[llvm-branch-commits] [llvm] 4250a0f - [RISCV] Fix stackmap shadow trimming NOP size for compressed targets (#189774)

[Cullen Rhodes via llvm-branch-commits]

Author: Jim Lin
Date: 2026-04-02T07:02:15Z
New Revision: 4250a0fc5de96604d76a86158b41a5e988c4979a

URL: https://github.com/llvm/llvm-project/commit/4250a0fc5de96604d76a86158b41a5e988c4979a
DIFF: https://github.com/llvm/llvm-project/commit/4250a0fc5de96604d76a86158b41a5e988c4979a.diff

LOG: [RISCV] Fix stackmap shadow trimming NOP size for compressed targets (#189774)

The shadow trimming loop in LowerSTACKMAP hardcoded a 4-byte decrement
per instruction, but when Zca is enabled NOPs are 2 bytes. Use NOPBytes
instead of the hardcoded 4 so the shadow is correctly trimmed on
compressed targets.

Co-authored-by: Claude Opus 4.6 <noreply at anthropic.com>
(cherry picked from commit 3d7eedce5658c41a1b22775938359bfafac47fc9)

Added: 
    

Modified: 
    llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
    llvm/test/CodeGen/RISCV/rv64-stackmap-nops.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp b/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
index 3baa5d06b0bf1..bb5c3338497c6 100644
--- a/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
+++ b/llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
@@ -155,7 +155,7 @@ void RISCVAsmPrinter::LowerSTACKMAP(MCStreamer &OutStreamer, StackMaps &SM,
         MII->getOpcode() == TargetOpcode::STACKMAP)
       break;
     ++MII;
-    NumNOPBytes -= 4;
+    NumNOPBytes -= NOPBytes;
   }
 
   // Emit nops.

diff  --git a/llvm/test/CodeGen/RISCV/rv64-stackmap-nops.ll b/llvm/test/CodeGen/RISCV/rv64-stackmap-nops.ll
index 68a7702a3df68..96d7f3349695d 100644
--- a/llvm/test/CodeGen/RISCV/rv64-stackmap-nops.ll
+++ b/llvm/test/CodeGen/RISCV/rv64-stackmap-nops.ll
@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
-; RUN: llc < %s -mtriple=riscv64 | FileCheck %s
+; RUN: llc < %s -mtriple=riscv64 | FileCheck %s --check-prefix=CHECK
+; RUN: llc < %s -mtriple=riscv64 -mattr=+c | FileCheck %s --check-prefix=RVC
 
 define void @test_shadow_optimization() {
 ; CHECK-LABEL: test_shadow_optimization:
@@ -9,8 +10,19 @@ define void @test_shadow_optimization() {
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    nop
 ; CHECK-NEXT:    ret
+;
+; RVC-LABEL: test_shadow_optimization:
+; RVC:       # %bb.0: # %entry
+; RVC-NEXT:  .Ltmp0:
+; RVC-NEXT:    nop
+; RVC-NEXT:    nop
+; RVC-NEXT:    nop
+; RVC-NEXT:    nop
+; RVC-NEXT:    nop
+; RVC-NEXT:    nop
+; RVC-NEXT:    nop
+; RVC-NEXT:    ret
 entry:
   tail call void (i64, i32, ...) @llvm.experimental.stackmap(i64  0, i32  16)
   ret void
 }
-