 +2150,25 @@ erts_cmp_bits(byte* a_ptr, size_t a_offs, byte* b_ptr, size_t b_offs, size_t siz
     return 0;
 }
 
+/*
+ * Restricted version of copy_bits() for copying from a buffer into
+ * a binary. Direction is always forward and the source offset is always
+ * zero.
+ */
+void
+erts_copy_bits_restricted(byte* src,	/* Base pointer to source. */
+                          byte* dst,	/* Base pointer to destination. */
+                          size_t doffs, /* Bit offset for destination relative to dst. */
+                          size_t n)     /* Number of bits to copy. */
+{
+    if (doffs == 0) {
+        abort();
+    }
+    ASSERT(n != 0);
+    ASSERT(doffs != 0);
+    erts_copy_bits(src, 0, 1, dst, doffs, 1, n);
+}
+
 /*
  * The basic bit copy operation. Copies n bits from the source buffer to
  * the destination buffer. Depending on the directions, it can reverse the
diff --git a/erts/emulator/beam/erl_bits.h b/erts/emulator/beam/erl_bits.h
index 34af1051d4..136d3357ce 100644
--- a/erts/emulator/beam/erl_bits.h
+++ b/erts/emulator/beam/erl_bits.h
@@ -188,7 +188,8 @@ Eterm erts_bs_init_writable(Process* p, Eterm sz);
  * Common utilities.
  */
 void erts_copy_bits(byte* src, size_t soffs, int sdir,
-		    byte* dst, size_t doffs,int ddir, size_t n);        
+		    byte* dst, size_t doffs,int ddir, size_t n);
+void erts_copy_bits_restricted(byte* src, byte* dst, size_t doffs, size_t n);
 int erts_cmp_bits(byte* a_ptr, size_t a_offs, byte* b_ptr, size_t b_offs, size_t size); 
 
 
-- 
2.35.3