[PATCH] tcg/ppc: Use TCG_REG_TMP2 for scratch index in prepare_host_addr

[PATCH] tcg/ppc: Use TCG_REG_TMP2 for scratch index in prepare_host_addr

[Richard Henderson]

In tcg_out_qemu_ldst_i128, we need a non-zero index register,
which we then use as a base register in several address modes.
Since we always have TCG_REG_TMP2 available, use that.

In tcg_out_qemu_st, in the fallback when STDBRX is not available,
avoid clobbering TCG_REG_TMP1, which might be h.base, which is
still in use.  Use TCG_REG_TMP2 instead.  Since the final use of
h.index is that ADDI, there is no conflict with the above.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2597
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 tcg/ppc/tcg-target.c.inc | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tcg/ppc/tcg-target.c.inc b/tcg/ppc/tcg-target.c.inc
index 3f413ce3c1..223f079524 100644
--- a/tcg/ppc/tcg-target.c.inc
+++ b/tcg/ppc/tcg-target.c.inc
@@ -2617,8 +2617,8 @@ static TCGLabelQemuLdst *prepare_host_addr(TCGContext *s, HostAddress *h,
 
     if (TCG_TARGET_REG_BITS == 64 && addr_type == TCG_TYPE_I32) {
         /* Zero-extend the guest address for use in the host address. */
-        tcg_out_ext32u(s, TCG_REG_R0, addrlo);
-        h->index = TCG_REG_R0;
+        tcg_out_ext32u(s, TCG_REG_TMP2, addrlo);
+        h->index = TCG_REG_TMP2;
     } else {
         h->index = addrlo;
     }
@@ -2704,9 +2704,9 @@ static void tcg_out_qemu_st(TCGContext *s, TCGReg datalo, TCGReg datahi,
         uint32_t insn = qemu_stx_opc[opc & (MO_BSWAP | MO_SIZE)];
         if (!have_isa_2_06 && insn == STDBRX) {
             tcg_out32(s, STWBRX | SAB(datalo, h.base, h.index));
-            tcg_out32(s, ADDI | TAI(TCG_REG_TMP1, h.index, 4));
+            tcg_out32(s, ADDI | TAI(TCG_REG_TMP2, h.index, 4));
             tcg_out_shri64(s, TCG_REG_R0, datalo, 32);
-            tcg_out32(s, STWBRX | SAB(TCG_REG_R0, h.base, TCG_REG_TMP1));
+            tcg_out32(s, STWBRX | SAB(TCG_REG_R0, h.base, TCG_REG_TMP2));
         } else {
             tcg_out32(s, insn | SAB(datalo, h.base, h.index));
         }
-- 
2.43.0

Re: [PATCH] tcg/ppc: Use TCG_REG_TMP2 for scratch index in prepare_host_addr

[Michael Tokarev]

06.10.2024 01:15, Richard Henderson wrote:
> In tcg_out_qemu_ldst_i128, we need a non-zero index register,
> which we then use as a base register in several address modes.
> Since we always have TCG_REG_TMP2 available, use that.
> 
> In tcg_out_qemu_st, in the fallback when STDBRX is not available,
> avoid clobbering TCG_REG_TMP1, which might be h.base, which is
> still in use.  Use TCG_REG_TMP2 instead.  Since the final use of
> h.index is that ADDI, there is no conflict with the above.
> 
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2597
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Fixes: v8.0.0-524-ge3867bad0d "tcg/ppc: Introduce HostAddress"
Fixes: v8.0.0-744-g01a112e2e9 "tcg/ppc: Reorg tcg_out_tlb_read"
Tested-By: Michael Tokarev <mjt@tls.msk.ru>

Also noted for -stable.

Thank you!

/mjt