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[OpenMP][libomp] Fix register constraint for tpause and umwait 

Register constraint switched to "=q" which means very specifically (from
https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html#Machine-Constraints)

> Any register accessible as rl. In 32-bit mode, a, b, c, and d; in 64-bit
mode, any integer register.

Older gcc versions (8.x and below) were trying to use esi or edi for the
8 bit flag variable, but it wound up displaying this error in the end:

kmp_lock.cpp: In function ‘void __kmp_spin_backoff(kmp_backoff_t*)’:
kmp_lock.cpp:2684:1: error: unsupported size for integer register
Hence the correct restriction is "=q" instead of "=r".

Fixes: https://github.com/llvm/llvm-project/issues/53309
Differential Revision: https://reviews.llvm.org/D120519
This commit is contained in:
Jonathan Peyton 2022-03-07 14:54:07 -06:00
parent 1538bd518c
commit 6564a70415
1 changed files with 8 additions and 2 deletions
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10
openmp/runtime/src/kmp.h
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@ -1334,7 +1334,10 @@ static inline int __kmp_tpause(uint32_t hint, uint64_t counter) {
char flag;
__asm__ volatile("#tpause\n.byte 0x66, 0x0F, 0xAE, 0xF1\n"
"setb %0"
: "=r"(flag)
// The "=q" restraint means any register accessible as rl
// in 32-bit mode: a, b, c, and d;
// in 64-bit mode: any integer register
: "=q"(flag)
: "a"(timeLo), "d"(timeHi), "c"(hint)
:);
return flag;
@ -1361,7 +1364,10 @@ static inline int __kmp_umwait(uint32_t hint, uint64_t counter) {
char flag;
__asm__ volatile("#umwait\n.byte 0xF2, 0x0F, 0xAE, 0xF1\n"
"setb %0"
: "=r"(flag)
// The "=q" restraint means any register accessible as rl
// in 32-bit mode: a, b, c, and d;
// in 64-bit mode: any integer register
: "=q"(flag)
: "a"(timeLo), "d"(timeHi), "c"(hint)
:);
return flag;