[PATCH] D114246: [RISCV] Fix a bug in RISCVFrameLowering.

[Hsiangkai Wang via Phabricator via llvm-commits]

HsiangKai created this revision.
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When we have out-going arguments passing through stack and we do not
reserve the stack space in the prologue. Use BP to access stack objects
after adjusting the stack pointer before function calls.

callseq_start  ->  sp = sp - reserved_space
//
// Use FP to access fixed stack objects.
// Use BP to access non-fixed stack objects.
//
call @foo
callseq_end    ->  sp = sp + reserved_space


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D114246

Files:
  llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
  llvm/test/CodeGen/RISCV/rvv/no-reserved-frame.ll


Index: llvm/test/CodeGen/RISCV/rvv/no-reserved-frame.ll
===================================================================
--- llvm/test/CodeGen/RISCV/rvv/no-reserved-frame.ll
+++ llvm/test/CodeGen/RISCV/rvv/no-reserved-frame.ll
@@ -5,42 +5,46 @@
 define signext i32 @foo(i32 signext %aa) #0 {
 ; CHECK-LABEL: foo:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    addi sp, sp, -64
-; CHECK-NEXT:    .cfi_def_cfa_offset 64
-; CHECK-NEXT:    sd ra, 56(sp) # 8-byte Folded Spill
-; CHECK-NEXT:    sd s0, 48(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    addi sp, sp, -80
+; CHECK-NEXT:    .cfi_def_cfa_offset 80
+; CHECK-NEXT:    sd ra, 72(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s0, 64(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s1, 56(sp) # 8-byte Folded Spill
 ; CHECK-NEXT:    .cfi_offset ra, -8
 ; CHECK-NEXT:    .cfi_offset s0, -16
-; CHECK-NEXT:    addi s0, sp, 64
+; CHECK-NEXT:    .cfi_offset s1, -24
+; CHECK-NEXT:    addi s0, sp, 80
 ; CHECK-NEXT:    .cfi_def_cfa s0, 0
 ; CHECK-NEXT:    csrr a1, vlenb
 ; CHECK-NEXT:    sub sp, sp, a1
 ; CHECK-NEXT:    andi sp, sp, -8
-; CHECK-NEXT:    lw t0, 36(sp)
-; CHECK-NEXT:    lw a2, 32(sp)
-; CHECK-NEXT:    lw a3, 28(sp)
-; CHECK-NEXT:    lw a4, 24(sp)
-; CHECK-NEXT:    lw a5, 20(sp)
-; CHECK-NEXT:    lw a6, 16(sp)
-; CHECK-NEXT:    lw a7, 12(sp)
-; CHECK-NEXT:    lw t1, 8(sp)
-; CHECK-NEXT:    lw t2, 4(sp)
-; CHECK-NEXT:    lw a1, 0(sp)
-; CHECK-NEXT:    sw a0, 44(sp)
-; CHECK-NEXT:    sw a0, 40(sp)
+; CHECK-NEXT:    mv s1, sp
+; CHECK-NEXT:    lw t0, 44(s1)
+; CHECK-NEXT:    lw a2, 40(s1)
+; CHECK-NEXT:    lw a3, 36(s1)
+; CHECK-NEXT:    lw a4, 32(s1)
+; CHECK-NEXT:    lw a5, 28(s1)
+; CHECK-NEXT:    lw a6, 24(s1)
+; CHECK-NEXT:    lw a7, 20(s1)
+; CHECK-NEXT:    lw t1, 16(s1)
+; CHECK-NEXT:    lw t2, 12(s1)
+; CHECK-NEXT:    lw a1, 8(s1)
+; CHECK-NEXT:    sw a0, 52(s1)
+; CHECK-NEXT:    sw a0, 48(s1)
 ; CHECK-NEXT:    addi sp, sp, -32
 ; CHECK-NEXT:    sd a1, 16(sp)
 ; CHECK-NEXT:    sd t2, 8(sp)
-; CHECK-NEXT:    addi a1, sp, 40
+; CHECK-NEXT:    addi a1, s1, 48
 ; CHECK-NEXT:    sd t1, 0(sp)
 ; CHECK-NEXT:    mv a0, t0
 ; CHECK-NEXT:    call gfunc at plt
 ; CHECK-NEXT:    addi sp, sp, 32
 ; CHECK-NEXT:    mv a0, zero
-; CHECK-NEXT:    addi sp, s0, -64
-; CHECK-NEXT:    ld s0, 48(sp) # 8-byte Folded Reload
-; CHECK-NEXT:    ld ra, 56(sp) # 8-byte Folded Reload
-; CHECK-NEXT:    addi sp, sp, 64
+; CHECK-NEXT:    addi sp, s0, -80
+; CHECK-NEXT:    ld s1, 56(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    ld s0, 64(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    ld ra, 72(sp) # 8-byte Folded Reload
+; CHECK-NEXT:    addi sp, sp, 80
 ; CHECK-NEXT:    ret
 entry:
   %aa.addr = alloca i32, align 4
Index: llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVFrameLowering.cpp
@@ -237,7 +237,13 @@
   const MachineFrameInfo &MFI = MF.getFrameInfo();
   const TargetRegisterInfo *TRI = STI.getRegisterInfo();
 
-  return MFI.hasVarSizedObjects() && TRI->hasStackRealignment(MF);
+  // If we do not reserve stack space for out-going arguments in prologue,
+  // we will adjust the stack pointer before call instruction. After the
+  // adjustment, we could not use $SP to access the stack objects for the
+  // arguments. Instead, use $BP to access these stack objects.
+  return (MFI.hasVarSizedObjects() ||
+          (!hasReservedCallFrame(MF) && (MFI.getMaxCallFrameSize() != 0))) &&
+         TRI->hasStackRealignment(MF);
 }
 
 // Determines the size of the frame and maximum call frame size.


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