This program:
target triple = "riscv64-unknown-linux-gnu"
define void @f(i64 %n) #0 {
entry:
%v = alloca i32, i64 %n, align 4
call void @g(ptr %v, [3000 x i64] poison)
ret void
}
declare void @g(ptr, [3000 x i64])
attributes #0 = { uwtable "frame-pointer"="none" "probe-stack"="inline-asm" }... generates the following output on Clang 22.1.3 for riscv64-unknown-linux-gnu:
$ clang --version
clang version 22.1.3
Target: loongarch64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
$ clang -target riscv64-unknown-linux-gnu -O2 -S -o - /tmp/rv-clash-prot.ll
.attribute 4, 16
.attribute 5, "rv64i2p1_m2p0_a2p1_f2p2_d2p2_c2p0_zicsr2p0_zmmul1p0_zaamo1p0_zalrsc1p0_zca1p0_zcd1p0"
.file "rv-clash-prot.ll"
.text
.globl f # -- Begin function f
.p2align 1
.type f,@function
f: # @f
.cfi_startproc
# %bb.0: # %entry
addi sp, sp, -16
.cfi_def_cfa_offset 16
sd zero, 0(sp)
sd ra, 8(sp) # 8-byte Folded Spill
sd s0, 0(sp) # 8-byte Folded Spill
.cfi_offset ra, -8
.cfi_offset s0, -16
addi s0, sp, 16
.cfi_def_cfa s0, 0
slli a0, a0, 2
addi a0, a0, 15
andi a0, a0, -16
sub a0, sp, a0
lui a1, 1
.LBB0_1: # %entry
# =>This Inner Loop Header: Depth=1
sub sp, sp, a1
sd zero, 0(sp)
blt a0, sp, .LBB0_1
# %bb.2: # %entry
mv sp, a0
lui a1, 5
sub t1, sp, a1
addi sp, sp, -2048
addi sp, sp, -1424
sd zero, 0(sp)
call g
lui a0, 6
addi a0, a0, -624
add sp, sp, a0
addi sp, s0, -16
.cfi_def_cfa sp, 16
ld ra, 8(sp) # 8-byte Folded Reload
ld s0, 0(sp) # 8-byte Folded Reload
.cfi_restore ra
.cfi_restore s0
addi sp, sp, 16
.cfi_def_cfa_offset 0
ret
.Lfunc_end0:
.size f, .Lfunc_end0-f
.cfi_endproc
# -- End function
.section ".note.GNU-stack","",@progbits
.addrsigNote that the second stack probing loop is incomplete, leaving sp half-updated and thus higher than it should be:
# %bb.2: # %entry
mv sp, a0
lui a1, 5
sub t1, sp, a1
addi sp, sp, -2048
addi sp, sp, -1424
sd zero, 0(sp)
call gThis is because PrologEpilogInserter only scans SaveBlocks for stack probe insertion, thus all PROBED_STACKALLOC pseudoinstructions in non-entry blocks are discarded. See #195454 (comment)
|
for (MachineBasicBlock *SaveBlock : SaveBlocks) |
|
TFI.inlineStackProbe(MF, *SaveBlock); |
This program:
... generates the following output on Clang 22.1.3 for
riscv64-unknown-linux-gnu:Note that the second stack probing loop is incomplete, leaving
sphalf-updated and thus higher than it should be:This is becauseSee #195454 (comment)PrologEpilogInserteronly scansSaveBlocksfor stack probe insertion, thus allPROBED_STACKALLOCpseudoinstructions in non-entry blocks are discarded.llvm-project/llvm/lib/CodeGen/PrologEpilogInserter.cpp
Lines 1184 to 1185 in fd51c78