if (Offset != MFI.getObjectOffset(FI))
return false;
+ // If this is not byval, check that the argument stack object is immutable.
+ // inalloca and argument copy elision can create mutable argument stack
+ // objects. Byval objects can be mutated, but a byval call intends to pass the
+ // mutated memory.
+ if (!Flags.isByVal() && !MFI.isImmutableObjectIndex(FI))
+ return false;
+
if (VA.getLocVT().getSizeInBits() > Arg.getValueSizeInBits()) {
// If the argument location is wider than the argument type, check that any
// extension flags match.
--- /dev/null
+; RUN: llc < %s | FileCheck %s
+
+; Make sure we check that forwarded memory arguments are not modified when tail
+; calling. inalloca and copy arg elimination make argument slots mutable.
+
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i386-pc-windows-msvc19.0.24215"
+
+declare x86_stdcallcc void @tail_std(i32)
+declare void @capture(i32*)
+
+define x86_thiscallcc void @inalloca(i32* %this, i32* inalloca %args) {
+entry:
+ %val = load i32, i32* %args
+ store i32 0, i32* %args
+ tail call x86_stdcallcc void @tail_std(i32 %val)
+ ret void
+}
+
+; CHECK-LABEL: _inalloca: # @inalloca
+; CHECK: movl 4(%esp), %[[reg:[^ ]*]]
+; CHECK: movl $0, 4(%esp)
+; CHECK: pushl %[[reg]]
+; CHECK: calll _tail_std@4
+; CHECK: retl $4
+
+define x86_stdcallcc void @copy_elide(i32 %arg) {
+entry:
+ %arg.ptr = alloca i32
+ store i32 %arg, i32* %arg.ptr
+ call void @capture(i32* %arg.ptr)
+ tail call x86_stdcallcc void @tail_std(i32 %arg)
+ ret void
+}
+
+; CHECK-LABEL: _copy_elide@4: # @copy_elide
+; CHECK: leal {{[0-9]+}}(%esp), %[[reg:[^ ]*]]
+; CHECK: pushl %[[reg]]
+; CHECK: calll _capture
+; ...
+; CHECK: calll _tail_std@4
+; CHECK: retl $4