[go] simd/internal/spec: fix ConvertToZ width rounding
4 views
Skip to first unread message
Austin Clements (Gerrit)
Sep 5, 2026, 2:25:42 PMSep 5
to David Chase, Junyang Shao, goph...@pubsubhelper.golang.org, Austin Clements, golang-co...@googlegroups.com
Attention needed from David Chase and Junyang Shao
Austin Clements has uploaded the change for review![]( "Open in Gerrit")
Austin Clements would like David Chase and Junyang Shao to review this change.
Commit message
simd/internal/spec: fix ConvertToZ width rounding
The current "zL=xL" constraint doesn't apply width rounding, so we
don't get
(Float64x2).ConverToFloat32() Float32x4
This changes the constraint to z={zB}{zN}x{xL}, which does apply width
rounding, so we do get the width-rounded method.
Change-Id: I9248f858459aa83ec516f016e682506771ad7385
Change diff
diff --git a/src/simd/internal/spec/converts.go b/src/simd/internal/spec/converts.go
index 7f24db7..16baea7 100644
--- a/src/simd/internal/spec/converts.go
+++ b/src/simd/internal/spec/converts.go
@@ -9,7 +9,7 @@
// ConvertToZ converts element values to {zE}. The result has the same number of lanes.
//
//specgen:name ConvertTo{zE}
-//specgen:require zL=xL zE!=xE
+//specgen:require z={zB}{zN}x{xL} zE!=xE
func ConvertToZ[xE Nums, xW Width, zE Nums, zW Width](x Vec[xE, xW]) (z Vec[zE, zW]) {
// Architectures are generally significantly more constrained in what they
// will convert between, but this operation describes the full universe of
diff --git a/src/simd/internal/spec/doc.go b/src/simd/internal/spec/doc.go
index 35b8675..1f6d137 100644
--- a/src/simd/internal/spec/doc.go
+++ b/src/simd/internal/spec/doc.go
@@ -104,6 +104,16 @@
// zB=vB zN=vN*2 zL=vL/2 Constrain each component separately
// zE={vB}{vN*2} zW=vW Constrain the element type and width separately
//
+// ### Width rounding
+//
+// Some operations would naturally result in an impossible vector size. For
+// example, converting a Float64x2 vector to float32s would naturally result in
+// Float32x2, which is only 64 bits and thus smaller than the smallest vector
+// size. For operations like this, we use "width rounding".
+//
+// Width rounding is applied specifically by the vector expression form BaseNxL.
+// If NxL would be < 128, the result rounds L up to 128/N.
+//
// ## Name and doc templates
//
// For some operations, the API name or documentation depends on type
Change information
Files:
- M src/simd/internal/spec/converts.go
- M src/simd/internal/spec/doc.go
Change size: S
Delta: 2 files changed, 11 insertions(+), 1 deletion(-)
Related details
Attention is currently required from:
- David Chase
- Junyang Shao
Submit Requirements:
Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Junyang Shao (Gerrit)
Sep 9, 2026, 2:56:51 PMSep 9
to Austin Clements, goph...@pubsubhelper.golang.org, golang...@luci-project-accounts.iam.gserviceaccount.com, David Chase, golang-co...@googlegroups.com
Attention needed from Austin Clements and David Chase
Junyang Shao voted Code-Review+2![]( "Open in Gerrit")
Attention is currently required from:
- Austin Clements
- David Chase
Submit Requirements:
Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Austin Clements (Gerrit)
Sep 9, 2026, 3:56:52 PMSep 9
to Austin Clements, goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Attention needed from Austin Clements and David Chase
Austin Clements uploaded new patchset![]( "Open in Gerrit")
Austin Clements uploaded patch set #2 to this change.
Following approvals got outdated and were removed:
- TryBots-Pass: LUCI-TryBot-Result+1 by golang...@luci-project-accounts.iam.gserviceaccount.com
Related details
Attention is currently required from:
- Austin Clements
- David Chase
Submit Requirements:
Code-Review
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Gopher Robot (Gerrit)
Sep 10, 2026, 10:59:14 AMSep 10
to Austin Clements, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, golang...@luci-project-accounts.iam.gserviceaccount.com, Junyang Shao, David Chase, golang-co...@googlegroups.com
Gopher Robot submitted the change![]( "Open in Gerrit")
Unreviewed changes
1 is the latest approved patch-set.
No files were changed between the latest approved patch-set and the submitted one.
Change information
Commit message:
simd/internal/spec: fix ConvertToZ width rounding
The current "zL=xL" constraint doesn't apply width rounding, so we
don't get
(Float64x2).ConverToFloat32() Float32x4
This changes the constraint to z={zB}{zN}x{xL}, which does apply width
rounding, so we do get the width-rounded method.
Change-Id: I9248f858459aa83ec516f016e682506771ad7385
Reviewed-on: https://go-review.googlesource.com/c/go/+/828144
LUCI-TryBot-Result: golang...@luci-project-accounts.iam.gserviceaccount.com <golang...@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Junyang Shao <shaoj...@google.com>
Auto-Submit: Austin Clements <aus...@google.com>
Files:
- M src/simd/internal/spec/converts.go
- M src/simd/internal/spec/doc.go
Change size: S
Delta: 2 files changed, 11 insertions(+), 1 deletion(-)
Branch: refs/heads/master
Submit Requirements:
Code-Review: +2 by Junyang Shao
TryBots-Pass: LUCI-TryBot-Result+1 by golang...@luci-project-accounts.iam.gserviceaccount.com
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Reply all
Reply to author
Forward
0 new messages