[RISC-V] Improve clamped subtract & increment by tomeksowi · Pull Request #118530 · dotnet/runtime

tomeksowi · 2025-08-08T12:57:39Z

Improve codegens with hardcoded subtract clamped to 0 (in localloc) and increment clamped to maximum (in inc_saturate).

Part of #84834, cc @dotnet/samsung

dotnet-policy-service · 2025-08-08T12:58:30Z

Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch
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tomeksowi · 2025-08-08T13:05:26Z

For future PRs: these constructs are a good candidate to augment the if-conversion pass (#116581)

tomeksowi · 2025-08-08T13:21:55Z

Diffs are based on 172,775 contexts (51,182 MinOpts, 121,593 FullOpts).

Overall (-256 bytes)

Collection	Base size (bytes)	Diff size (bytes)	PerfScore in Diffs
linux.riscv64.Checked.2.mch	163,287,100	-256	-0.01%

MinOpts (-8 bytes)

Collection	Base size (bytes)	Diff size (bytes)	PerfScore in Diffs
linux.riscv64.Checked.2.mch	90,082,492	-8	-0.00%

FullOpts (-248 bytes)

Collection	Base size (bytes)	Diff size (bytes)	PerfScore in Diffs
linux.riscv64.Checked.2.mch	73,204,608	-248	-0.01%

Example diffs

linux.riscv64.Checked.2.mch

-12 (-5.36%) : 38740.dasm - StackallocTests:Test20000_SkipLocalsInit(byref):System.Guid (FullOpts)

@@ -41,17 +41,14 @@ G_M62621_IG02:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0200 {s1}, byre
             jalr           a0		// <unknown method>
             lui            a0, 0xD1FFAB1E
             addiw          a0, a0, 0xD1FFAB1E
-            sltu           a1, sp, a0
-            sub            a0, sp, a0
-            beqz           a1, pc+8 (2 instructions)
-            mv             a0, zero
+            maxu           a1, sp, a0
+            sub            a0, a1, a0
             lui            a2, 0xD1FFAB1E
             mv             a1, sp
             lw             zero, 0xD1FFAB1E(a1)
             sub            a1, a1, a2
             bgeu           a1, a0, pc-8 (-2 instructions)
             mv             sp, a0
-            mv             a0, sp
             lui            t6, 0xD1FFAB1E
             addiw          t6, t6, 0xD1FFAB1E
             slli           t6, t6, 16
@@ -70,7 +67,7 @@ G_M62621_IG02:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0200 {s1}, byre
             auipc          ra, 0xD1FFAB1E
             jalr           ra		// CORINFO_HELP_FAIL_FAST
             ; byrRegs -[s1]
-						;; size=140 bbWeight=1 PerfScore 62.50
+						;; size=128 bbWeight=1 PerfScore 58.00
 G_M62621_IG03:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0000 {}, byref, epilog, nogc
             addi           sp, fp, -24
             ld             s1, 40(sp)
@@ -81,7 +78,7 @@ G_M62621_IG03:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0000 {}, byref,
 RWD00  	dq	9ABCDEF012345678h
 
 
-; Total bytes of code 224, prolog size 56, PerfScore 98.00, instruction count 42, allocated bytes for code 224 (MethodHash=43680b62) for method StackallocTests:Test20000_SkipLocalsInit(byref):System.Guid (FullOpts)
+; Total bytes of code 212, prolog size 56, PerfScore 93.50, instruction count 39, allocated bytes for code 212 (MethodHash=43680b62) for method StackallocTests:Test20000_SkipLocalsInit(byref):System.Guid (FullOpts)
 ; ============================================================
 
 Unwind Info:
@@ -92,7 +89,7 @@ Unwind Info:
   E bit             : 0
   X bit             : 0
   Vers              : 0
-  Function Length   : 56 (0x00038) Actual length = 224 (0x0000e0)
+  Function Length   : 53 (0x00035) Actual length = 212 (0x0000d4)
   ---- Epilog scopes ----
   ---- Scope 0
   Epilog Start Offset        : 3523193630 (0xd1ffab1e) Actual offset = 3523193630 (0xd1ffab1e) Offset from main function begin = 3523193630 (0xd1ffab1e)

-8 (-2.35%) : 124769.dasm - T:dirtyStack() (MinOpts)

@@ -61,18 +61,16 @@ G_M4777_IG04:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0000 {}, byref
             mv             a1, a0
             addi           a1, a1, 0xD1FFAB1E
             andi           a1, a1, -16
-            sltu           a2, sp, a1
-            sub            a1, sp, a1
-            beqz           a2, pc+8 (2 instructions)
-            mv             a1, zero
+            maxu           a2, sp, a1
+            sub            a1, a2, a1
             lui            a3, 0xD1FFAB1E
             mv             a2, sp
             lw             zero, 0xD1FFAB1E(a2)
             sub            a2, a2, a3
             bgeu           a2, a1, pc-8 (-2 instructions)
             mv             sp, a1
-            mv             a0, sp
-						;; size=88 bbWeight=1 PerfScore 25.50
+            mv             a0, a1
+						;; size=80 bbWeight=1 PerfScore 21.50
 G_M4777_IG05:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0000 {}, byref
             sd             a0, -8(fp)
             sw             zero, -12(fp)
@@ -119,7 +117,7 @@ G_M4777_IG08:        ; bbWeight=1, gcrefRegs=0000 {}, byrefRegs=0000 {}, byref,
 RWD00  	dq	9ABCDEF012345678h
 
 
-; Total bytes of code 340, prolog size 52, PerfScore 123.00, instruction count 60, allocated bytes for code 340 (MethodHash=759ced56) for method T:dirtyStack() (MinOpts)
+; Total bytes of code 332, prolog size 52, PerfScore 119.00, instruction count 58, allocated bytes for code 332 (MethodHash=759ced56) for method T:dirtyStack() (MinOpts)
 ; ============================================================
 
 Unwind Info:
@@ -130,7 +128,7 @@ Unwind Info:
   E bit             : 0
   X bit             : 0
   Vers              : 0
-  Function Length   : 85 (0x00055) Actual length = 340 (0x000154)
+  Function Length   : 83 (0x00053) Actual length = 332 (0x00014c)
   ---- Epilog scopes ----
   ---- Scope 0
   Epilog Start Offset        : 3523193630 (0xd1ffab1e) Actual offset = 3523193630 (0xd1ffab1e) Offset from main function begin = 3523193630 (0xd1ffab1e)

-24 (-1.46%) : 599.dasm - (dynamicClass):IL_STUB_PInvoke(int,System.String,System.String,System.String):int (FullOpts)

@@ -139,18 +139,16 @@ G_M26182_IG05:        ; bbWeight=0.50, gcrefRegs=C0200 {s1 s2 s3}, byrefRegs=000
             mv             a0, a2
             addi           a0, a0, 0xD1FFAB1E
             andi           a0, a0, -16
-            sltu           a1, sp, a0
-            sub            a0, sp, a0
-            beqz           a1, pc+8 (2 instructions)
-            mv             a0, zero
+            maxu           a1, sp, a0
+            sub            a0, a1, a0
             lui            a3, 0xD1FFAB1E
             mv             a1, sp
             lw             zero, 0xD1FFAB1E(a1)
             sub            a1, a1, a3
             bgeu           a1, a0, pc-8 (-2 instructions)
             mv             sp, a0
-            mv             a2, sp
-						;; size=116 bbWeight=0.50 PerfScore 19.00
+            mv             a2, a0
+						;; size=108 bbWeight=0.50 PerfScore 17.00
 G_M26182_IG06:        ; bbWeight=0.50, gcrefRegs=C0200 {s1 s2 s3}, byrefRegs=0000 {}, byref
             sd             a2, -24(fp)
 						;; size=4 bbWeight=0.50 PerfScore 2.00
@@ -208,18 +206,16 @@ G_M26182_IG09:        ; bbWeight=0.50, gcrefRegs=C0000 {s2 s3}, byrefRegs=0000 {
             mv             a0, a2
             addi           a0, a0, 0xD1FFAB1E
             andi           a0, a0, -16
-            sltu           a1, sp, a0
-            sub            a0, sp, a0
-            beqz           a1, pc+8 (2 instructions)
-            mv             a0, zero
+            maxu           a1, sp, a0
+            sub            a0, a1, a0
             lui            a3, 0xD1FFAB1E
             mv             a1, sp
             lw             zero, 0xD1FFAB1E(a1)
             sub            a1, a1, a3
             bgeu           a1, a0, pc-8 (-2 instructions)
             mv             sp, a0
-            mv             a2, sp
-						;; size=116 bbWeight=0.50 PerfScore 19.00
+            mv             a2, a0
+						;; size=108 bbWeight=0.50 PerfScore 17.00
 G_M26182_IG10:        ; bbWeight=0.50, gcrefRegs=C0000 {s2 s3}, byrefRegs=0000 {}, byref
             sd             a2, -40(fp)
 						;; size=4 bbWeight=0.50 PerfScore 2.00
@@ -277,18 +273,16 @@ G_M26182_IG13:        ; bbWeight=0.50, gcrefRegs=80000 {s3}, byrefRegs=0000 {},
             mv             a0, a2
             addi           a0, a0, 0xD1FFAB1E
             andi           a0, a0, -16
-            sltu           a1, sp, a0
-            sub            a0, sp, a0
-            beqz           a1, pc+8 (2 instructions)
-            mv             a0, zero
+            maxu           a1, sp, a0
+            sub            a0, a1, a0
             lui            a3, 0xD1FFAB1E
             mv             a1, sp
             lw             zero, 0xD1FFAB1E(a1)
             sub            a1, a1, a3
             bgeu           a1, a0, pc-8 (-2 instructions)
             mv             sp, a0
-            mv             a2, sp
-						;; size=116 bbWeight=0.50 PerfScore 19.00
+            mv             a2, a0
+						;; size=108 bbWeight=0.50 PerfScore 17.00
 G_M26182_IG14:        ; bbWeight=0.50, gcrefRegs=80000 {s3}, byrefRegs=0000 {}, byref
             sd             a2, -56(fp)
 						;; size=4 bbWeight=0.50 PerfScore 2.00
@@ -556,7 +550,7 @@ G_M26182_IG34:        ; bbWeight=0, gcrefRegs=0000 {}, byrefRegs=0000 {}, byref,
 RWD00  	dq	9ABCDEF012345678h
 
 
-; Total bytes of code 1640, prolog size 116, PerfScore 396.75, instruction count 311, allocated bytes for code 1640 (MethodHash=57cb99b9) for method (dynamicClass):IL_STUB_PInvoke(int,System.String,System.String,System.String):int (FullOpts)
+; Total bytes of code 1616, prolog size 116, PerfScore 390.75, instruction count 305, allocated bytes for code 1616 (MethodHash=57cb99b9) for method (dynamicClass):IL_STUB_PInvoke(int,System.String,System.String,System.String):int (FullOpts)
 ; ============================================================
 
 Unwind Info:
@@ -567,7 +561,7 @@ Unwind Info:
   E bit             : 0
   X bit             : 0
   Vers              : 0
-  Function Length   : 336 (0x00150) Actual length = 1344 (0x000540)
+  Function Length   : 330 (0x0014a) Actual length = 1320 (0x000528)
   ---- Epilog scopes ----
   ---- Scope 0
   Epilog Start Offset        : 3523193630 (0xd1ffab1e) Actual offset = 3523193630 (0xd1ffab1e) Offset from main function begin = 3523193630 (0xd1ffab1e)

+0 (0.00%) : 172672.dasm - Microsoft.Diagnostics.Tracing.ZippedETLWriter:GetNGenPdbs(System.String,Microsoft.Diagnostics.Symbols.SymbolReader,System.IO.TextWriter):System.Collections.Generic.List`1[System.String] (FullOpts)

No diffs found?

+0 (0.00%) : 171872.dasm - Microsoft.Diagnostics.Symbols.SymbolReader:BypassSystem32FileRedirection(System.String):System.String (FullOpts)

No diffs found?

+0 (0.00%) : 171504.dasm - JIT.HardwareIntrinsics.X86._Avx512DQ.UnaryOpTest__ConvertToVector512Int64DoubletoInt64ToPositiveInfinity+TestStruct:Create():JIT.HardwareIntrinsics.X86._Avx512DQ.UnaryOpTest__ConvertToVector512Int64DoubletoInt64ToPositiveInfinity+TestStruct (MinOpts)

No diffs found?

Details

Size improvements/regressions per collection

Collection	Contexts with diffs	Improvements	Regressions	Same size	Improvements (bytes)	Regressions (bytes)
linux.riscv64.Checked.2.mch	3,875	21	0	3,854	-256	+0

PerfScore improvements/regressions per collection

Collection	Contexts with diffs	Improvements	Regressions	Same PerfScore	Improvements (PerfScore)	Regressions (PerfScore)	PerfScore Overall in FullOpts
linux.riscv64.Checked.2.mch	3,875	18	0	3,857	-1.30%	0.00%	-0.0002%

Context information

Collection	Diffed contexts	MinOpts	FullOpts	Missed, base	Missed, diff
linux.riscv64.Checked.2.mch	172,775	51,182	121,593	0 (0.00%)	0 (0.00%)

jit-analyze output

tomeksowi · 2025-08-08T13:24:35Z

@risc-vv /run

risc-vv · 2025-08-08T13:26:22Z

RISC-V pull_request-CLR-QEMU: 9092 / 9131 (99.57%)

=======================
      passed: 9092
      failed: 11
     skipped: 591
      killed: 28
------------------------
 TOTAL tests: 9722
VIRTUAL time: 80h 45min 8s 50ms
   REAL time: 1h 19min 11s 659ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V pull_request-CLR-VF2: 9091 / 9130 (99.57%)

=======================
      passed: 9091
      failed: 11
     skipped: 591
      killed: 28
------------------------
 TOTAL tests: 9721
VIRTUAL time: 32h 11min 28s 894ms
   REAL time: 2h 7min 52s 50ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V pull_request-FX-QEMU: 0 / 1 (0.00%)

=======================
      passed: 0
      failed: 0
     skipped: 14
      killed: 1
------------------------
 TOTAL tests: 15
VIRTUAL time: 15s 614ms
   REAL time: 4h 30min 0s 481ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V pull_request-FX-VF2: 0 / 62 (0.00%)

=======================
      passed: 0
      failed: 0
     skipped: 14
      killed: 62
------------------------
 TOTAL tests: 76
VIRTUAL time: 1min 13s 210ms
   REAL time: 12h 30min 11s 419ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

Build information and commands

GIT: 18409167809f6f9ad15fcedba0c759fd9af1c045
CI: d023c7d591ab286aa343d644f00b5daa59d8d6b0
REPO: dotnet/runtime
BRANCH: main
CONFIG: Checked
LIB_CONFIG: Release

tomeksowi · 2025-08-11T10:00:17Z

@risc-vv /run

risc-vv · 2025-08-11T10:01:41Z

RISC-V pull_request-CLR-QEMU: 9101 / 9131 (99.67%)

=======================
      passed: 9101
      failed: 2
     skipped: 591
      killed: 28
------------------------
 TOTAL tests: 9722
VIRTUAL time: 80h 40min 33s 749ms
   REAL time: 1h 19min 1s 939ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V pull_request-CLR-VF2: 9101 / 9131 (99.67%)

=======================
      passed: 9101
      failed: 2
     skipped: 591
      killed: 28
------------------------
 TOTAL tests: 9722
VIRTUAL time: 32h 8min 38s 482ms
   REAL time: 2h 7min 39s 653ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V pull_request-FX-QEMU: 0 / 0 (100.00%)

=======================
      passed: 0
      failed: 0
     skipped: 14
      killed: 0
------------------------
 TOTAL tests: 14
VIRTUAL time: 0ms
   REAL time: 4h 30min 0s 520ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

RISC-V pull_request-FX-VF2: 0 / 58 (0.00%)

=======================
      passed: 0
      failed: 0
     skipped: 14
      killed: 58
------------------------
 TOTAL tests: 72
VIRTUAL time: 1min 8s 984ms
   REAL time: 13h 0min 6s 814ms
=======================

report.xml, report.md, failures.xml, testclr_details.tar.zst

Build information and commands

GIT: b1572f8f2118702ca0bad2fa95d58beb6bd5f748
CI: d023c7d591ab286aa343d644f00b5daa59d8d6b0
REPO: dotnet/runtime
BRANCH: main
CONFIG: Checked
LIB_CONFIG: Release

JulieLeeMSFT · 2025-10-06T19:54:57Z

We will review .NET 11 PRs when we are done with .NET 10 last minute works and less busy. Please give us a few more weeks.
CC @jakobbotsch.

github-actions bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Aug 8, 2025

dotnet-policy-service bot added the community-contribution Indicates that the PR has been added by a community member label Aug 8, 2025

tomeksowi marked this pull request as draft August 8, 2025 13:24

build-analysis bot mentioned this pull request Aug 8, 2025

BinderTracingTest.ResolutionFlow times out #104670

Open

am11 added the arch-riscv Related to the RISC-V architecture label Aug 9, 2025

tomeksowi added 6 commits August 11, 2025 11:41

Improve clamped subtract for localloc

bdee11d

Clamped increment for IncSaturate

eb7d246

Use target reg as temp for comparison result

0d12210

Fix returning stackalloc'ed address

836734d

Fix instruction order, remove pointless diffs

d7adaf8

Revert adding to sp in stackAdjustment case

b1572f8

tomeksowi force-pushed the clamped-sub-inc branch from 1840916 to b1572f8 Compare August 11, 2025 09:52

tomeksowi marked this pull request as ready for review August 11, 2025 13:35

clamp03 assigned tomeksowi Aug 12, 2025

Merge branch 'main' into clamped-sub-inc (resolve conflicts)

3e56346

steveisok added this to the 11.0.0 milestone Oct 6, 2025

jakobbotsch approved these changes Oct 21, 2025

View reviewed changes

jakobbotsch merged commit 25e088f into dotnet:main Oct 21, 2025
117 checks passed

dotnet-maestro bot mentioned this pull request Oct 21, 2025

[main] Source code updates from dotnet/runtime dotnet/dotnet#3024

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[RISC-V] Improve clamped subtract & increment#118530

[RISC-V] Improve clamped subtract & increment#118530
jakobbotsch merged 7 commits intodotnet:mainfrom
tomeksowi:clamped-sub-inc

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Size improvements/regressions per collection

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