https://github.com/eleviant created
https://github.com/llvm/llvm-project/pull/177408
Wnen argument on stack needs to be zero extended, we can't omit ld/st pair,
because we may get an undefined value in certain conditions. (e.g the code
below will print 0xFFFFFFFF00000042 instead of 0x42)
```
[[gnu::noinline]]
void baz(int, int, int, int, int, int, int, int, long v)
{
printf("Value of v: %#lx\n", v);
}
[[gnu::noinline]]
void bar(int i1, int i2, int i3, int i4, int i5, int i6, int i7, int i8,
unsigned v)
{
baz(i1, i2, i3, i4, i5, i6, i7, i8, v);
}
[[gnu::noinline]]
void foo(int=1, int=2, int=3, int=4, int=5, int=6, int=7, int=8, uint64_t
dummy=-1ULL)
{
bar(1, 2, 3, 4, 5, 6, 7, 8, 0x42)
}
```
>From c4e2e3dd339436acb8000ea9e253972a14da3d00 Mon Sep 17 00:00:00 2001
From: eleviant <[email protected]>
Date: Thu, 22 Jan 2026 17:39:04 +0100
Subject: [PATCH] Don't skip storing stack arguments in case of size mismatch
(#177360)
Wnen argument on stack needs to be zero extended, we can't omit ld/st
pair, because we may get an undefined value in certain conditions. (e.g
the code below will print 0xFFFFFFFF00000042 instead of 0x42)
```
[[gnu::noinline]]
void baz(int, int, int, int, int, int, int, int, long v)
{
printf("Value of v: %#lx\n", v);
}
[[gnu::noinline]]
void bar(int i1, int i2, int i3, int i4, int i5, int i6, int i7, int i8,
unsigned v)
{
baz(i1, i2, i3, i4, i5, i6, i7, i8, v);
}
[[gnu::noinline]]
void foo(int=1, int=2, int=3, int=4, int=5, int=6, int=7, int=8, uint64_t
dummy=-1ULL)
{
bar(1, 2, 3, 4, 5, 6, 7, 8, 0x42)
}
```
---
llvm/lib/Target/AArch64/AArch64ISelLowering.cpp | 2 +-
llvm/test/CodeGen/AArch64/tail-call-stack-args.ll | 13 +++++++++++++
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
index bde4ba993f69e..a16f838eeaa40 100644
--- a/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -8833,7 +8833,7 @@ static bool shouldLowerTailCallStackArg(const
MachineFunction &MF,
if (CallOffset != MFI.getObjectOffset(FI))
return true;
uint64_t SizeInBits = LoadNode->getMemoryVT().getFixedSizeInBits();
- if (SizeInBits / 8 != MFI.getObjectSize(FI))
+ if (SizeInBits != VA.getValVT().getSizeInBits())
return true;
return false;
}
diff --git a/llvm/test/CodeGen/AArch64/tail-call-stack-args.ll
b/llvm/test/CodeGen/AArch64/tail-call-stack-args.ll
index 9ea516f930723..bbeea28f18bda 100644
--- a/llvm/test/CodeGen/AArch64/tail-call-stack-args.ll
+++ b/llvm/test/CodeGen/AArch64/tail-call-stack-args.ll
@@ -65,3 +65,16 @@ define void @wrapper_func_i8(i32 %a, i32 %b, i32 %c, i32 %d,
i32 %e, i32 %f, i32
tail call void @func_signext_i1(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32
%f, i32 %g, i32 %h, i32 %i, i1 signext %j)
ret void
}
+
+declare void @func_i64(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f, i32 %g,
i32 %h, i32 %i, i64 %j)
+
+define void @wrapper_func_i64(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f,
i32 %g, i32 %h, i32 %i, i32 %j) {
+; CHECK-LABEL: wrapper_func_i64:
+; CHECK: // %bb.0:
+; CHECK-NEXT: ldr w8, [sp, #8]
+; CHECK-NEXT: str x8, [sp, #8]
+; CHECK-NEXT: b func_i64
+ %conv = zext i32 %j to i64
+ tail call void @func_i64(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f, i32
%g, i32 %h, i32 %i, i64 %conv)
+ ret void
+}
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