* src/vm/jit/mips/emit.c (emit_branch): Implemented

AlwaysEmitLongBranches and unconditional long-branches.

diff --git a/src/vm/jit/mips/emit.c b/src/vm/jit/mips/emit.c
index 86fbb11c4bdefed381822b9f901d3c7ba3a485d2..fb41435ebd8bf88e3c02f9827346a2d2d3765c7f 100644 (file)
--- a/src/vm/jit/mips/emit.c
+++ b/src/vm/jit/mips/emit.c
@@ -378,20 +378,15 @@ void emit_lconst(codegendata *cd, s4 d, s8 value)
 
 void emit_branch(codegendata *cd, s4 disp, s4 condition, s4 reg, u4 opt)
 {
-       s4 checkdisp;
-       s4 branchdisp;
-
-       /* calculate the different displacements */
-
-       checkdisp  = (disp - 4);
-       branchdisp = (disp - 4) >> 2;
+       // Calculate the displacements.
+       int32_t checkdisp  = (disp - 4);
+       int32_t branchdisp = (disp - 4) >> 2;
 
        /* check which branch to generate */
 
        if (condition == BRANCH_UNCONDITIONAL) {
-               /* check displacement for overflow */
-
-               if ((checkdisp < (s4) 0xffff8000) || (checkdisp > (s4) 0x00007fff)) {
+               // Check displacement for overflow.
+               if (opt_AlwaysEmitLongBranches || ((checkdisp < (int32_t) 0xffff8000) || (checkdisp > (int32_t) 0x00007fff))) {
                        /* if the long-branches flag isn't set yet, do it */
 
                        if (!CODEGENDATA_HAS_FLAG_LONGBRANCHES(cd)) {
@@ -399,7 +394,20 @@ void emit_branch(codegendata *cd, s4 disp, s4 condition, s4 reg, u4 opt)
                                                          CODEGENDATA_FLAG_LONGBRANCHES);
                        }
 
-                       vm_abort("emit_branch: emit unconditional long-branch code");
+                       // Calculate the offset relative to PV.
+                       int32_t currentrpc = cd->mcodeptr - cd->mcodebase;
+                       int32_t offset     = currentrpc + disp;
+
+                       // Sanity check.
+                       assert(offset % 4 == 0);
+
+                       // Do the long-branch.
+                       M_LUI(REG_ITMP3, offset >> 16);
+                       M_OR_IMM(REG_ITMP3, offset, REG_ITMP3);
+                       M_AADD(REG_PV, REG_ITMP3, REG_ITMP3);
+                       M_JMP(REG_ITMP3);
+                       M_NOP;
+                       M_NOP; // This nop is to have 6 instructions (see BRANCH_NOPS).
                }
                else {
                        M_BR(branchdisp);
@@ -407,9 +415,8 @@ void emit_branch(codegendata *cd, s4 disp, s4 condition, s4 reg, u4 opt)
                }
        }
        else {
-               /* and displacement for overflow */
-
-               if ((checkdisp < (s4) 0xffff8000) || (checkdisp > (s4) 0x00007fff)) {
+               // Check displacement for overflow.
+               if (opt_AlwaysEmitLongBranches || ((checkdisp < (int32_t) 0xffff8000) || (checkdisp > (int32_t) 0x00007fff))) {
                        /* if the long-branches flag isn't set yet, do it */
 
                        if (!CODEGENDATA_HAS_FLAG_LONGBRANCHES(cd)) {
@@ -417,6 +424,14 @@ void emit_branch(codegendata *cd, s4 disp, s4 condition, s4 reg, u4 opt)
                                                          CODEGENDATA_FLAG_LONGBRANCHES);
                        }
 
+                       // Calculate the offset relative to PV before we generate
+                       // new code.
+                       int32_t currentrpc = cd->mcodeptr - cd->mcodebase;
+                       int32_t offset     = currentrpc + disp;
+
+                       // Sanity check.
+                       assert(offset % 4 == 0);
+
                        switch (condition) {
                        case BRANCH_EQ:
                                M_BNE(GET_HIGH_REG(reg), GET_LOW_REG(reg), 5);
@@ -440,15 +455,16 @@ void emit_branch(codegendata *cd, s4 disp, s4 condition, s4 reg, u4 opt)
                                vm_abort("emit_branch: unknown condition %d", condition);
                        }
 
-                       /* The actual branch code which is over-jumped (NOTE: we
-                          don't use a branch delay slot here). */
+                       // The actual branch code which is over-jumped.  NOTE: We
+                       // don't use a branch delay slot for the conditional
+                       // branch.
 
-                       M_LUI(REG_ITMP3, branchdisp >> 16);
-                       M_OR_IMM(REG_ITMP3, branchdisp, REG_ITMP3);
+                       // Do the long-branch.
+                       M_LUI(REG_ITMP3, offset >> 16);
+                       M_OR_IMM(REG_ITMP3, offset, REG_ITMP3);
                        M_AADD(REG_PV, REG_ITMP3, REG_ITMP3);
                        M_JMP(REG_ITMP3);
                        M_NOP;
-
                }
                else {
                        switch (condition) {