OpenJDK / jdk / jdk
changeset 52105:537dbfcef4a7
8211046: Forced data dependencies serve no purpose on x86
Reviewed-by: eosterlund, rehn
| author | dholmes |
|---|---|
| date | Fri, 12 Oct 2018 03:51:02 -0400 |
| parents | 331fbd2db6b5 |
| children | 76d526565453 |
| files | src/hotspot/cpu/x86/jniFastGetField_x86_64.cpp |
| diffstat | 1 files changed, 2 insertions(+), 27 deletions(-) [+] |
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--- a/src/hotspot/cpu/x86/jniFastGetField_x86_64.cpp Fri Oct 12 12:37:13 2018 +0530 +++ b/src/hotspot/cpu/x86/jniFastGetField_x86_64.cpp Fri Oct 12 03:51:02 2018 -0400 @@ -35,9 +35,6 @@ #define BUFFER_SIZE 30*wordSize -// Instead of issuing lfence for LoadLoad barrier, we create data dependency -// between loads, which is more efficient than lfence. - // Common register usage: // rax/xmm0: result // c_rarg0: jni env @@ -77,12 +74,6 @@ __ mov (robj, c_rarg1); __ testb (rcounter, 1); __ jcc (Assembler::notZero, slow); - - __ xorptr(robj, rcounter); - __ xorptr(robj, rcounter); // obj, since - // robj ^ rcounter ^ rcounter == robj - // robj is data dependent on rcounter. - __ mov (roffset, c_rarg2); __ shrptr(roffset, 2); // offset @@ -103,12 +94,7 @@ default: ShouldNotReachHere(); } - // create data dependency on rax - __ lea(rcounter_addr, counter); - __ xorptr(rcounter_addr, rax); - __ xorptr(rcounter_addr, rax); - __ cmpl (rcounter, Address(rcounter_addr, 0)); - + __ cmp32 (rcounter, counter); __ jcc (Assembler::notEqual, slow); __ ret (0); @@ -178,11 +164,6 @@ __ testb (rcounter, 1); __ jcc (Assembler::notZero, slow); - __ xorptr(robj, rcounter); - __ xorptr(robj, rcounter); // obj, since - // robj ^ rcounter ^ rcounter == robj - // robj is data dependent on rcounter. - // Both robj and rtmp are clobbered by try_resolve_jobject_in_native. BarrierSetAssembler* bs = BarrierSet::barrier_set()->barrier_set_assembler(); bs->try_resolve_jobject_in_native(masm, /* jni_env */ c_rarg0, robj, rtmp, slow); @@ -198,13 +179,7 @@ case T_DOUBLE: __ movdbl (xmm0, Address(robj, roffset, Address::times_1)); break; default: ShouldNotReachHere(); } - - __ lea(rcounter_addr, counter); - __ movdq (rax, xmm0); - // counter address is data dependent on xmm0. - __ xorptr(rcounter_addr, rax); - __ xorptr(rcounter_addr, rax); - __ cmpl (rcounter, Address(rcounter_addr, 0)); + __ cmp32 (rcounter, counter); __ jcc (Assembler::notEqual, slow); __ ret (0);