Allow divsi3 to take advantage of a hardware unsigned divide when it is available, by replacing an explicit call to udivsi3 with the divide operator. Patch by Sébastien Bourdeauducq.

llvm-svn: 158996

2 files changed, 8 insertions, 1 deletions

diff --git a/compiler-rt/lib/divsi3.c b/compiler-rt/lib/divsi3.c
index 0d81cb80c37..44573db37d5 100644
--- a/compiler-rt/lib/divsi3.c
+++ b/compiler-rt/lib/divsi3.c
@@ -29,5 +29,11 @@ __divsi3(si_int a, si_int b)
     a = (a ^ s_a) - s_a;                         /* negate if s_a == -1 */
     b = (b ^ s_b) - s_b;                         /* negate if s_b == -1 */
     s_a ^= s_b;                                  /* sign of quotient */
-    return (__udivsi3(a, b) ^ s_a) - s_a;        /* negate if s_a == -1 */
+    /*
+     * On CPUs without unsigned hardware division support,
+     *  this calls __udivsi3 (notice the cast to su_int).
+     * On CPUs with unsigned hardware division support,
+     *  this uses the unsigned division instruction.
+     */
+    return ((su_int)a/(su_int)b ^ s_a) - s_a;    /* negate if s_a == -1 */
 }
diff --git a/compiler-rt/lib/udivsi3.c b/compiler-rt/lib/udivsi3.c
index 39ef48bea65..ba011220bb4 100644
--- a/compiler-rt/lib/udivsi3.c
+++ b/compiler-rt/lib/udivsi3.c
@@ -20,6 +20,7 @@
 
 ARM_EABI_FNALIAS(uidiv, udivsi3);
 
+/* This function should not call __divsi3! */
 COMPILER_RT_ABI su_int
 __udivsi3(su_int n, su_int d)
 {