[PATCH-for-8.0,2/7] hw/mips/bootloader: Pass 32-bit immediate value to LUI opcode generator

Commit Message

Philippe Mathieu-Daudé Dec. 10, 2022, 3:54 p.m. UTC

While 32-bit wide instructions ISA restricts LUI to a 16-bit
immediate value, some 16-bit ones allow up to 20-bit immediate
(in particular nanoMIPS).

Signed-off-by: Philippe Mathieu-Daudé <[e-mail]>
---
 hw/mips/bootloader.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

Comments

Richard Henderson Dec. 11, 2022, 3:57 p.m. UTC | #1

On 12/10/22 09:54, Philippe Mathieu-Daudé wrote:
> -static void bl_gen_lui(void **p, bl_reg rt, uint16_t imm)
> +static void bl_gen_lui(void **p, bl_reg rt, uint32_t imm32)
>   {
>       /* R6: It's a alias of AUI with RS = 0 */
> -    bl_gen_i_type(p, 0x0f, 0, rt, imm);
> +    assert(imm32 <= UINT16_MAX);
> +    bl_gen_i_type(p, 0x0f, 0, rt, extract32(imm32, 16, 16));

This assert is obviously incorrect.  You wanted to test

    (imm32 & 0xffff) == 0


r~

Patch

diff --git a/hw/mips/bootloader.c b/hw/mips/bootloader.c
index fc14eb0894..3a4573118c 100644
--- a/hw/mips/bootloader.c
+++ b/hw/mips/bootloader.c
@@ -116,10 +116,11 @@  static void bl_gen_jalr(void **p, bl_reg rs)
     bl_gen_r_type(p, 0, rs, 0, BL_REG_RA, 0, 0x09);
 }
 
-static void bl_gen_lui(void **p, bl_reg rt, uint16_t imm)
+static void bl_gen_lui(void **p, bl_reg rt, uint32_t imm32)
 {
     /* R6: It's a alias of AUI with RS = 0 */
-    bl_gen_i_type(p, 0x0f, 0, rt, imm);
+    assert(imm32 <= UINT16_MAX);
+    bl_gen_i_type(p, 0x0f, 0, rt, extract32(imm32, 16, 16));
 }
 
 static void bl_gen_ori(void **p, bl_reg rt, bl_reg rs, uint16_t imm)
@@ -142,10 +143,10 @@  static void bl_gen_sd(void **p, bl_reg rt, uint8_t base, uint16_t offset)
 }
 
 /* Pseudo instructions */
-static void bl_gen_li(void **p, bl_reg rt, uint32_t imm)
+static void bl_gen_li(void **p, bl_reg rt, uint32_t imm32)
 {
-    bl_gen_lui(p, rt, extract32(imm, 16, 16));
-    bl_gen_ori(p, rt, rt, extract32(imm, 0, 16));
+    bl_gen_lui(p, rt, imm32);
+    bl_gen_ori(p, rt, rt, extract32(imm32, 0, 16));
 }
 
 static void bl_gen_dli(void **p, bl_reg rt, uint64_t imm)