[PATCH v4] Make iwmmxt.S support Clang's integrated assembler

[Jian Cai <jiancai@google.com>]

This patch replaces 6 IWMMXT instructions Clang's integrated assembler
does not support in iwmmxt.S using macros, while making sure GNU
assembler still emit the same instructions. This should be easier than
providing full IWMMXT support in Clang.  This is one of the last bits of
kernel code that could be compiled but not assembled with clang. Once
all of it works with IAS, we no longer need to special-case 32-bit Arm
in Kbuild, or turn off CONFIG_IWMMXT when build-testing.

"Intel Wireless MMX Technology - Developer Guide - August, 2002" should
be referenced for the encoding schemes of these extensions.

Link: https://github.com/ClangBuiltLinux/linux/issues/975

Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Jian Cai <jiancai@google.com>
---

Changes v3 -> v4:
Forgot to include iwmmxt.h in v3.

 arch/arm/kernel/iwmmxt.S | 89 ++++++++++++++++++++--------------------
 arch/arm/kernel/iwmmxt.h | 47 +++++++++++++++++++++
 2 files changed, 92 insertions(+), 44 deletions(-)
 create mode 100644 arch/arm/kernel/iwmmxt.h

diff --git a/arch/arm/kernel/iwmmxt.S b/arch/arm/kernel/iwmmxt.S
index 0dcae787b004..d2b4ac06e4ed 100644
--- a/arch/arm/kernel/iwmmxt.S
+++ b/arch/arm/kernel/iwmmxt.S
@@ -16,6 +16,7 @@
 #include <asm/thread_info.h>
 #include <asm/asm-offsets.h>
 #include <asm/assembler.h>
+#include "iwmmxt.h"
 
 #if defined(CONFIG_CPU_PJ4) || defined(CONFIG_CPU_PJ4B)
 #define PJ4(code...)		code
@@ -113,33 +114,33 @@ concan_save:
 
 concan_dump:
 
-	wstrw	wCSSF, [r1, #MMX_WCSSF]
-	wstrw	wCASF, [r1, #MMX_WCASF]
-	wstrw	wCGR0, [r1, #MMX_WCGR0]
-	wstrw	wCGR1, [r1, #MMX_WCGR1]
-	wstrw	wCGR2, [r1, #MMX_WCGR2]
-	wstrw	wCGR3, [r1, #MMX_WCGR3]
+	wstrw	wCSSF, r1, MMX_WCSSF
+	wstrw	wCASF, r1, MMX_WCASF
+	wstrw	wCGR0, r1, MMX_WCGR0
+	wstrw	wCGR1, r1, MMX_WCGR1
+	wstrw	wCGR2, r1, MMX_WCGR2
+	wstrw	wCGR3, r1, MMX_WCGR3
 
 1:	@ MUP? wRn
 	tst	r2, #0x2
 	beq	2f
 
-	wstrd	wR0,  [r1, #MMX_WR0]
-	wstrd	wR1,  [r1, #MMX_WR1]
-	wstrd	wR2,  [r1, #MMX_WR2]
-	wstrd	wR3,  [r1, #MMX_WR3]
-	wstrd	wR4,  [r1, #MMX_WR4]
-	wstrd	wR5,  [r1, #MMX_WR5]
-	wstrd	wR6,  [r1, #MMX_WR6]
-	wstrd	wR7,  [r1, #MMX_WR7]
-	wstrd	wR8,  [r1, #MMX_WR8]
-	wstrd	wR9,  [r1, #MMX_WR9]
-	wstrd	wR10, [r1, #MMX_WR10]
-	wstrd	wR11, [r1, #MMX_WR11]
-	wstrd	wR12, [r1, #MMX_WR12]
-	wstrd	wR13, [r1, #MMX_WR13]
-	wstrd	wR14, [r1, #MMX_WR14]
-	wstrd	wR15, [r1, #MMX_WR15]
+	wstrd	wR0,  r1, MMX_WR0
+	wstrd	wR1,  r1, MMX_WR1
+	wstrd	wR2,  r1, MMX_WR2
+	wstrd	wR3,  r1, MMX_WR3
+	wstrd	wR4,  r1, MMX_WR4
+	wstrd	wR5,  r1, MMX_WR5
+	wstrd	wR6,  r1, MMX_WR6
+	wstrd	wR7,  r1, MMX_WR7
+	wstrd	wR8,  r1, MMX_WR8
+	wstrd	wR9,  r1, MMX_WR9
+	wstrd	wR10, r1, MMX_WR10
+	wstrd	wR11, r1, MMX_WR11
+	wstrd	wR12, r1, MMX_WR12
+	wstrd	wR13, r1, MMX_WR13
+	wstrd	wR14, r1, MMX_WR14
+	wstrd	wR15, r1, MMX_WR15
 
 2:	teq	r0, #0				@ anything to load?
 	reteq	lr				@ if not, return
@@ -147,30 +148,30 @@ concan_dump:
 concan_load:
 
 	@ Load wRn
-	wldrd	wR0,  [r0, #MMX_WR0]
-	wldrd	wR1,  [r0, #MMX_WR1]
-	wldrd	wR2,  [r0, #MMX_WR2]
-	wldrd	wR3,  [r0, #MMX_WR3]
-	wldrd	wR4,  [r0, #MMX_WR4]
-	wldrd	wR5,  [r0, #MMX_WR5]
-	wldrd	wR6,  [r0, #MMX_WR6]
-	wldrd	wR7,  [r0, #MMX_WR7]
-	wldrd	wR8,  [r0, #MMX_WR8]
-	wldrd	wR9,  [r0, #MMX_WR9]
-	wldrd	wR10, [r0, #MMX_WR10]
-	wldrd	wR11, [r0, #MMX_WR11]
-	wldrd	wR12, [r0, #MMX_WR12]
-	wldrd	wR13, [r0, #MMX_WR13]
-	wldrd	wR14, [r0, #MMX_WR14]
-	wldrd	wR15, [r0, #MMX_WR15]
+	wldrd	wR0,  r0, MMX_WR0
+	wldrd	wR1,  r0, MMX_WR1
+	wldrd	wR2,  r0, MMX_WR2
+	wldrd	wR3,  r0, MMX_WR3
+	wldrd	wR4,  r0, MMX_WR4
+	wldrd	wR5,  r0, MMX_WR5
+	wldrd	wR6,  r0, MMX_WR6
+	wldrd	wR7,  r0, MMX_WR7
+	wldrd	wR8,  r0, MMX_WR8
+	wldrd	wR9,  r0, MMX_WR9
+	wldrd	wR10, r0, MMX_WR10
+	wldrd	wR11, r0, MMX_WR11
+	wldrd	wR12, r0, MMX_WR12
+	wldrd	wR13, r0, MMX_WR13
+	wldrd	wR14, r0, MMX_WR14
+	wldrd	wR15, r0, MMX_WR15
 
 	@ Load wCx
-	wldrw	wCSSF, [r0, #MMX_WCSSF]
-	wldrw	wCASF, [r0, #MMX_WCASF]
-	wldrw	wCGR0, [r0, #MMX_WCGR0]
-	wldrw	wCGR1, [r0, #MMX_WCGR1]
-	wldrw	wCGR2, [r0, #MMX_WCGR2]
-	wldrw	wCGR3, [r0, #MMX_WCGR3]
+	wldrw	wCSSF, r0, MMX_WCSSF
+	wldrw	wCASF, r0, MMX_WCASF
+	wldrw	wCGR0, r0, MMX_WCGR0
+	wldrw	wCGR1, r0, MMX_WCGR1
+	wldrw	wCGR2, r0, MMX_WCGR2
+	wldrw	wCGR3, r0, MMX_WCGR3
 
 	@ clear CUP/MUP (only if r1 != 0)
 	teq	r1, #0
diff --git a/arch/arm/kernel/iwmmxt.h b/arch/arm/kernel/iwmmxt.h
new file mode 100644
index 000000000000..fb627286f5bb
--- /dev/null
+++ b/arch/arm/kernel/iwmmxt.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __IWMMXT_H__
+#define __IWMMXT_H__
+
+.irp b, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
+.set .LwR\b, \b
+.set .Lr\b, \b
+.endr
+
+.set .LwCSSF, 0x2
+.set .LwCASF, 0x3
+.set .LwCGR0, 0x8
+.set .LwCGR1, 0x9
+.set .LwCGR2, 0xa
+.set .LwCGR3, 0xb
+
+.macro wldrd, reg:req, base:req, offset:req
+.inst 0xedd00100 | (.L\reg << 12) | (.L\base << 16) | (\offset >> 2)
+.endm
+
+.macro wldrw, reg:req, base:req, offset:req
+.inst 0xfd900100 | (.L\reg << 12) | (.L\base << 16) | (\offset >> 2)
+.endm
+
+.macro wstrd, reg:req, base:req, offset:req
+.inst 0xedc00100 | (.L\reg << 12) | (.L\base << 16) | (\offset >> 2)
+.endm
+
+.macro wstrw, reg:req, base:req, offset:req
+.inst 0xfd800100 | (.L\reg << 12) | (.L\base << 16) | (\offset >> 2)
+.endm
+
+#ifdef __clang__
+
+#define wCon c1
+
+.macro tmrc, dest:req, control:req
+mrc p1, 0, \dest, \control, c0, 0
+.endm
+
+.macro tmcr, control:req, src:req
+mcr p1, 0, \src, \control, c0, 0
+.endm
+#endif
+
+#endif
-- 
2.29.2.299.gdc1121823c-goog