Add inline lpeek_i() function for llvm

Using inline assembly can reduce binary file size due
to inlining and by the bypassing the calling convention. This is
currently a llvm/clang feature only and is for experiemtal use.

include/mega65/memory.h

@@ -72,6 +72,36 @@ __attribute__((leaf))
 #endif
 uint8_t lpeek(uint32_t address);
 
+#ifdef __llvm__
+/**
+ * @brief Inlined version of `lpeek()`
+ * @param ADDRESS 28-bit address; must be a compile-time constant.
+ * @returns Value at address
+ * @warning This function is experimental and may change/be removed in future versions
+ */
+inline uint8_t lpeek_i(const uint32_t ADDRESS)
+{
+    // Helper to (dis)assemble 32-bit int; optimizes out fully
+    const union {
+        uint32_t value;
+        uint8_t byte[4];
+    } adr = { ADDRESS };
+
+    uint8_t value;
+
+    __attribute__((leaf)) __asm__ volatile(
+        "ldz #%4        \n" // complete Q=AXYZ register
+        "stq __rc2      \n" // Q -> rc2-5
+        "ldz #0         \n"
+        "lda [__rc2], z \n"
+        : "=a"(value)
+        : "a"(adr.byte[0]), "x"(adr.byte[1]), "y"(adr.byte[2]), "i"(adr.byte[3])
+        : "rc2", "rc3", "rc4", "rc5", "p");
+
+    return value;
+}
+#endif
+
 uint8_t lpeek_debounced(uint32_t address);
 
 /**

tests/test-memory.c

@@ -11,6 +11,7 @@
  */
 #include <mega65/memory.h>
 #include <mega65/tests.h>
+#include <mega65/debug.h>
 #include <stdlib.h>
 #include <stdint.h>
 
@@ -21,6 +22,7 @@ int main(void)
     assert_eq(sizeof(struct dmagic_dmalist), 20);
 
     // PEEK and POKE macros
+    debug_msg("TEST: peek/poke macro");
     POKE(0x3000, 7);
     POKE(0x3001, 9);
     POKE(0x3002, 13);
@@ -29,45 +31,63 @@ int main(void)
     assert_eq(PEEK(0x3002), 13);
 
     // lcopy
+    debug_msg("TEST: lcopy()");
     lcopy(0x3000, 0x4000, 3);
     assert_eq(PEEK(0x4000), 7);
     assert_eq(PEEK(0x4001), 9);
     assert_eq(PEEK(0x4002), 13);
 
     // lpoke and lpeek
+    debug_msg("TEST: lpeek() and lpoke()");
     lpoke(0x4000, 13);
     assert_eq(lpeek(0x4000), 13);
+#ifdef __llvm__
+    assert_eq(lpeek_i(0x4000), 13);
+#endif
+
     lpoke(0x4001, 9);
     assert_eq(lpeek(0x4001), 9);
+#ifdef __llvm__
+    assert_eq(lpeek_i(0x4001), 9);
+#endif
+
     lpoke(0x4002, 7);
     assert_eq(lpeek(0x4002), 7);
-    assert_eq(501, 501);
+#ifdef __llvm__
+    assert_eq(lpeek_i(0x4002), 7);
+#endif
 
     // dma_poke and dma_peek
+    debug_msg("TEST: dma_poke() and dma_peek()");
     dma_poke(0x4000, 9);
     dma_poke(0x4001, 10);
     dma_poke(0x4002, 11);
     assert_eq(dma_peek(0x4000), 9);
     assert_eq(dma_peek(0x4001), 10);
     assert_eq(dma_peek(0x4002), 11);
 
+
     // lfill
+    debug_msg("TEST: lfill()");
     lfill(0x3000, 1, 3);
     assert_eq(PEEK(0x3000), 1);
     assert_eq(PEEK(0x3001), 1);
     assert_eq(PEEK(0x3002), 1);
 
     // lfill_skip
+    debug_msg("TEST: lfill() with skip");
     lfill_skip(0x3000, 0, 3, 2);
     assert_eq(PEEK(0x3000), 0);
     assert_eq(PEEK(0x3001), 1);
     assert_eq(PEEK(0x3002), 0);
 
     // POKE16 and PEEK16 macros
+    debug_msg("TEST: poke/peek 16");
     POKE16(0x3000, 0xAABB);
     assert_eq(PEEK16(0x3000), 0xAABB);
 
     // POKE32 and PEEK32 macros
+    debug_msg("TEST: poke/peek 32");
     POKE32(0x3000, 0xAABBCCDD);
     assert_eq(PEEK32(0x3000), 0xAABBCCDD);