[PATCH 1/2] powerpc: Fix 0 vs. r0 confusion in X/D-form instructions
J. Neuschäfer via B4 Relay
devnull+j.ne.posteo.net at kernel.org
Thu Dec 12 18:05:46 CET 2024
From: "J. Neuschäfer" <j.ne at posteo.net>
Instructions such as dcbi are in the X-form; they have RA and RB fields
and the effective address (EA) is computed as (RA|0)+(RB). In words,
this means that if RA is zero, the left-hand side of the addition is
zero, otherwise the corresponding GPR is used. r0 can never be used on
the left-hand side of a X-form instruction.
For D-form instructions such as addis, the Power ISA illustrates this in
the instruction pseudo-code:
if RA = 0 then RT <- EXTS(SI || 0x0000)
else RT <- (RA) + EXIS(SI || 0x0000)
In all of these cases, RA=0 indicates the value zero, not register r0.
I verified with gazerbeam_defconfig (MPC83xx) and qemu-ppce500_defconfig
(MPC85xx) that this patch results in the same machine code.
Signed-off-by: J. Neuschäfer <j.ne at posteo.net>
---
arch/powerpc/cpu/mpc83xx/start.S | 72 ++++++++++++++++++++--------------------
arch/powerpc/cpu/mpc85xx/start.S | 24 +++++++-------
arch/powerpc/lib/ppccache.S | 6 ++--
3 files changed, 51 insertions(+), 51 deletions(-)
diff --git a/arch/powerpc/cpu/mpc83xx/start.S b/arch/powerpc/cpu/mpc83xx/start.S
index 78762f000dfd35568838654e11c2bc38a5b40e90..0d8bc4641176b9c5e45158b8455e1989de0c3b91 100644
--- a/arch/powerpc/cpu/mpc83xx/start.S
+++ b/arch/powerpc/cpu/mpc83xx/start.S
@@ -550,133 +550,133 @@ init_e300_core: /* time t 10 */
/* setup_bats - set them up to some initial state */
.globl setup_bats
setup_bats:
- addis r0, r0, 0x0000
+ addis r0, 0, 0x0000
/* IBAT 0 */
- addis r4, r0, CFG_SYS_IBAT0L at h
+ addis r4, 0, CFG_SYS_IBAT0L at h
ori r4, r4, CFG_SYS_IBAT0L at l
- addis r3, r0, CFG_SYS_IBAT0U at h
+ addis r3, 0, CFG_SYS_IBAT0U at h
ori r3, r3, CFG_SYS_IBAT0U at l
mtspr IBAT0L, r4
mtspr IBAT0U, r3
/* DBAT 0 */
- addis r4, r0, CFG_SYS_DBAT0L at h
+ addis r4, 0, CFG_SYS_DBAT0L at h
ori r4, r4, CFG_SYS_DBAT0L at l
- addis r3, r0, CFG_SYS_DBAT0U at h
+ addis r3, 0, CFG_SYS_DBAT0U at h
ori r3, r3, CFG_SYS_DBAT0U at l
mtspr DBAT0L, r4
mtspr DBAT0U, r3
/* IBAT 1 */
- addis r4, r0, CFG_SYS_IBAT1L at h
+ addis r4, 0, CFG_SYS_IBAT1L at h
ori r4, r4, CFG_SYS_IBAT1L at l
- addis r3, r0, CFG_SYS_IBAT1U at h
+ addis r3, 0, CFG_SYS_IBAT1U at h
ori r3, r3, CFG_SYS_IBAT1U at l
mtspr IBAT1L, r4
mtspr IBAT1U, r3
/* DBAT 1 */
- addis r4, r0, CFG_SYS_DBAT1L at h
+ addis r4, 0, CFG_SYS_DBAT1L at h
ori r4, r4, CFG_SYS_DBAT1L at l
- addis r3, r0, CFG_SYS_DBAT1U at h
+ addis r3, 0, CFG_SYS_DBAT1U at h
ori r3, r3, CFG_SYS_DBAT1U at l
mtspr DBAT1L, r4
mtspr DBAT1U, r3
/* IBAT 2 */
- addis r4, r0, CFG_SYS_IBAT2L at h
+ addis r4, 0, CFG_SYS_IBAT2L at h
ori r4, r4, CFG_SYS_IBAT2L at l
- addis r3, r0, CFG_SYS_IBAT2U at h
+ addis r3, 0, CFG_SYS_IBAT2U at h
ori r3, r3, CFG_SYS_IBAT2U at l
mtspr IBAT2L, r4
mtspr IBAT2U, r3
/* DBAT 2 */
- addis r4, r0, CFG_SYS_DBAT2L at h
+ addis r4, 0, CFG_SYS_DBAT2L at h
ori r4, r4, CFG_SYS_DBAT2L at l
- addis r3, r0, CFG_SYS_DBAT2U at h
+ addis r3, 0, CFG_SYS_DBAT2U at h
ori r3, r3, CFG_SYS_DBAT2U at l
mtspr DBAT2L, r4
mtspr DBAT2U, r3
/* IBAT 3 */
- addis r4, r0, CFG_SYS_IBAT3L at h
+ addis r4, 0, CFG_SYS_IBAT3L at h
ori r4, r4, CFG_SYS_IBAT3L at l
- addis r3, r0, CFG_SYS_IBAT3U at h
+ addis r3, 0, CFG_SYS_IBAT3U at h
ori r3, r3, CFG_SYS_IBAT3U at l
mtspr IBAT3L, r4
mtspr IBAT3U, r3
/* DBAT 3 */
- addis r4, r0, CFG_SYS_DBAT3L at h
+ addis r4, 0, CFG_SYS_DBAT3L at h
ori r4, r4, CFG_SYS_DBAT3L at l
- addis r3, r0, CFG_SYS_DBAT3U at h
+ addis r3, 0, CFG_SYS_DBAT3U at h
ori r3, r3, CFG_SYS_DBAT3U at l
mtspr DBAT3L, r4
mtspr DBAT3U, r3
#ifdef CONFIG_HIGH_BATS
/* IBAT 4 */
- addis r4, r0, CFG_SYS_IBAT4L at h
+ addis r4, 0, CFG_SYS_IBAT4L at h
ori r4, r4, CFG_SYS_IBAT4L at l
- addis r3, r0, CFG_SYS_IBAT4U at h
+ addis r3, 0, CFG_SYS_IBAT4U at h
ori r3, r3, CFG_SYS_IBAT4U at l
mtspr IBAT4L, r4
mtspr IBAT4U, r3
/* DBAT 4 */
- addis r4, r0, CFG_SYS_DBAT4L at h
+ addis r4, 0, CFG_SYS_DBAT4L at h
ori r4, r4, CFG_SYS_DBAT4L at l
- addis r3, r0, CFG_SYS_DBAT4U at h
+ addis r3, 0, CFG_SYS_DBAT4U at h
ori r3, r3, CFG_SYS_DBAT4U at l
mtspr DBAT4L, r4
mtspr DBAT4U, r3
/* IBAT 5 */
- addis r4, r0, CFG_SYS_IBAT5L at h
+ addis r4, 0, CFG_SYS_IBAT5L at h
ori r4, r4, CFG_SYS_IBAT5L at l
- addis r3, r0, CFG_SYS_IBAT5U at h
+ addis r3, 0, CFG_SYS_IBAT5U at h
ori r3, r3, CFG_SYS_IBAT5U at l
mtspr IBAT5L, r4
mtspr IBAT5U, r3
/* DBAT 5 */
- addis r4, r0, CFG_SYS_DBAT5L at h
+ addis r4, 0, CFG_SYS_DBAT5L at h
ori r4, r4, CFG_SYS_DBAT5L at l
- addis r3, r0, CFG_SYS_DBAT5U at h
+ addis r3, 0, CFG_SYS_DBAT5U at h
ori r3, r3, CFG_SYS_DBAT5U at l
mtspr DBAT5L, r4
mtspr DBAT5U, r3
/* IBAT 6 */
- addis r4, r0, CFG_SYS_IBAT6L at h
+ addis r4, 0, CFG_SYS_IBAT6L at h
ori r4, r4, CFG_SYS_IBAT6L at l
- addis r3, r0, CFG_SYS_IBAT6U at h
+ addis r3, 0, CFG_SYS_IBAT6U at h
ori r3, r3, CFG_SYS_IBAT6U at l
mtspr IBAT6L, r4
mtspr IBAT6U, r3
/* DBAT 6 */
- addis r4, r0, CFG_SYS_DBAT6L at h
+ addis r4, 0, CFG_SYS_DBAT6L at h
ori r4, r4, CFG_SYS_DBAT6L at l
- addis r3, r0, CFG_SYS_DBAT6U at h
+ addis r3, 0, CFG_SYS_DBAT6U at h
ori r3, r3, CFG_SYS_DBAT6U at l
mtspr DBAT6L, r4
mtspr DBAT6U, r3
/* IBAT 7 */
- addis r4, r0, CFG_SYS_IBAT7L at h
+ addis r4, 0, CFG_SYS_IBAT7L at h
ori r4, r4, CFG_SYS_IBAT7L at l
- addis r3, r0, CFG_SYS_IBAT7U at h
+ addis r3, 0, CFG_SYS_IBAT7U at h
ori r3, r3, CFG_SYS_IBAT7U at l
mtspr IBAT7L, r4
mtspr IBAT7U, r3
/* DBAT 7 */
- addis r4, r0, CFG_SYS_DBAT7L at h
+ addis r4, 0, CFG_SYS_DBAT7L at h
ori r4, r4, CFG_SYS_DBAT7L at l
- addis r3, r0, CFG_SYS_DBAT7U at h
+ addis r3, 0, CFG_SYS_DBAT7U at h
ori r3, r3, CFG_SYS_DBAT7U at l
mtspr DBAT7L, r4
mtspr DBAT7U, r3
@@ -1057,7 +1057,7 @@ lock_ram_in_cache:
(CFG_SYS_INIT_RAM_ADDR & 31) + 31) / 32
mtctr r4
1:
- dcbz r0, r3
+ dcbz 0, r3
addi r3, r3, 32
bdnz 1b
@@ -1078,8 +1078,8 @@ unlock_ram_in_cache:
li r4, ((CFG_SYS_INIT_RAM_SIZE & ~31) + \
(CFG_SYS_INIT_RAM_ADDR & 31) + 31) / 32
mtctr r4
-1: icbi r0, r3
- dcbi r0, r3
+1: icbi 0, r3
+ dcbi 0, r3
addi r3, r3, 32
bdnz 1b
sync /* Wait for all icbi to complete on bus */
diff --git a/arch/powerpc/cpu/mpc85xx/start.S b/arch/powerpc/cpu/mpc85xx/start.S
index 89bce5bed693e47f09015c0f50de9176e17badc1..5234e42dc28b1ff4ea7f003aee2ee8bb5bc2cf65 100644
--- a/arch/powerpc/cpu/mpc85xx/start.S
+++ b/arch/powerpc/cpu/mpc85xx/start.S
@@ -1203,12 +1203,12 @@ switch_as:
mtctr r2
li r0,0
1:
- dcbz r0,r3
+ dcbz 0,r3
#ifdef CONFIG_E6500 /* Lock/unlock L2 cache long with L1 */
- dcbtls 2, r0, r3
- dcbtls 0, r0, r3
+ dcbtls 2, 0, r3
+ dcbtls 0, 0, r3
#else
- dcbtls 0, r0, r3
+ dcbtls 0, 0, r3
#endif
addi r3,r3,CONFIG_SYS_CACHELINE_SIZE
bdnz 1b
@@ -1514,7 +1514,7 @@ out16:
/*------------------------------------------------------------------------------- */
.globl out16r
out16r:
- sthbrx r4,r0,r3
+ sthbrx r4,0,r3
sync
blr
@@ -1534,7 +1534,7 @@ out32:
/*------------------------------------------------------------------------------- */
.globl out32r
out32r:
- stwbrx r4,r0,r3
+ stwbrx r4,0,r3
sync
blr
@@ -1553,7 +1553,7 @@ in16:
/*------------------------------------------------------------------------------- */
.globl in16r
in16r:
- lhbrx r3,r0,r3
+ lhbrx r3,0,r3
blr
/*------------------------------------------------------------------------------- */
@@ -1571,7 +1571,7 @@ in32:
/*------------------------------------------------------------------------------- */
.globl in32r
in32r:
- lwbrx r3,r0,r3
+ lwbrx r3,0,r3
blr
#endif /* !MINIMAL_SPL */
@@ -1832,12 +1832,12 @@ unlock_ram_in_cache:
andi. r4,r4,0x1ff
slwi r4,r4,(10 - 1 - L1_CACHE_SHIFT)
mtctr r4
-1: dcbi r0,r3
+1: dcbi 0,r3
#ifdef CONFIG_E6500 /* lock/unlock L2 cache long with L1 */
- dcblc 2, r0, r3
- dcblc 0, r0, r3
+ dcblc 2, 0, r3
+ dcblc 0, 0, r3
#else
- dcblc r0,r3
+ dcblc 0,r3
#endif
addi r3,r3,CONFIG_SYS_CACHELINE_SIZE
bdnz 1b
diff --git a/arch/powerpc/lib/ppccache.S b/arch/powerpc/lib/ppccache.S
index e55025181f76fd4b9bdef79db46ddea29c049b99..e94b40ead63d83dab0403ef842f281ddd50bb7ea 100644
--- a/arch/powerpc/lib/ppccache.S
+++ b/arch/powerpc/lib/ppccache.S
@@ -20,7 +20,7 @@
/*------------------------------------------------------------------------------- */
.globl ppcDcbf
ppcDcbf:
- dcbf r0,r3
+ dcbf 0,r3
blr
/*------------------------------------------------------------------------------- */
@@ -31,7 +31,7 @@ ppcDcbf:
/*------------------------------------------------------------------------------- */
.globl ppcDcbi
ppcDcbi:
- dcbi r0,r3
+ dcbi 0,r3
blr
/*--------------------------------------------------------------------------
@@ -43,7 +43,7 @@ ppcDcbi:
.globl ppcDcbz
ppcDcbz:
- dcbz r0,r3
+ dcbz 0,r3
blr
/*------------------------------------------------------------------------------- */
--
2.45.2
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