[Qemu-devel] [PATCH v2 4/6] tcg/mips: Support r6 JR encoding

[James Hogan <james.hogan@imgtec.com>]

MIPSr6 encodes JR as JALR with zero as the link register, and the pre-r6
JR encoding is removed. Update TCG to use the new encoding when built
for r6.

We still use the old encoding for pre-r6, so as not to confuse return
prediction stack hardware which may detect only particular encodings of
the return instruction.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Cc: Aurelien Jarno <aurelien@aurel32.net>
---
Changes in v2:
- Turn #define into enum (Richard).
---
 tcg/mips/tcg-target.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tcg/mips/tcg-target.c b/tcg/mips/tcg-target.c
index 4305af967326..c08418c413d7 100644
--- a/tcg/mips/tcg-target.c
+++ b/tcg/mips/tcg-target.c
@@ -288,7 +288,7 @@ typedef enum {
     OPC_SRLV     = OPC_SPECIAL | 0x06,
     OPC_ROTRV    = OPC_SPECIAL | (0x01 <<  6) | 0x06,
     OPC_SRAV     = OPC_SPECIAL | 0x07,
-    OPC_JR       = OPC_SPECIAL | 0x08,
+    OPC_JR_R5    = OPC_SPECIAL | 0x08,
     OPC_JALR     = OPC_SPECIAL | 0x09,
     OPC_MOVZ     = OPC_SPECIAL | 0x0A,
     OPC_MOVN     = OPC_SPECIAL | 0x0B,
@@ -320,6 +320,9 @@ typedef enum {
     OPC_WSBH     = OPC_SPECIAL3 | 0x0a0,
     OPC_SEB      = OPC_SPECIAL3 | 0x420,
     OPC_SEH      = OPC_SPECIAL3 | 0x620,
+
+    /* MIPS r6 doesn't have JR, JALR should be used instead */
+    OPC_JR       = use_mips32r6_instructions ? OPC_JALR : OPC_JR_R5,
 } MIPSInsn;
 
 /*
-- 
2.4.9