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diff --git a/openpower/sv/svp64.mdwn b/openpower/sv/svp64.mdwn
index d704266f60f98df579472623d09df435dc1cb535..4874e4f518e735835cf7e62f49e2faff000c3fa0 100644 (file)
--- a/openpower/sv/svp64.mdwn
+++ b/openpower/sv/svp64.mdwn
@@ -186,15 +186,20 @@ from Figure 97, Book I, Section 6.3, Page 258:
 ```
     #pragma pack
     typedef union {
+        uint8_t actual_bytes[8];
+        // all of these are very deliberately unbounded arrays
+        // that intentionally "wrap" into subsequent actual_bytes...
         uint8_t  bytes[]; // elwidth 8
         uint16_t hwords[]; // elwidth 16
         uint32_t words[]; // elwidth 32
         uint64_t dwords[]; // elwidth 64
-        uint8_t actual_bytes[8];
+
     } el_reg_t;
 
+    // ... here, as packed statically-defined GPRs.
     elreg_t int_regfile[128];
 
+    // use element 0 as the destination
     void get_register_element(el_reg_t* el, int gpr, int element, int width) {
         switch (width) {
             case 64: el->dwords[0] = int_regfile[gpr].dwords[element];
@@ -203,6 +208,8 @@ from Figure 97, Book I, Section 6.3, Page 258:
             case 8 : el->bytes[0] = int_regfile[gpr].bytes[element];
         }
     }
+
+    // use element 0 as the source
     void set_register_element(el_reg_t* el, int gpr, int element, int width) {
         switch (width) {
             case 64: int_regfile[gpr].dwords[element] = el->dwords[0];