[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.

Author: topperc

llvm/lib/Target/RISCV/RISCVFrameLowering.cpp

@@ -789,6 +789,8 @@ 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,
@@ -802,15 +804,15 @@ void RISCVFrameLowering::allocateStack(MachineBasicBlock &MBB,
 
       CurrentOffset += ProbeSize;
       if (EmitCFI)
-        CFIBuilder.buildDefCFAOffset(CurrentOffset);
+        CFIBuilder.buildDefCFAOffset(CurrentOffset + CFAAdjust);
     }
 
     uint64_t Residual = Offset - CurrentOffset;
     if (Residual) {
       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)

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