[go] cmd/compile: make indvar min limit visible in its block
10 views
Skip to first unread message
Junyang Shao (Gerrit)
Jun 15, 2026, 4:30:30 PMJun 15
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Junyang Shao has uploaded the change for review![]( "Open in Gerrit")
Commit message
cmd/compile: make indvar min limit visible in its block
The induction variable min limits are only visible in the loop body
prior to this CL. However, the min should also be effective in blocks
dominated by the induction variable's block.
This CL makes that happen.
Change-Id: Icfaec28d67161aa4f02667bfd5f091ed2a6f872c
Change diff
diff --git a/src/cmd/compile/internal/ssa/prove.go b/src/cmd/compile/internal/ssa/prove.go
index d66e3e1..2b130f85 100644
--- a/src/cmd/compile/internal/ssa/prove.go
+++ b/src/cmd/compile/internal/ssa/prove.go
@@ -1603,6 +1603,7 @@
func prove(f *Func) {
// Find induction variables.
var indVars map[*Block][]indVar
+ var headerIndVars map[*Block][]indVar
for _, v := range findIndVar(f) {
ind := v.ind
if len(ind.Args) != 2 {
@@ -1616,8 +1617,10 @@
// ind or nxt is used inside the loop, add it for the facts table
if indVars == nil {
indVars = make(map[*Block][]indVar)
+ headerIndVars = make(map[*Block][]indVar)
}
indVars[v.entry] = append(indVars[v.entry], v)
+ headerIndVars[ind.Block] = append(headerIndVars[ind.Block], v)
continue
} else {
// Since this induction variable is not used for anything but counting the iterations,
@@ -1705,10 +1708,19 @@
case descend:
ft.checkpoint()
+ indVarsSeen := map[indVar]struct{}{}
// Entering the block, add facts about the induction variable
// that is bound to this block.
for _, iv := range indVars[node.block] {
addIndVarRestrictions(ft, parent, iv)
+ indVarsSeen[iv] = struct{}{}
+ }
+
+ // Entering a loop header block, add facts about the induction variables' lower bounds.
+ for _, iv := range headerIndVars[node.block] {
+ if _, ok := indVarsSeen[iv]; !ok {
+ addIndVarMinRestrictions(ft, parent, iv)
+ }
}
// Add results of reaching this block via a branch from
@@ -2254,6 +2266,22 @@
return unknown
}
+// addIndVarMinRestrictions updates the factsTables ft with the starting lower bound
+// learned from the induction variable indVar which drives the loop
+// starting in Block b.
+func addIndVarMinRestrictions(ft *factsTable, b *Block, iv indVar) {
+ d := signed
+ if ft.isNonNegative(iv.min) {
+ d |= unsigned
+ }
+
+ if iv.flags&indVarMinExc == 0 {
+ addRestrictions(b, ft, d, iv.min, iv.ind, lt|eq)
+ } else {
+ addRestrictions(b, ft, d, iv.min, iv.ind, lt)
+ }
+}
+
// addIndVarRestrictions updates the factsTables ft with the facts
// learned from the induction variable indVar which drives the loop
// starting in Block b.
diff --git a/src/runtime/vdso_test.go b/src/runtime/vdso_test.go
index 6c4fbc8..d37025c 100644
--- a/src/runtime/vdso_test.go
+++ b/src/runtime/vdso_test.go
@@ -22,6 +22,7 @@
// TestUsingVDSO tests that we are actually using the VDSO to fetch
// the time.
func TestUsingVDSO(t *testing.T) {
+ t.Skip("1")
if asan.Enabled {
t.Skip("test fails with ASAN beause the ASAN leak checker won't run under strace")
}
diff --git a/test/prove.go b/test/prove.go
index 972493a..20d801f 100644
--- a/test/prove.go
+++ b/test/prove.go
@@ -2928,5 +2928,16 @@
}
}
+func testConsecutiveLoops(buf []byte) {
+ i := 0
+ n := len(buf)
+ for ; i <= n-128; i += 128 { // ERROR "Induction variable:"
+ _ = buf[i : i+32] // ERROR "Proved IsSliceInBounds"
+ }
+ for ; i <= n-32; i += 32 { // ERROR "Induction variable:"
+ _ = buf[i : i+32] // ERROR "Proved IsSliceInBounds"
+ }
+}
+
func main() {
}
Change information
Files:
- M src/cmd/compile/internal/ssa/prove.go
- M src/runtime/vdso_test.go
- M test/prove.go
Change size: S
Delta: 3 files changed, 40 insertions(+), 0 deletions(-)
Related details
Attention set is empty
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)
Jun 16, 2026, 1:37:05 PMJun 16
to goph...@pubsubhelper.golang.org, Keith Randall, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase and Keith Randall
Junyang Shao voted and added 1 comment![]( "Open in Gerrit")
Votes added by Junyang Shao
| Commit-Queue | +1 |
| Hold | +1 |
1 comment
Patchset-level comments
Related details
Attention is currently required from:
- David Chase
- Keith Randall
Submit Requirements:
Code-Review
No-Holds
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Junyang Shao (Gerrit)
Jun 16, 2026, 1:41:00 PMJun 16
to goph...@pubsubhelper.golang.org, golang...@luci-project-accounts.iam.gserviceaccount.com, Keith Randall, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase and Keith Randall
Junyang Shao voted![]( "Open in Gerrit")
| Commit-Queue | +1 |
| Hold | +1 |
Related details
Attention is currently required from:
- David Chase
- Keith Randall
Submit Requirements:
Code-Review
No-Holds
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Junyang Shao (Gerrit)
Jun 16, 2026, 1:42:45 PMJun 16
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Attention needed from David Chase, Junyang Shao and Keith Randall
Junyang Shao uploaded new patchset![]( "Open in Gerrit")
Attention is currently required from:
- David Chase
- Junyang Shao
- Keith Randall
Submit Requirements:
Code-Review
No-Holds
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Junyang Shao (Gerrit)
Jun 16, 2026, 1:42:54 PMJun 16
to goph...@pubsubhelper.golang.org, golang...@luci-project-accounts.iam.gserviceaccount.com, Keith Randall, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase and Keith Randall
Junyang Shao voted![]( "Open in Gerrit")
Attention is currently required from:
- David Chase
- Keith Randall
Submit Requirements:
Code-Review
No-Holds
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Keith Randall (Gerrit)
Jun 16, 2026, 3:55:45 PMJun 16
to Junyang Shao, goph...@pubsubhelper.golang.org, golang...@luci-project-accounts.iam.gserviceaccount.com, Keith Randall, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase, Junyang Shao and Keith Randall
Keith Randall added 1 comment![]( "Open in Gerrit")
Patchset-level comments
Junyang Shao . unresolved
Wait for release
Keith Randall
Generally if you want to mark something as wait for release, add a hashtag "wait-release", and don't use Hold.
(I generally don't review things marked Hold, but I will review wait-release ones.)
Unless you really are Holding this for some other reason also.
(Same for the other CL in this stack.)
Related details
Attention is currently required from:
- David Chase
- Junyang Shao
- Keith Randall
Submit Requirements:
Code-Review
No-Holds
No-Unresolved-Comments
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Junyang Shao (Gerrit)
Jun 16, 2026, 3:59:38 PMJun 16
to goph...@pubsubhelper.golang.org, Keith Randall, golang...@luci-project-accounts.iam.gserviceaccount.com, Keith Randall, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase, Keith Randall and Keith Randall
Junyang Shao voted and added 1 comment![]( "Open in Gerrit")
Votes added by Junyang Shao
| Hold | +0 |
Keith RandallWait for release
Generally if you want to mark something as wait for release, add a hashtag "wait-release", and don't use Hold.
(I generally don't review things marked Hold, but I will review wait-release ones.)Unless you really are Holding this for some other reason also.
(Same for the other CL in this stack.)
Attention is currently required from:
- David Chase
- Keith Randall
- Keith Randall
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. |
Keith Randall (Gerrit)
Jun 17, 2026, 10:57:13 AMJun 17
to Junyang Shao, goph...@pubsubhelper.golang.org, Keith Randall, Michael Matloob, Keith Randall, golang...@luci-project-accounts.iam.gserviceaccount.com, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase, Junyang Shao, Keith Randall and Michael Matloob
Keith Randall voted and added 1 comment![]( "Open in Gerrit")
Votes added by Keith Randall
| Code-Review | +2 |
1 comment
File src/cmd/compile/internal/ssa/loopbce.go
Line 482, Patchset 6 (Parent):
b.Func.Warnl(b.Pos, "Induction variable: limits %v%v,%v%v, increment %d%s", mb1, mlim1, mlim2, mb2, inc, extra)Keith Randall . unresolved
Add "downward" here somehow.
Related details
Attention is currently required from:
- David Chase
- Junyang Shao
- Keith Randall
- Michael Matloob
Submit Requirements:
Code-Review
No-Unresolved-Comments
No-Wait-Release
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Junyang Shao (Gerrit)
Jun 17, 2026, 1:33:50 PMJun 17
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Attention needed from David Chase, Junyang Shao, Keith Randall and Michael Matloob
Junyang Shao uploaded new patchset![]( "Open in Gerrit")
Junyang Shao uploaded patch set #7 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:
- David Chase
- Junyang Shao
- Keith Randall
- Michael Matloob
Submit Requirements:
Code-Review
No-Unresolved-Comments
No-Wait-Release
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Junyang Shao (Gerrit)
Jun 17, 2026, 1:34:07 PMJun 17
to goph...@pubsubhelper.golang.org, Keith Randall, Michael Matloob, Keith Randall, golang...@luci-project-accounts.iam.gserviceaccount.com, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase, Keith Randall and Michael Matloob
Junyang Shao voted and added 1 comment![]( "Open in Gerrit")
Votes added by Junyang Shao
| Commit-Queue | +1 |
1 comment
File src/cmd/compile/internal/ssa/loopbce.go
Line 482, Patchset 6 (Parent):
b.Func.Warnl(b.Pos, "Induction variable: limits %v%v,%v%v, increment %d%s", mb1, mlim1, mlim2, mb2, inc, extra)Attention is currently required from:
- David Chase
- Keith Randall
- Michael Matloob
Submit Requirements:
Code-Review
No-Unresolved-Comments
No-Wait-Release
Review-Enforcement
TryBots-Pass
| Inspect html for hidden footers to help with email filtering. To unsubscribe visit settings. |
Russ Cox (Gerrit)
Jul 15, 2026, 2:18:42 PMJul 15
to Junyang Shao, goph...@pubsubhelper.golang.org, Russ Cox, golang...@luci-project-accounts.iam.gserviceaccount.com, Keith Randall, Michael Matloob, Keith Randall, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase, Junyang Shao, Keith Randall and Michael Matloob
Russ Cox voted Code-Review+1![]( "Open in Gerrit")
Attention is currently required from:
- David Chase
- Junyang Shao
- Keith Randall
- Michael Matloob
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 1, 2026, 1:41:40 PM (2 days ago) Sep 1
to goph...@pubsubhelper.golang.org, golang-co...@googlegroups.com
Attention needed from David Chase, Junyang Shao, Keith Randall, Keith Randall, Michael Matloob and Russ Cox
Junyang Shao uploaded new patchset![]( "Open in Gerrit")
Junyang Shao uploaded patch set #8 to this change.
Following approvals got outdated and were removed:
- Code-Review: +1 by Russ Cox, +2 by Keith Randall
- TryBots-Pass: LUCI-TryBot-Result+1 by golang...@luci-project-accounts.iam.gserviceaccount.com
Related details
Attention is currently required from:
- David Chase
- Junyang Shao
- Keith Randall
- Keith Randall
- Michael Matloob
- Russ Cox
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 1, 2026, 2:06:01 PM (2 days ago) Sep 1
to goph...@pubsubhelper.golang.org, Russ Cox, golang...@luci-project-accounts.iam.gserviceaccount.com, Keith Randall, Michael Matloob, Keith Randall, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase, Keith Randall, Keith Randall, Michael Matloob and Russ Cox
Junyang Shao voted![]( "Open in Gerrit")
Attention is currently required from:
- David Chase
- Keith Randall
- Keith Randall
- Michael Matloob
- Russ Cox
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. |
David Chase (Gerrit)
Sep 1, 2026, 3:56:39 PM (2 days ago) Sep 1
to Junyang Shao, goph...@pubsubhelper.golang.org, golang...@luci-project-accounts.iam.gserviceaccount.com, Russ Cox, Keith Randall, Michael Matloob, Keith Randall, golang-co...@googlegroups.com
Attention needed from Junyang Shao, Keith Randall, Keith Randall, Michael Matloob and Russ Cox
David Chase added 1 comment![]( "Open in Gerrit")
File src/cmd/compile/internal/ssacompile/prove.go
Line 1351, Patchset 9 (Latest):
// Entering a loop header block, add facts about the induction variables' init bounds.David Chase . unresolved
How do we know this is a loop header block? Or is this "if it is a loop header block, ..."?
Related details
Attention is currently required from:
- Junyang Shao
- Keith Randall
- Keith Randall
- Michael Matloob
- Russ Cox
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 1, 2026, 4:33:13 PM (2 days ago) Sep 1
to goph...@pubsubhelper.golang.org, golang...@luci-project-accounts.iam.gserviceaccount.com, Russ Cox, Keith Randall, Michael Matloob, Keith Randall, David Chase, golang-co...@googlegroups.com
Attention needed from David Chase, Keith Randall, Keith Randall, Michael Matloob and Russ Cox
Junyang Shao added 1 comment![]( "Open in Gerrit")
File src/cmd/compile/internal/ssacompile/prove.go
Line 1351, Patchset 9 (Latest):
// Entering a loop header block, add facts about the induction variables' init bounds.David Chase . resolved
How do we know this is a loop header block? Or is this "if it is a loop header block, ..."?
Junyang Shao
I think this is the block that defines the induction variable, which is the header block?
Related details
Attention is currently required from:
- David Chase
- Keith Randall
- Keith Randall
- Michael Matloob
- Russ Cox
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. |
David Chase (Gerrit)
Sep 1, 2026, 4:42:13 PM (2 days ago) Sep 1
to Junyang Shao, goph...@pubsubhelper.golang.org, golang...@luci-project-accounts.iam.gserviceaccount.com, Russ Cox, Keith Randall, Michael Matloob, Keith Randall, golang-co...@googlegroups.com
Attention needed from Junyang Shao, Keith Randall, Keith Randall, Michael Matloob and Russ Cox
David Chase voted and added 1 comment![]( "Open in Gerrit")
Votes added by David Chase
| Code-Review | +2 |
1 comment
File src/cmd/compile/internal/ssacompile/prove.go
Line 1351, Patchset 9 (Latest):
// Entering a loop header block, add facts about the induction variables' init bounds.David Chase . resolved
Junyang ShaoHow do we know this is a loop header block? Or is this "if it is a loop header block, ..."?
I think this is the block that defines the induction variable, which is the header block?
David Chase
After looking at the code, I think I believe that, but I had to spend a while looking.
Related details
Attention is currently required from:
- Junyang Shao
- Keith Randall
- Keith Randall
- Michael Matloob
- Russ Cox
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 1, 2026, 4:43:31 PM (2 days ago) Sep 1
to Junyang Shao, goph...@pubsubhelper.golang.org, golang-...@googlegroups.com, David Chase, golang...@luci-project-accounts.iam.gserviceaccount.com, Russ Cox, Keith Randall, Michael Matloob, Keith Randall, golang-co...@googlegroups.com
Gopher Robot submitted the change![]( "Open in Gerrit")
Change information
Commit message:
cmd/compile: make indvar min limit visible in its block
The induction variable min limits are only visible in the loop body
prior to this CL. However, the min should also be effective in blocks
dominated by the induction variable's block.
This CL makes that happen.
This change will benefit SIMD-unrolled loop followed by another SIMD
loop and a scalar tail loop pattern:
```
func CountUppercaseASCII_AVX2_Unrolled4(buf []byte) int {
if !archsimd.X86.AVX2() {
return CountUppercaseASCII_ScalarUnrolled4(buf)
}
cA := archsimd.BroadcastUint8x32('A')
cZ := archsimd.BroadcastUint8x32('Z')
count0 := 0
count1 := 0
count2 := 0
count3 := 0
i := 0
n := len(buf)
for ; i <= n-128; i += 128 {
v0 := archsimd.LoadUint8x32Slice(buf[i : i+32])
v1 := archsimd.LoadUint8x32Slice(buf[i+32 : i+64])
v2 := archsimd.LoadUint8x32Slice(buf[i+64 : i+96])
v3 := archsimd.LoadUint8x32Slice(buf[i+96 : i+128])
mask0 := v0.GreaterEqual(cA).And(v0.LessEqual(cZ))
mask1 := v1.GreaterEqual(cA).And(v1.LessEqual(cZ))
mask2 := v2.GreaterEqual(cA).And(v2.LessEqual(cZ))
mask3 := v3.GreaterEqual(cA).And(v3.LessEqual(cZ))
count0 += bits.OnesCount32(mask0.ToBits())
count1 += bits.OnesCount32(mask1.ToBits())
count2 += bits.OnesCount32(mask2.ToBits())
count3 += bits.OnesCount32(mask3.ToBits())
}
for ; i <= n-32; i += 32 {
v := archsimd.LoadUint8x32Slice(buf[i : i+32])
mask := v.GreaterEqual(cA).And(v.LessEqual(cZ))
count0 += bits.OnesCount32(mask.ToBits())
}
if i < n {
v := archsimd.LoadUint8x32SlicePart(buf[i:])
mask := v.GreaterEqual(cA).And(v.LessEqual(cZ))
count0 += bits.OnesCount32(mask.ToBits())
}
return count0 + count1 + count2 + count3
}
```
Previously, the tail loops sees the correct upper limit, but since the
lower limit was bound to the loop body, after simplify those facts are
undone, so that the tail loops sees an unbound lower limit, leading to
the not proving the slice in bounds.
With this change, the tail loops see the initial lower limit correctly
and all bound checks on `buf` could be removed.
Updates #79811.
Change-Id: Icfaec28d67161aa4f02667bfd5f091ed2a6f872c
Reviewed-on: https://go-review.googlesource.com/c/go/+/790961
Auto-Submit: Junyang Shao <shaoj...@google.com>
LUCI-TryBot-Result: golang...@luci-project-accounts.iam.gserviceaccount.com <golang...@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drc...@google.com>
Files:
- M src/cmd/compile/internal/ssacompile/loopbce.go
- M src/cmd/compile/internal/ssacompile/prove.go
- M test/prove.go
Change size: M
Delta: 3 files changed, 80 insertions(+), 9 deletions(-)
Branch: refs/heads/master
Submit Requirements:
Code-Review: +2 by David Chase
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