[newlib-cygwin/main] amdgcn, libm: fix vector ilogb bugs (bug 33272)
Jeff Johnston
jjohnstn@sourceware.org
Wed Aug 27 21:46:04 GMT 2025
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=bd409f3c12e28e1464dec7fd0d45db30280f1e56
commit bd409f3c12e28e1464dec7fd0d45db30280f1e56
Author: Andrew Stubbs <ams@baylibre.com>
Date: Wed Aug 27 10:11:25 2025 +0000
amdgcn, libm: fix vector ilogb bugs (bug 33272)
The vector ilogb routines, including the ones inlined into fmod, had a bug
in which the conditional masks were not properly applied, causing the value of
one lane to be affected by conditional choices of another lane. The problem
was not immediately obviously because all values were calculated correctly when
no lane contained a subnormal input.
The problem is fixed by proper use of VECTOR_COND_MOVE and VECTOR_WHILE.
Diff:
---
newlib/libm/machine/amdgcn/amdgcn_veclib.h | 10 +++-
newlib/libm/machine/amdgcn/v64df_fmod.c | 95 +++++++++++++++---------------
newlib/libm/machine/amdgcn/v64df_ilogb.c | 22 +++----
newlib/libm/machine/amdgcn/v64sf_fmod.c | 58 ++++++++----------
newlib/libm/machine/amdgcn/v64sf_ilogb.c | 11 ++--
5 files changed, 99 insertions(+), 97 deletions(-)
diff --git a/newlib/libm/machine/amdgcn/amdgcn_veclib.h b/newlib/libm/machine/amdgcn/amdgcn_veclib.h
index 9e9d3ebf0..f7dadb7e4 100644
--- a/newlib/libm/machine/amdgcn/amdgcn_veclib.h
+++ b/newlib/libm/machine/amdgcn/amdgcn_veclib.h
@@ -267,7 +267,15 @@ do { \
__tmp; \
})
-#define VECTOR_WHILE(cond, cond_var, prev_cond_var) \
+#define VECTOR_WHILE(cond, cond_var) \
+{ \
+ __auto_type cond_var = __mask; \
+ for (;;) { \
+ cond_var &= __builtin_convertvector (cond, __typeof (cond_var)); \
+ if (ALL_ZEROES_P (cond_var)) \
+ break;
+
+#define VECTOR_WHILE2(cond, cond_var, prev_cond_var) \
{ \
__auto_type cond_var = prev_cond_var; \
for (;;) { \
diff --git a/newlib/libm/machine/amdgcn/v64df_fmod.c b/newlib/libm/machine/amdgcn/v64df_fmod.c
index 750546f60..ba12577b1 100644
--- a/newlib/libm/machine/amdgcn/v64df_fmod.c
+++ b/newlib/libm/machine/amdgcn/v64df_fmod.c
@@ -61,17 +61,19 @@ DEF_VD_MATH_FUNC (v64df, fmod, v64df x, v64df y)
v64si ix;
VECTOR_IF (hx < 0x00100000, cond) // subnormal x
VECTOR_IF2 (hx == 0, cond2, cond)
- ix = VECTOR_INIT (-1043);
- for (v64si i = __builtin_convertvector (lx, v64si);
- !ALL_ZEROES_P (cond2 & (i > 0));
- i <<= 1)
- VECTOR_COND_MOVE (ix, ix - 1, cond2 & (i > 0));
+ VECTOR_COND_MOVE (ix, VECTOR_INIT (-1043), cond2);
+ v64si i = __builtin_convertvector (lx, v64si);
+ VECTOR_WHILE2 (i > 0, cond3, cond2);
+ VECTOR_COND_MOVE (ix, ix - 1, cond3);
+ VECTOR_COND_MOVE (i, i << 1, cond3);
+ VECTOR_ENDWHILE
VECTOR_ELSE2 (cond2, cond)
- ix = VECTOR_INIT (-1022);
- for (v64si i = __builtin_convertvector (hx << 11, v64si);
- !ALL_ZEROES_P (cond2 & (i > 0));
- i <<= 1)
- VECTOR_COND_MOVE (ix, ix - 1, cond2 & (i > 0));
+ VECTOR_COND_MOVE (ix, VECTOR_INIT (-1022), cond2);
+ v64si i = __builtin_convertvector (hx << 11, v64si);
+ VECTOR_WHILE2 (i > 0, cond3, cond2)
+ VECTOR_COND_MOVE (ix, ix - 1, cond3);
+ VECTOR_COND_MOVE (i, i << 1, cond3);
+ VECTOR_ENDWHILE
VECTOR_ENDIF
VECTOR_ELSE (cond)
VECTOR_COND_MOVE (ix, (hx >> 20) - 1023, cond);
@@ -81,17 +83,19 @@ DEF_VD_MATH_FUNC (v64df, fmod, v64df x, v64df y)
v64si iy;
VECTOR_IF (hy < 0x00100000, cond) // subnormal y
VECTOR_IF2 (hy == 0, cond2, cond)
- iy = VECTOR_INIT (-1043);
- for (v64si i = __builtin_convertvector (ly, v64si);
- !ALL_ZEROES_P (cond2 & (i > 0));
- i <<= 1)
- VECTOR_COND_MOVE (iy, iy - 1, cond2 & (i > 0));
+ VECTOR_COND_MOVE (iy, VECTOR_INIT (-1043), cond2);
+ v64si i = __builtin_convertvector (ly, v64si);
+ VECTOR_WHILE2 (i > 0, cond3, cond2);
+ VECTOR_COND_MOVE (iy, iy - 1, cond3);
+ VECTOR_COND_MOVE (i, i << 1, cond3);
+ VECTOR_ENDWHILE
VECTOR_ELSE2 (cond2, cond)
- iy = VECTOR_INIT (-1022);
- for (v64si i = __builtin_convertvector (hy << 11, v64si);
- !ALL_ZEROES_P (cond2 & (i > 0));
- i <<= 1)
- VECTOR_COND_MOVE (iy, iy - 1, cond2 & (i > 0));
+ VECTOR_COND_MOVE (iy, VECTOR_INIT (-1022), cond2);
+ v64si i = __builtin_convertvector (hy << 11, v64si);
+ VECTOR_WHILE2 (i > 0, cond3, cond2);
+ VECTOR_COND_MOVE (iy, iy - 1, cond3);
+ VECTOR_COND_MOVE (i, i << 1, cond3);
+ VECTOR_ENDWHILE
VECTOR_ENDIF
VECTOR_ELSE (cond)
VECTOR_COND_MOVE (iy, (hy >> 20) - 1023, cond);
@@ -130,29 +134,26 @@ DEF_VD_MATH_FUNC (v64df, fmod, v64df x, v64df y)
/* fix point fmod */
v64si n = ix - iy;
- v64si cond = n != 0;
- while (!ALL_ZEROES_P (cond))
- {
- hz = hx - hy;
- lz = lx - ly;
- VECTOR_IF2 (lx < ly, cond2, cond)
- VECTOR_COND_MOVE (hz, hz - 1, cond2);
- VECTOR_ENDIF
- VECTOR_IF2 (hz < 0, cond2, cond)
- VECTOR_COND_MOVE (hx, hx + hx + (__builtin_convertvector(lx, v64usi) >> 31), cond2);
- VECTOR_COND_MOVE (lx, lx + lx, cond2);
- VECTOR_ELSE2 (cond2, cond)
- VECTOR_IF2 ((hz | lz) == 0, cond3, cond2) // return sign(x)*0
- VECTOR_RETURN (zeroes, cond3);
- VECTOR_ENDIF
- VECTOR_COND_MOVE (hx, hz + hz + (__builtin_convertvector(lz, v64usi) >> 31), cond2);
- VECTOR_COND_MOVE (lx, lz + lz, cond2);
+ VECTOR_WHILE (n != 0, cond)
+ hz = hx - hy;
+ lz = lx - ly;
+ VECTOR_IF2 (lx < ly, cond2, cond)
+ VECTOR_COND_MOVE (hz, hz - 1, cond2);
+ VECTOR_ENDIF
+ VECTOR_IF2 (hz < 0, cond2, cond)
+ VECTOR_COND_MOVE (hx, hx + hx + (__builtin_convertvector(lx, v64usi) >> 31), cond2);
+ VECTOR_COND_MOVE (lx, lx + lx, cond2);
+ VECTOR_ELSE2 (cond2, cond)
+ VECTOR_IF2 ((hz | lz) == 0, cond3, cond2) // return sign(x)*0
+ VECTOR_RETURN (zeroes, cond3);
VECTOR_ENDIF
+ VECTOR_COND_MOVE (hx, hz + hz + (__builtin_convertvector(lz, v64usi) >> 31), cond2);
+ VECTOR_COND_MOVE (lx, lz + lz, cond2);
+ VECTOR_ENDIF
- n += cond; // Active lanes should be -1
- cond &= (n != 0);
- }
+ VECTOR_COND_MOVE (n, n - 1, cond);
+ VECTOR_ENDWHILE
hz = hx - hy;
lz = lx - ly;
@@ -164,15 +165,11 @@ DEF_VD_MATH_FUNC (v64df, fmod, v64df x, v64df y)
/* convert back to floating value and restore the sign */
VECTOR_RETURN (zeroes, (hx | lx) == 0); // return sign(x)*0
- cond = hx < 0x00100000;
- while (!ALL_ZEROES_P (cond)) // normalize x
- {
- VECTOR_COND_MOVE (hx, hx + hx + (lx >> 31), cond);
- VECTOR_COND_MOVE (lx, lx + lx, cond);
- iy += cond; // Active lanes should be -1
-
- cond &= (hx < 0x00100000);
- }
+ VECTOR_WHILE (hx < 0x00100000, cond) // normalize x
+ VECTOR_COND_MOVE (hx, hx + hx + (lx >> 31), cond);
+ VECTOR_COND_MOVE (lx, lx + lx, cond);
+ VECTOR_COND_MOVE (iy, iy - 1, cond);
+ VECTOR_ENDWHILE
VECTOR_IF (iy >= -1022, cond) // normalize output
VECTOR_COND_MOVE (hx, (hx - 0x00100000) | ((iy + 1023) << 20), cond);
INSERT_WORDS (x, hx | sx, lx, cond);
diff --git a/newlib/libm/machine/amdgcn/v64df_ilogb.c b/newlib/libm/machine/amdgcn/v64df_ilogb.c
index 56eb70089..5e9932297 100644
--- a/newlib/libm/machine/amdgcn/v64df_ilogb.c
+++ b/newlib/libm/machine/amdgcn/v64df_ilogb.c
@@ -36,17 +36,19 @@ DEF_VD_MATH_PRED (v64si, ilogb, v64df x)
VECTOR_IF (hx < 0x00100000, cond)
VECTOR_RETURN (VECTOR_INIT (-__INT_MAX__), cond & ((hx | lx) == 0)); // FP_ILOGB0
VECTOR_IF2 (hx == 0, cond2, cond)
- ix = VECTOR_INIT (-1043);
- for (v64si i = lx;
- !ALL_ZEROES_P (cond2 & (i > 0));
- i <<= 1)
- VECTOR_COND_MOVE (ix, ix - 1, cond2 & (i > 0));
+ VECTOR_COND_MOVE (ix, VECTOR_INIT (-1043), cond2);
+ v64si i = lx;
+ VECTOR_WHILE2 (i > 0, cond3, cond2)
+ VECTOR_COND_MOVE (ix, ix - 1, cond3);
+ VECTOR_COND_MOVE (i, i << 1, cond3);
+ VECTOR_ENDWHILE
VECTOR_ELSE2 (cond2, cond)
- ix = VECTOR_INIT (-1022);
- for (v64si i = (hx << 11);
- !ALL_ZEROES_P (cond2 & (i > 0));
- i <<= 1)
- VECTOR_COND_MOVE (ix, ix - 1, cond2 & (i > 0));
+ VECTOR_COND_MOVE (ix, VECTOR_INIT (-1022), cond2);
+ v64si i = (hx << 11);
+ VECTOR_WHILE2 (i > 0, cond3, cond2)
+ VECTOR_COND_MOVE (ix, ix - 1, cond3);
+ VECTOR_COND_MOVE (i, i << 1, cond3);
+ VECTOR_ENDWHILE
VECTOR_ENDIF
VECTOR_RETURN (ix, cond);
VECTOR_ENDIF
diff --git a/newlib/libm/machine/amdgcn/v64sf_fmod.c b/newlib/libm/machine/amdgcn/v64sf_fmod.c
index b62b81929..e4ddfc299 100644
--- a/newlib/libm/machine/amdgcn/v64sf_fmod.c
+++ b/newlib/libm/machine/amdgcn/v64sf_fmod.c
@@ -57,11 +57,12 @@ DEF_VS_MATH_FUNC (v64sf, fmodf, v64sf x, v64sf y)
/* determine ix = ilogb(x) */
v64si ix;
VECTOR_IF (hx < 0x00800000, cond) // subnormal x
- ix = VECTOR_INIT (-126);
- for (v64si i = (hx << 8);
- !ALL_ZEROES_P (cond & (i > 0));
- i <<= 1)
- VECTOR_COND_MOVE (ix, ix - 1, cond & (i > 0));
+ VECTOR_COND_MOVE (ix, VECTOR_INIT (-126), cond);
+ v64si i = hx << 8;
+ VECTOR_WHILE2 (i > 0, cond2, cond)
+ VECTOR_COND_MOVE (ix, ix - 1, cond2);
+ VECTOR_COND_MOVE (i, i << 1, cond2);
+ VECTOR_ENDWHILE
VECTOR_ELSE (cond)
VECTOR_COND_MOVE (ix, (hx >> 23) - 127, cond);
VECTOR_ENDIF
@@ -69,12 +70,12 @@ DEF_VS_MATH_FUNC (v64sf, fmodf, v64sf x, v64sf y)
/* determine iy = ilogb(y) */
v64si iy;
VECTOR_IF (hy < 0x00800000, cond) // subnormal y
- iy = VECTOR_INIT (-126);
- for (v64si i = (hy << 8); !ALL_ZEROES_P (cond & (i >= 0)); /* i <<= 1 */)
- {
- VECTOR_COND_MOVE (iy, iy - 1, cond & (i >= 0));
- VECTOR_COND_MOVE (i, i << 1, cond & (i >= 0));
- }
+ VECTOR_COND_MOVE (iy, VECTOR_INIT (-126), cond);
+ v64si i = (hy << 8);
+ VECTOR_WHILE2 (i >= 0, cond2, cond)
+ VECTOR_COND_MOVE (iy, iy - 1, cond2);
+ VECTOR_COND_MOVE (i, i << 1, cond2);
+ VECTOR_ENDWHILE
VECTOR_ELSE (cond)
VECTOR_COND_MOVE (iy, (hy >> 23) - 127, cond);
VECTOR_ENDIF
@@ -99,24 +100,21 @@ DEF_VS_MATH_FUNC (v64sf, fmodf, v64sf x, v64sf y)
/* fix point fmod */
v64si n = ix - iy;
- v64si cond = n != 0;
- while (!ALL_ZEROES_P (cond))
- {
- hz = hx - hy;
- VECTOR_IF2 (hz < 0, cond2, cond)
- VECTOR_COND_MOVE (hx, hx + hx, cond2);
- VECTOR_ELSE2 (cond2, cond)
- VECTOR_IF2 (hz == 0, cond3, cond2) // return sign(x)*0
- VECTOR_RETURN (zeroes, cond3);
- VECTOR_ELSE2 (cond3, cond2)
- VECTOR_COND_MOVE (hx, hz + hz, cond2);
- VECTOR_ENDIF
+ VECTOR_WHILE (n != 0, cond)
+ hz = hx - hy;
+ VECTOR_IF2 (hz < 0, cond2, cond)
+ VECTOR_COND_MOVE (hx, hx + hx, cond2);
+ VECTOR_ELSE2 (cond2, cond)
+ VECTOR_IF2 (hz == 0, cond3, cond2) // return sign(x)*0
+ VECTOR_RETURN (zeroes, cond3);
+ VECTOR_ELSE2 (cond3, cond2)
+ VECTOR_COND_MOVE (hx, hz + hz, cond2);
VECTOR_ENDIF
+ VECTOR_ENDIF
- n += cond; // Active lanes should be -1
- cond &= (n != 0);
- }
+ n += cond; // Active lanes should be -1
+ VECTOR_ENDWHILE
hz = hx - hy;
VECTOR_COND_MOVE (hx, hz, hz >= 0);
@@ -124,14 +122,10 @@ DEF_VS_MATH_FUNC (v64sf, fmodf, v64sf x, v64sf y)
/* convert back to floating value and restore the sign */
VECTOR_RETURN (zeroes, hx == 0); // return sign(x)*0
- cond = hx < 0x00800000;
- while (!ALL_ZEROES_P (cond)) // normalize x
- {
+ VECTOR_WHILE (hx < 0x00800000, cond) // normalize x
VECTOR_COND_MOVE (hx, hx + hx, cond);
iy += cond; // Active lanes should be -1
-
- cond &= (hx < 0x00800000);
- }
+ VECTOR_ENDWHILE
VECTOR_IF (iy >= -126, cond) // normalize output
VECTOR_COND_MOVE (hx, (hx - 0x00800000) | ((iy + 127) << 23), cond);
SET_FLOAT_WORD (x, hx | sx, cond);
diff --git a/newlib/libm/machine/amdgcn/v64sf_ilogb.c b/newlib/libm/machine/amdgcn/v64sf_ilogb.c
index 2f2a7cac7..ecaf99653 100644
--- a/newlib/libm/machine/amdgcn/v64sf_ilogb.c
+++ b/newlib/libm/machine/amdgcn/v64sf_ilogb.c
@@ -38,11 +38,12 @@ DEF_VS_MATH_FUNC (v64si, ilogbf, v64sf x)
VECTOR_RETURN (VECTOR_INIT (-__INT_MAX__), cond); // FP_ILOGB0
VECTOR_ENDIF
VECTOR_IF (FLT_UWORD_IS_SUBNORMAL (hx), cond)
- ix = VECTOR_INIT (-126);
- for (v64si i = (hx << 8);
- !ALL_ZEROES_P (cond & (i > 0));
- i <<= 1)
- VECTOR_COND_MOVE (ix, ix - 1, cond & (i > 0));
+ VECTOR_COND_MOVE (ix, VECTOR_INIT (-126), cond);
+ v64si i = (hx << 8);
+ VECTOR_WHILE2 (i > 0, cond2, cond)
+ VECTOR_COND_MOVE (ix, ix - 1, cond2);
+ VECTOR_COND_MOVE (i, i << 1, cond2);
+ VECTOR_ENDWHILE
VECTOR_RETURN (ix, cond);
VECTOR_ELSEIF (~FLT_UWORD_IS_FINITE (hx), cond)
VECTOR_RETURN (VECTOR_INIT (__INT_MAX__), cond);
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