[llvm-branch-commits] [llvm] release/21.x: [RISCV] Correct the CFA offsets for stack probing. (#166616) (PR #166783)

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https://github.com/dyung updated https://github.com/llvm/llvm-project/pull/166783

>From 14387e80e18871671bc7dd761822f2853d9476a5 Mon Sep 17 00:00:00 2001
From: Craig Topper <craig.topper at sifive.com>
Date: Thu, 6 Nov 2025 07:09:52 -0800
Subject: [PATCH] [RISCV] Correct the CFA offsets for stack probing. (#166616)

We need to take into account that we may have already done a FirstSPAdjust.

Fixes #164805.

(cherry picked from commit ff11b93bb8f5578c9eb7296160570ea001a1155f)
---
 llvm/lib/Target/RISCV/RISCVFrameLowering.cpp         | 6 ++++--
 llvm/test/CodeGen/RISCV/rvv/stack-probing-dynamic.ll | 8 ++++----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
index 6c8e3da80b932..c4f41b8d8e4d9 100644
--- a/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ b/llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -768,6 +768,8 @@ void RISCVFrameLowering::allocateStack(MachineBasicBlock &MBB,
 
   // Unroll the probe loop depending on the number of iterations.
   if (Offset < ProbeSize * 5) {
+    uint64_t CFAAdjust = RealStackSize - Offset;
+
     uint64_t CurrentOffset = 0;
     while (CurrentOffset + ProbeSize <= Offset) {
       RI->adjustReg(MBB, MBBI, DL, SPReg, SPReg,
@@ -781,7 +783,7 @@ void RISCVFrameLowering::allocateStack(MachineBasicBlock &MBB,
 
       CurrentOffset += ProbeSize;
       if (EmitCFI)
-        CFIBuilder.buildDefCFAOffset(CurrentOffset);
+        CFIBuilder.buildDefCFAOffset(CurrentOffset + CFAAdjust);
     }
 
     uint64_t Residual = Offset - CurrentOffset;
@@ -789,7 +791,7 @@ void RISCVFrameLowering::allocateStack(MachineBasicBlock &MBB,
       RI->adjustReg(MBB, MBBI, DL, SPReg, SPReg,
                     StackOffset::getFixed(-Residual), Flag, getStackAlign());
       if (EmitCFI)
-        CFIBuilder.buildDefCFAOffset(Offset);
+        CFIBuilder.buildDefCFAOffset(RealStackSize);
 
       if (DynAllocation) {
         // s[d|w] zero, 0(sp)
diff --git a/llvm/test/CodeGen/RISCV/rvv/stack-probing-dynamic.ll b/llvm/test/CodeGen/RISCV/rvv/stack-probing-dynamic.ll
index d666832cf6e0b..c79fb0f91b21f 100644
--- a/llvm/test/CodeGen/RISCV/rvv/stack-probing-dynamic.ll
+++ b/llvm/test/CodeGen/RISCV/rvv/stack-probing-dynamic.ll
@@ -460,9 +460,9 @@ define void @reserved_call_frame(i64 %n) #0 {
 ; RV64I-NEXT:    lui a0, 1
 ; RV64I-NEXT:    sub sp, sp, a0
 ; RV64I-NEXT:    sd zero, 0(sp)
-; RV64I-NEXT:    .cfi_def_cfa_offset 4096
+; RV64I-NEXT:    .cfi_def_cfa_offset 6128
 ; RV64I-NEXT:    addi sp, sp, -48
-; RV64I-NEXT:    .cfi_def_cfa_offset 4144
+; RV64I-NEXT:    .cfi_def_cfa_offset 6176
 ; RV64I-NEXT:    lui a0, 1
 ; RV64I-NEXT:    add a0, sp, a0
 ; RV64I-NEXT:    call callee_stack_args
@@ -485,9 +485,9 @@ define void @reserved_call_frame(i64 %n) #0 {
 ; RV32I-NEXT:    lui a0, 1
 ; RV32I-NEXT:    sub sp, sp, a0
 ; RV32I-NEXT:    sw zero, 0(sp)
-; RV32I-NEXT:    .cfi_def_cfa_offset 4096
+; RV32I-NEXT:    .cfi_def_cfa_offset 6128
 ; RV32I-NEXT:    addi sp, sp, -80
-; RV32I-NEXT:    .cfi_def_cfa_offset 4176
+; RV32I-NEXT:    .cfi_def_cfa_offset 6208
 ; RV32I-NEXT:    lui a0, 1
 ; RV32I-NEXT:    addi a0, a0, 36
 ; RV32I-NEXT:    add a0, sp, a0