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Restrict use of r7 in Thumb 1 code

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Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2023-05-25 11:01:41 +01:00
parent cee166e3f5
commit b047bf64e2
1 changed files with 39 additions and 20 deletions
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59
library/bn_mul.h
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@ -662,20 +662,11 @@
* There is a fairly complex matrix of supported options for Thumb / Thumb2 / Arm
* assembly. Choosing the correct codepath depends on the target, the compiler,
* and the optimisation level.
*
* Note, gcc -O0 by default uses r7 for the frame pointer, so it complains about
* our use of r7 below, unless -fomit-frame-pointer is passed.
*
* On the other hand, -fomit-frame-pointer is implied by any -Ox options with
* x !=0, which we can detect using __OPTIMIZE__ (which is also defined by
* clang and armcc5 under the same conditions).
*/
#if defined(__thumb__) && !defined(__thumb2__) // Thumb 1 (not Thumb 2) ISA
// Only supported by gcc, when optimisation is enabled; only Thumb 1 codepath works
#if defined(__OPTIMIZE__) && defined(__GNUC__)
#define ARM_THUMB_1
#endif
#elif defined(__thumb2__) // Thumb 2 ISA
@ -702,21 +693,48 @@
#if defined(ARM_THUMB_1)
#if defined(__OPTIMIZE__) && defined(__GNUC__)
/*
* Note, gcc -O0 by default uses r7 for the frame pointer, so it complains about
* our use of r7 below, unless -fomit-frame-pointer is passed.
*
* On the other hand, -fomit-frame-pointer is implied by any -Ox options with
* x !=0, which we can detect using __OPTIMIZE__ (which is also defined by
* clang and armcc5 under the same conditions).
*
* If gcc needs to use r7, we use r1 as a scratch register and have a few extra
* instructions to preserve/restore it; otherwise, we can use r7 and avoid
* the preserve/restore overhead.
*/
#define MULADDC_SCRATCH "RS .req r1 \n\t"
#define MULADDC_PRESERVE_R1 "mov r10, r1 \n\t"
#define MULADDC_RESTORE_R1 "mov r1, r10 \n\t"
#define MULADDC_SCRATCH_CLOBBER "r10"
#else
#define MULADDC_SCRATCH "RS .req r7 \n\t"
#define MULADDC_PRESERVE_R1 ""
#define MULADDC_RESTORE_R1 ""
#define MULADDC_SCRATCH_CLOBBER "r7"
#endif
#define MULADDC_X1_INIT \
asm( \
MULADDC_SCRATCH \
"ldr r0, %3 \n\t" \
"ldr r1, %4 \n\t" \
"ldr r2, %5 \n\t" \
"ldr r3, %6 \n\t" \
"lsr r7, r3, #16 \n\t" \
"mov r9, r7 \n\t" \
"lsl r7, r3, #16 \n\t" \
"lsr r7, r7, #16 \n\t" \
"mov r8, r7 \n\t"
"lsr r4, r3, #16 \n\t" \
"mov r9, r4 \n\t" \
"lsl r4, r3, #16 \n\t" \
"lsr r4, r4, #16 \n\t" \
"mov r8, r4 \n\t" \
#define MULADDC_X1_CORE \
MULADDC_PRESERVE_R1 \
"ldmia r0!, {r6} \n\t" \
"lsr r7, r6, #16 \n\t" \
"lsr RS, r6, #16 \n\t" \
"lsl r6, r6, #16 \n\t" \
"lsr r6, r6, #16 \n\t" \
"mov r4, r8 \n\t" \
@ -724,12 +742,12 @@
"mov r3, r9 \n\t" \
"mul r6, r3 \n\t" \
"mov r5, r9 \n\t" \
"mul r5, r7 \n\t" \
"mul r5, RS \n\t" \
"mov r3, r8 \n\t" \
"mul r7, r3 \n\t" \
"mul RS, r3 \n\t" \
"lsr r3, r6, #16 \n\t" \
"add r5, r5, r3 \n\t" \
"lsr r3, r7, #16 \n\t" \
"lsr r3, RS, #16 \n\t" \
"add r5, r5, r3 \n\t" \
"add r4, r4, r2 \n\t" \
"mov r2, #0 \n\t" \
@ -737,9 +755,10 @@
"lsl r3, r6, #16 \n\t" \
"add r4, r4, r3 \n\t" \
"adc r5, r2 \n\t" \
"lsl r3, r7, #16 \n\t" \
"lsl r3, RS, #16 \n\t" \
"add r4, r4, r3 \n\t" \
"adc r5, r2 \n\t" \
MULADDC_RESTORE_R1 \
"ldr r3, [r1] \n\t" \
"add r4, r4, r3 \n\t" \
"adc r2, r5 \n\t" \
@ -752,7 +771,7 @@
: "=m" (c), "=m" (d), "=m" (s) \
: "m" (s), "m" (d), "m" (c), "m" (b) \
: "r0", "r1", "r2", "r3", "r4", "r5", \
"r6", "r7", "r8", "r9", "cc" \
"r6", MULADDC_SCRATCH_CLOBBER, "r8", "r9", "cc" \
);
#elif defined(ARM_V6_DSP)