Add an ASSUME macro that requires a true condition

4 files changed, 23 insertions, 0 deletions

diff --git a/Alc/mixer/mixer_c.c b/Alc/mixer/mixer_c.c
index e40c2cad..ee667671 100644
--- a/Alc/mixer/mixer_c.c
+++ b/Alc/mixer/mixer_c.c
@@ -65,6 +65,8 @@ const ALfloat *Resample_bsinc_C(const InterpState *state, const ALfloat *restric
     ALsizei j_f, pi, i;
     ALfloat pf, r;
 
+    ASSUME(m > 0);
+
     src += state->bsinc.l;
     for(i = 0;i < dstlen;i++)
     {
diff --git a/Alc/mixer/mixer_neon.c b/Alc/mixer/mixer_neon.c
index 7f8dd1d4..e8a85f71 100644
--- a/Alc/mixer/mixer_neon.c
+++ b/Alc/mixer/mixer_neon.c
@@ -78,6 +78,8 @@ const ALfloat *Resample_bsinc_Neon(const InterpState *state,
     float32x4_t r4;
     ALfloat pf;
 
+    ASSUME(m > 0);
+
     src += state->bsinc.l;
     for(i = 0;i < dstlen;i++)
     {
diff --git a/Alc/mixer/mixer_sse.c b/Alc/mixer/mixer_sse.c
index c9615c25..5c181c75 100644
--- a/Alc/mixer/mixer_sse.c
+++ b/Alc/mixer/mixer_sse.c
@@ -24,6 +24,8 @@ const ALfloat *Resample_bsinc_SSE(const InterpState *state, const ALfloat *restr
     ALfloat pf;
     __m128 r4;
 
+    ASSUME(m > 0);
+
     src += state->bsinc.l;
     for(i = 0;i < dstlen;i++)
     {
diff --git a/OpenAL32/Include/alMain.h b/OpenAL32/Include/alMain.h
index 783a90de..77144a29 100644
--- a/OpenAL32/Include/alMain.h
+++ b/OpenAL32/Include/alMain.h
@@ -42,11 +42,28 @@
 
 
 #ifdef __GNUC__
+/* LIKELY optimizes the case where the condition is true. The condition is not
+ * required to be true, but it can result in more optimal code for the true
+ * path at the expense of a less optimal false path.
+ */
 #define LIKELY(x) __builtin_expect(!!(x), !0)
+/* The opposite of LIKELY, optimizing the case where the condition is false. */
 #define UNLIKELY(x) __builtin_expect(!!(x), 0)
+/* Unlike LIKELY, ASSUME requires the condition to be true or else it invokes
+ * undefined behavior. It's essentially an assert without actually checking the
+ * condition at run-time, allowing for stronger optimizations than LIKELY.
+ */
+#define ASSUME(x) do { if(!(x)) __builtin_unreachable(); } while(0)
+
 #else
+
 #define LIKELY(x) (!!(x))
 #define UNLIKELY(x) (!!(x))
+#ifdef _MSC_VER
+#define ASSUME __assume
+#else
+#define ASSUME(x) ((void)0)
+#endif
 #endif
 
 #ifndef UINT64_MAX