X-Git-Url: https://www.bearssl.org/gitweb//home/git/?p=BearSSL;a=blobdiff_plain;f=src%2Fint%2Fi31_mulacc.c;h=7410e546727ccfba1e7dba201a0a075b2f711903;hp=024d095665a6b5c6f0e46eb4479386cc8dd03e18;hb=001d094d140488def90cb3876d5c03f4d79b3e27;hpb=08eb07825be067729dff343de2d9a0c13252b415;ds=sidebyside

diff --git a/src/int/i31_mulacc.c b/src/int/i31_mulacc.c
index 024d095..7410e54 100644
--- a/src/int/i31_mulacc.c
+++ b/src/int/i31_mulacc.c
@@ -45,7 +45,20 @@ br_i31_mulacc(uint32_t *d, const uint32_t *a, const uint32_t *b)
 	for (u = 0; u < blen; u ++) {
 		uint32_t f;
 		size_t v;
+
+		/*
+		 * Carry always fits on 31 bits; we want to keep it in a
+		 * 32-bit register on 32-bit architectures (on a 64-bit
+		 * architecture, cast down from 64 to 32 bits means
+		 * clearing the high bits, which is not free; on a 32-bit
+		 * architecture, the same operation really means ignoring
+		 * the top register, which has negative or zero cost).
+		 */
+#if BR_64
 		uint64_t cc;
+#else
+		uint32_t cc;
+#endif
 
 		f = b[1 + u];
 		cc = 0;