Use union to pack constant value

tyfkda · Oct 13, 2023 · a44d396 · a44d396
1 parent 054fda0
commit a44d396
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Showing 2 changed files with 13 additions and 7 deletions.
diff --git a/src/cc/backend/ir.h b/src/cc/backend/ir.h
@@ -38,12 +38,19 @@ enum VRegSize {
 
 typedef struct VReg {
   enum VRegSize vsize;
-  int virt;         // Virtual reg no.
-  int phys;         // Physical reg no.
   int flag;
-  int reg_param_index;  // Index of function parameter through register: -1=not a register param.
-  int64_t fixnum;   // Constant value.
-  FrameInfo frame;  // FrameInfo for spilled register.
+  union {
+    // Non-const:
+    struct {
+      int virt;             // Virtual reg no.
+      int phys;             // Physical reg no.
+      int reg_param_index;  // Index of function parameter through register: -1=non reg param.
+      FrameInfo frame;      // FrameInfo for spilled register.
+    };
+
+    // Const:
+    int64_t fixnum;   // Constant value.
+  };
 } VReg;
 
 void spill_vreg(VReg *vreg);

diff --git a/src/cc/backend/regalloc.c b/src/cc/backend/regalloc.c
@@ -29,7 +29,6 @@ static VReg *alloc_vreg(enum VRegSize vsize, int vflag) {
   VReg *vreg = malloc_or_die(sizeof(*vreg));
   vreg->virt = -1;
   vreg->phys = -1;
-  vreg->fixnum = 0;
   vreg->vsize = vsize;
   vreg->flag = vflag;
   vreg->reg_param_index = -1;
@@ -169,7 +168,7 @@ static void check_live_interval(BBContainer *bbcon, int vreg_count, LiveInterval
       VReg *vregs[] = {ir->dst, ir->opr1, ir->opr2};
       for (int k = 0; k < 3; ++k) {
         VReg *vreg = vregs[k];
-        if (vreg == NULL)
+        if (vreg == NULL || (vreg->flag & VRF_CONST))
           continue;
         LiveInterval *li = &intervals[vreg->virt];
         if (li->start < 0 && !(vreg->flag & VRF_PARAM))