[x86/SLH] Teach speculative load hardening to correctly harden the
indices used by AVX2 and AVX-512 gather instructions.
The index vector is hardened by broadcasting the predicate state
into a vector register and then or-ing. We don't even have to worry
about EFLAGS here.
I've added a test for all of the gather intrinsics to make sure that we
don't miss one. A particularly interesting creation is the gather
prefetch, which needs to be marked as potentially "loading" to get the
correct behavior. It's a memory access in many ways, and is actually
relevant for SLH. Based on discussion with Craig in review, I've moved
it to be `mayLoad` and `mayStore` rather than generic side effects. This
matches how we model other prefetch instructions.
Many thanks to Craig for the review here.
Differential Revision: https://reviews.llvm.org/D49336
llvm-svn: 337144
diff --git a/llvm/lib/Target/X86/X86InstrAVX512.td b/llvm/lib/Target/X86/X86InstrAVX512.td
index c778b48..36c859a 100644
--- a/llvm/lib/Target/X86/X86InstrAVX512.td
+++ b/llvm/lib/Target/X86/X86InstrAVX512.td
@@ -9588,7 +9588,7 @@
// prefetch
multiclass avx512_gather_scatter_prefetch<bits<8> opc, Format F, string OpcodeStr,
RegisterClass KRC, X86MemOperand memop> {
- let Predicates = [HasPFI], hasSideEffects = 1 in
+ let Predicates = [HasPFI], mayLoad = 1, mayStore = 1 in
def m : AVX5128I<opc, F, (outs), (ins KRC:$mask, memop:$src),
!strconcat(OpcodeStr, "\t{$src {${mask}}|{${mask}}, $src}"), []>,
EVEX, EVEX_K, Sched<[WriteLoad]>;