From 0a8981186d4da342ef36179cf093e64674573c63 Mon Sep 17 00:00:00 2001
From: Robert Norton
Date: Tue, 2 Jul 2019 16:34:11 +0100
Subject: Add a fast path to speed up platform_read_ram: use fast_read_ram if
 read is 8 bytes or less to avoid cost of using GMP integers (including
 free/malloc).

---
 lib/rts.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/lib/rts.c b/lib/rts.c
index dfb2ba5a..57abbc3c 100644
--- a/lib/rts.c
+++ b/lib/rts.c
@@ -283,6 +283,13 @@ void platform_read_mem(lbits *data,
                        const sbits addr,
                        const mpz_t n)
 {
+  sbits sdata;
+  uint64_t len = mpz_get_ui(n); /* Sail type says always >0 */
+  if (len <= 8) {
+    /* fast path for small reads */
+    sdata = fast_read_ram(len, addr.bits);
+    RECREATE_OF(lbits, sbits)(data, sdata, true);
+  } else {
     mpz_t mpz_addr_size;
     mpz_init(mpz_addr_size);
     mpz_set_ui(mpz_addr_size, addr_size);
@@ -292,6 +299,7 @@ void platform_read_mem(lbits *data,
     read_ram(data, mpz_addr_size, n, (lbits){.len=0, .bits=NULL}, (lbits){.len=addr.len, .bits=&addr_bv});
     mpz_clear(mpz_addr_size);
     mpz_clear(addr_bv);
+  }
 }
 
 unit platform_write_mem_ea(const int write_kind,
-- 
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