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Fix remaining inline asm input/output constraints and clobbers

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Mark modified inline asm operands as read-write (+r / +c) and add missing
volatile/memory clobbers so compilers and LTO do not assume modified
registers remain unchanged across asm blocks:
- HashDjb2_NEON (compare_neon64.cc): [src] "+r"(src) for post-increment ldr
- FixedDiv1_X86 (scale_gcc.cc): "+c"(div) for sub $0x1, %1
- P410ToARGBRow_SVE_SC & P410ToAR30Row_SVE_SC (row_sve.h): [vl] "+r"(vl)
  for tail cntw %x[vl]
- SwapUVRow_RVV & ARGBMultiplyRow_RVV (row_rvv.cc): use asm volatile and
  "memory" clobber instead of VLA memory operands on mutated pointers

R=rrwinterton@gmail.com

Bug: b/571179207
Test: libyuv_unittest
Change-Id: I3c2475d1e5bdab13e74643a028eebc350edcc1bb
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/8565646
Reviewed-by: richard winterton <rrwinterton@gmail.com>
Commit-Queue: Frank Barchard <fbarchard@google.com>
This commit is contained in:
Frank Barchard 2026-10-12 19:27:07 -07:00 committed by libyuv-scoped@luci-project-accounts.iam.gserviceaccount.com
parent b9d572cc63
commit 58d817ed81
4 changed files with 24 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
include/libyuv/row_sve.h
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@ -1767,9 +1767,9 @@ static inline void P410ToARGBRow_SVE_SC(const uint16_t* src_y,
: [src_y] "+r"(src_y), // %[src_y] : [src_y] "+r"(src_y), // %[src_y]
[src_uv] "+r"(src_uv), // %[src_uv] [src_uv] "+r"(src_uv), // %[src_uv]
[dst_argb] "+r"(dst_argb), // %[dst_argb] [dst_argb] "+r"(dst_argb), // %[dst_argb]
[width] "+r"(width) // %[width] [width] "+r"(width), // %[width]
: [vl] "r"(vl), // %[vl] [vl] "+r"(vl) // %[vl]
[kUVCoeff] "r"(&yuvconstants->kUVCoeff), // %[kUVCoeff] : [kUVCoeff] "r"(&yuvconstants->kUVCoeff), // %[kUVCoeff]
[kRGBCoeffBias] "r"(&yuvconstants->kRGBCoeffBias), // %[kRGBCoeffBias] [kRGBCoeffBias] "r"(&yuvconstants->kRGBCoeffBias), // %[kRGBCoeffBias]
[width_last_y] "r"(width_last_y) // %[width_last_y] [width_last_y] "r"(width_last_y) // %[width_last_y]
: "cc", "memory", YUVTORGB_SVE_REGS); : "cc", "memory", YUVTORGB_SVE_REGS);
@ -1818,9 +1818,9 @@ static inline void P410ToAR30Row_SVE_SC(const uint16_t* src_y,
: [src_y] "+r"(src_y), // %[src_y] : [src_y] "+r"(src_y), // %[src_y]
[src_uv] "+r"(src_uv), // %[src_uv] [src_uv] "+r"(src_uv), // %[src_uv]
[dst_ar30] "+r"(dst_ar30), // %[dst_ar30] [dst_ar30] "+r"(dst_ar30), // %[dst_ar30]
[width] "+r"(width) // %[width] [width] "+r"(width), // %[width]
: [vl] "r"(vl), // %[vl] [vl] "+r"(vl) // %[vl]
[kUVCoeff] "r"(&yuvconstants->kUVCoeff), // %[kUVCoeff] : [kUVCoeff] "r"(&yuvconstants->kUVCoeff), // %[kUVCoeff]
[kRGBCoeffBias] "r"(&yuvconstants->kRGBCoeffBias), // %[kRGBCoeffBias] [kRGBCoeffBias] "r"(&yuvconstants->kRGBCoeffBias), // %[kRGBCoeffBias]
[width_last_y] "r"(width_last_y), // %[width_last_y] [width_last_y] "r"(width_last_y), // %[width_last_y]
[limit] "r"(limit) // %[limit] [limit] "r"(limit) // %[limit]

6
source/compare_neon64.cc
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@ -145,12 +145,12 @@ uint32_t HashDjb2_NEON(const uint8_t* src, int count, uint32_t seed) {
"add %w[tmp], %w[tmp], %w[tmp2] \n" "add %w[tmp], %w[tmp], %w[tmp2] \n"
"madd %w[hash], %w[hash], %w[c16], %w[tmp] \n" "madd %w[hash], %w[hash], %w[c16], %w[tmp] \n"
"b.gt 1b \n" "b.gt 1b \n"
: [hash] "+r"(hash), // %[hash] : [src] "+r"(src), // %[src]
[hash] "+r"(hash), // %[hash]
[count] "+r"(count), // %[count] [count] "+r"(count), // %[count]
[tmp] "=&r"(tmp), // %[tmp] [tmp] "=&r"(tmp), // %[tmp]
[tmp2] "=&r"(tmp2) // %[tmp2] [tmp2] "=&r"(tmp2) // %[tmp2]
: [src] "r"(src), // %[src] : [kMuls] "r"(kDjb2Multiplicands), // %[kMuls]
[kMuls] "r"(kDjb2Multiplicands), // %[kMuls]
[kIdx] "r"(kDjb2WidenIndices), // %[kIdx] [kIdx] "r"(kDjb2WidenIndices), // %[kIdx]
[c16] "r"(c16) // %[c16] [c16] "r"(c16) // %[c16]
: "cc", "memory", "v0", "v1", "v2", "v3", "v4", "v5", "v6", "v7", "v16", : "cc", "memory", "v0", "v1", "v2", "v3", "v4", "v5", "v6", "v7", "v16",

30
source/row_rvv.cc
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@ -1711,10 +1711,9 @@ void MergeUVRow_RVV(const uint8_t* src_u,
#ifdef HAS_SWAPUVROW_RVV #ifdef HAS_SWAPUVROW_RVV
void SwapUVRow_RVV(const uint8_t* src_uv, uint8_t* dst_vu, int width) { void SwapUVRow_RVV(const uint8_t* src_uv, uint8_t* dst_vu, int width) {
assert(width != 0); assert(width != 0);
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wvla"
size_t vl; size_t vl;
asm("1: \n" asm volatile(
"1: \n"
"vsetvli %[vl], %[w], e16, m4, ta, ma \n" "vsetvli %[vl], %[w], e16, m4, ta, ma \n"
"vle16.v v8, (%[src_uv]) \n" "vle16.v v8, (%[src_uv]) \n"
"vsrl.vi v12, v8, 8 \n" "vsrl.vi v12, v8, 8 \n"
@ -1729,11 +1728,10 @@ void SwapUVRow_RVV(const uint8_t* src_uv, uint8_t* dst_vu, int width) {
: [src_uv] "+r"(src_uv), // %[src_uv] : [src_uv] "+r"(src_uv), // %[src_uv]
[dst_vu] "+r"(dst_vu), // %[dst_vu] [dst_vu] "+r"(dst_vu), // %[dst_vu]
[w] "+r"(width), // %[w] [w] "+r"(width), // %[w]
[vl] "=&r"(vl), // %[vl] [vl] "=&r"(vl) // %[vl]
"=m"(*(uint8_t (*)[width * 2]) dst_vu) :
: "m"(*(const uint8_t (*)[width * 2]) src_uv) : RVV_VL_CLOBBER "memory", "v8", "v9", "v10", "v11", "v12", "v13", "v14",
: RVV_VL_CLOBBER "v8", "v9", "v10", "v11", "v12", "v13", "v14", "v15"); "v15");
#pragma GCC diagnostic pop
} }
#endif #endif
@ -2330,10 +2328,9 @@ void ARGBMultiplyRow_RVV(const uint8_t* src_argb,
int width) { int width) {
assert(width != 0); assert(width != 0);
size_t w = (size_t)width * 4; size_t w = (size_t)width * 4;
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wvla"
size_t vl; size_t vl;
asm("1: \n" asm volatile(
"1: \n"
"vsetvli %[vl], %[w], e8, m2, ta, ma \n" "vsetvli %[vl], %[w], e8, m2, ta, ma \n"
"vle8.v v8, (%[src0]) \n" "vle8.v v8, (%[src0]) \n"
"vle8.v v10, (%[src1]) \n" "vle8.v v10, (%[src1]) \n"
@ -2350,13 +2347,10 @@ void ARGBMultiplyRow_RVV(const uint8_t* src_argb,
[src1] "+r"(src_argb1), // %[src1] [src1] "+r"(src_argb1), // %[src1]
[dst] "+r"(dst_argb), // %[dst] [dst] "+r"(dst_argb), // %[dst]
[w] "+r"(w), // %[w] [w] "+r"(w), // %[w]
[vl] "=&r"(vl), // %[vl] [vl] "=&r"(vl) // %[vl]
"=m"(*(uint8_t (*)[w])dst_argb) : [k128] "r"(128) // %[k128]
: [k128] "r"(128), // %[k128] : RVV_VL_CLOBBER "memory", "v8", "v9", "v10", "v11", "v12", "v13", "v14",
"m"(*(const uint8_t (*)[w])src_argb), "v15");
"m"(*(const uint8_t (*)[w])src_argb1)
: RVV_VL_CLOBBER "v8", "v9", "v10", "v11", "v12", "v13", "v14", "v15");
#pragma GCC diagnostic pop
} }
#endif #endif

5
source/scale_gcc.cc
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@ -3084,8 +3084,9 @@ int FixedDiv1_X86(int num, int div) {
"sub $0x1,%1 \n" "sub $0x1,%1 \n"
"idiv %1 \n" "idiv %1 \n"
"mov %0, %%eax \n" "mov %0, %%eax \n"
: "+a"(num) // %0 : "+a"(num), // %0
: "c"(div) // %1 "+c"(div) // %1
:
: "memory", "cc", "edx"); : "memory", "cc", "edx");
return num; return num;
} }