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cmd/compile: fix PrefetchStreamed builtin implementation on PPC64

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This CL fixes encoding of PrefetchStreamed on PPC64 to be consistent
with what is implemented on AMD64 and ARM64 platforms which is
prefetchNTA (prefetch non-temporal access). Looking at the definition
of prefetchNTA, the closest corresponding Touch hint (TH) value to be
used on PPC64 is 16 that states that the address is accessed in a
transient manner. Current usage of TH=8 may cause degraded
performance.

Change-Id: I393bf5a9b971a22f632b3cbfb4fa659062af9a27
Reviewed-on: https://go-review.googlesource.com/c/go/+/390316
Reviewed-by: Paul Murphy <murp@ibm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Archana R 2022-03-07 01:54:14 -06:00 committed by Paul Murphy
parent e475cf2e70
commit 7b15e297a2
2 changed files with 8 additions and 4 deletions
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8
src/cmd/compile/internal/ssa/gen/PPC64.rules
View File

@ -1479,7 +1479,11 @@
&& clobber(call)
=> (Move [sz] dst src mem)
// Prefetch instructions (aux is option: 0 - DCBT ; 8 - DCBT stream)
// Prefetch instructions (TH specified using aux field)
// For DCBT Ra,Rb,TH, A value of TH indicates:
// 0, hint this cache line will be used soon. (PrefetchCache)
// 16, hint this cache line will not be used for long. (PrefetchCacheStreamed)
// See ISA 3.0 Book II 4.3.2 for more detail. https://openpower.foundation/specifications/isa/
(PrefetchCache ptr mem) => (DCBT ptr mem [0])
(PrefetchCacheStreamed ptr mem) => (DCBT ptr mem [8])
(PrefetchCacheStreamed ptr mem) => (DCBT ptr mem [16])

4
src/cmd/compile/internal/ssa/rewritePPC64.go
View File

@ -14140,12 +14140,12 @@ func rewriteValuePPC64_OpPrefetchCacheStreamed(v *Value) bool {
v_1 := v.Args[1]
v_0 := v.Args[0]
// match: (PrefetchCacheStreamed ptr mem)
// result: (DCBT ptr mem [8])
// result: (DCBT ptr mem [16])
for {
ptr := v_0
mem := v_1
v.reset(OpPPC64DCBT)
v.AuxInt = int64ToAuxInt(8)
v.AuxInt = int64ToAuxInt(16)
v.AddArg2(ptr, mem)
return true
}