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[PULL,39/47] tcg/riscv: Remove branch-over-branch fallback

Message ID 20210107201448.1152301-40-richard.henderson@linaro.org
State Accepted
Commit 4b6a52d01e0dd640dd15f79264b38790023e3587
Headers show
Series tcg patch queue | expand

Commit Message

Richard Henderson Jan. 7, 2021, 8:14 p.m. UTC 
Since 7ecd02a06f8, we are prepared to re-start code generation
with a smaller TB if a relocation is out of range.  We no longer
need to leave a nop in the stream Just In Case.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

---
 tcg/riscv/tcg-target.c.inc | 56 ++++----------------------------------
 1 file changed, 6 insertions(+), 50 deletions(-)

-- 
2.25.1
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Patch

diff --git a/tcg/riscv/tcg-target.c.inc b/tcg/riscv/tcg-target.c.inc
index 5b4c500a4b..34bee9c5a7 100644
--- a/tcg/riscv/tcg-target.c.inc
+++ b/tcg/riscv/tcg-target.c.inc
@@ -469,43 +469,16 @@  static bool reloc_call(tcg_insn_unit *code_ptr, const tcg_insn_unit *target)
 static bool patch_reloc(tcg_insn_unit *code_ptr, int type,
                         intptr_t value, intptr_t addend)
 {
-    uint32_t insn = *code_ptr;
-    intptr_t diff;
-    bool short_jmp;
-
     tcg_debug_assert(addend == 0);
-
     switch (type) {
     case R_RISCV_BRANCH:
-        diff = value - (uintptr_t)code_ptr;
-        short_jmp = diff == sextreg(diff, 0, 12);
-        if (short_jmp) {
-            return reloc_sbimm12(code_ptr, (tcg_insn_unit *)value);
-        } else {
-            /* Invert the condition */
-            insn = insn ^ (1 << 12);
-            /* Clear the offset */
-            insn &= 0x01fff07f;
-            /* Set the offset to the PC + 8 */
-            insn |= encode_sbimm12(8);
-
-            /* Move forward */
-            code_ptr[0] = insn;
-
-            /* Overwrite the NOP with jal x0,value */
-            diff = value - (uintptr_t)(code_ptr + 1);
-            insn = encode_uj(OPC_JAL, TCG_REG_ZERO, diff);
-            code_ptr[1] = insn;
-
-            return true;
-        }
-        break;
+        return reloc_sbimm12(code_ptr, (tcg_insn_unit *)value);
     case R_RISCV_JAL:
         return reloc_jimm20(code_ptr, (tcg_insn_unit *)value);
     case R_RISCV_CALL:
         return reloc_call(code_ptr, (tcg_insn_unit *)value);
     default:
-        tcg_abort();
+        g_assert_not_reached();
     }
 }
 
@@ -779,21 +752,8 @@  static void tcg_out_brcond(TCGContext *s, TCGCond cond, TCGReg arg1,
         arg2 = t;
     }
 
-    if (l->has_value) {
-        intptr_t diff = tcg_pcrel_diff(s, l->u.value_ptr);
-        if (diff == sextreg(diff, 0, 12)) {
-            tcg_out_opc_branch(s, op, arg1, arg2, diff);
-        } else {
-            /* Invert the conditional branch.  */
-            tcg_out_opc_branch(s, op ^ (1 << 12), arg1, arg2, 8);
-            tcg_out_opc_jump(s, OPC_JAL, TCG_REG_ZERO, diff - 4);
-        }
-    } else {
-        tcg_out_reloc(s, s->code_ptr, R_RISCV_BRANCH, l, 0);
-        tcg_out_opc_branch(s, op, arg1, arg2, 0);
-        /* NOP to allow patching later */
-        tcg_out_opc_imm(s, OPC_ADDI, TCG_REG_ZERO, TCG_REG_ZERO, 0);
-    }
+    tcg_out_reloc(s, s->code_ptr, R_RISCV_BRANCH, l, 0);
+    tcg_out_opc_branch(s, op, arg1, arg2, 0);
 }
 
 static void tcg_out_setcond(TCGContext *s, TCGCond cond, TCGReg ret,
@@ -1009,8 +969,6 @@  static void tcg_out_tlb_load(TCGContext *s, TCGReg addrl,
     /* Compare masked address with the TLB entry. */
     label_ptr[0] = s->code_ptr;
     tcg_out_opc_branch(s, OPC_BNE, TCG_REG_TMP0, TCG_REG_TMP1, 0);
-    /* NOP to allow patching later */
-    tcg_out_opc_imm(s, OPC_ADDI, TCG_REG_ZERO, TCG_REG_ZERO, 0);
 
     /* TLB Hit - translate address using addend.  */
     if (TCG_TARGET_REG_BITS > TARGET_LONG_BITS) {
@@ -1054,8 +1012,7 @@  static bool tcg_out_qemu_ld_slow_path(TCGContext *s, TCGLabelQemuLdst *l)
     }
 
     /* resolve label address */
-    if (!patch_reloc(l->label_ptr[0], R_RISCV_BRANCH,
-                     (intptr_t) s->code_ptr, 0)) {
+    if (!reloc_sbimm12(l->label_ptr[0], s->code_ptr)) {
         return false;
     }
 
@@ -1089,8 +1046,7 @@  static bool tcg_out_qemu_st_slow_path(TCGContext *s, TCGLabelQemuLdst *l)
     }
 
     /* resolve label address */
-    if (!patch_reloc(l->label_ptr[0], R_RISCV_BRANCH,
-                     (intptr_t) s->code_ptr, 0)) {
+    if (!reloc_sbimm12(l->label_ptr[0], s->code_ptr)) {
         return false;
     }